Theses and dissertations (Applied Sciences)

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Sugar-sweetened beverages and household sugar consumption patterns among adults living in Southgate, Phoenix
(2024-09) Nene, Sindisiwe Portia; Naicker, Ashika; Singh, Evonne
Background: The Health Promotion Levy (HPL) was implemented in South Africa in 2018 as an intervention to decrease sugar consumption. While the link between excessive sugar consumption and dietary risk factors is well established, there is limited conclusive evidence that fiscal policy measures like the HPL can reduce sugar consumption and lead to favourable health outcomes. Aim: To determine the current sugar-sweetened beverage (SSB) and household sugar consumption patterns among adults in the Southgate Phoenix area. Methods: This study adopted both desktop and quantitative methods through a cross-sectional study. The desktop study included a scoping review using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The aim of the scoping review was to investigate the implementation of the sugar tax by various countries and assess the effectiveness thereof. Data from a syndicated Euromonitor generated report on sales of SSBs in South Africa were reviewed. Using a validated questionnaire, quantitative methods were also used to gather data on the current SSBs and household sugar consumption patterns among 399 consenting adults living in the Southgate Phoenix area. Sugar threshold detection test (TDT) of different sugar solutions and sweetness preference of market samples of cola SSBs were determined through sensory evaluation among 98 consenting adults living in the Southgate Phoenix area. Results: The scoping review included 37 studies on sugar tax in 17 countries. Most studies, 37.8% (n= 14), were conducted in various United States of America (US) states, followed by Mexico (16.2% n= 6) and South Africa (10.8% n= 4). Just over half of the studies (51.4% n= 19) reported a reduction in sales volume of SSBs. A decrease in SSB consumption was reported by 37.8% (n= 14) studies, whilst 2.7% (n= 1) study reported both reduced sales and consumption of SSBs. Reduced body mass index/weight was reported in 8.1% (n= 3) of studies. Key results for the household sugar and SSB consumption showed that a significant 55.1% (n= 220) of households purchased brown sugar, p<0.001, while 44.9% (n= 179) purchased white sugar. A significant 92.0% (n= 367) of households purchased sugar monthly p<0.001. Households (65.5% n= 102) predominantly purchased sugar in 2kg packs, p<0.001. There was a significant correlation between income and purchasing frequency and the size of sugar packaging purchased by participants; those with higher income purchased sugar less frequently (rho= .187, p<0.001) and in smaller packaging (rho= -.145, p= .006). A significant 96% (n= 382) of participants used sugar in tea and coffee, p<0.001, while 58% (n= 230) added it to cereal. A significant 68.1% of the participants reported using either 1 or 2 teaspoons of sugar in their tea/coffee, χ2 (4) = 153.619, p<0.001. However, 32.9% (n= 131), 16.5% (n= 51) and 2.5% (n= 10) consumed three teaspoons, four teaspoons and more than four teaspoons in their tea and coffee, respectively. The Mann-Whitney test analysis showed that males added significantly more sugar in their tea/coffee than females, Z= -2.779, p=.005. The amount of sugar added to tea/coffee was negatively correlated with age, rho= -.186, p<0.001. Results also indicated that the consumption of tea or coffee with sugar was positively correlated with age (rho=.175, p<0.001), with older people consuming more servings of sugar-sweetened tea/coffee. Regarding the consumption of SSBs, a substantial 77% (n= 308) of participants indicated that they frequently consumed sugar-sweetened carbonated soft drinks. Flavoured water was the second most consumed category, with 32% (n= 129), followed by energy drinks at 24% (n= 96). The Pearson’s chi-square analysis indicated that significantly more females consumed flavoured teas than males, χ2 (1) = 5.568, p=.018. Furthermore, the Pearson’s chi-square analysis indicated that significantly more females consumed flavoured water than males, χ2 (1) = 12.983, p<.001. A significant 76% (n= 305) of participants reported consuming SSBs at home, p<0.001. The proportion of SSBs purchased positively correlated with age (rho=.150, p=.003), with older people being associated with buying larger sizes of SSBs. Results from the Pearson’s chi-square test showed that a notable proportion of 18-25-year-olds were unaware of the sugar tax, while a notable proportion of 26-35-year-olds were aware of this tax, χ2 (4) = 13.924, p= .008. For the preference test, 40.8% (n= 40) participants preferred Coo-ee and noted that it was the sweetest SSB, followed by Coke at 27.6% (n= 27), χ2 (3) = 19.653, p<.001. Results for TDT found that a significant 57.1% (n= 56) of participants preferred the yellow-dot-30g/1ltr sugar sample (p<.001); the reason given by a significant percentage of 62.2% (n= 61) for their selection was sweetness preference (p<0.001). A significant 48.4% (n= 16) preferred the orange-dot-0.3g/ltr sample the least (p= .001). This indicates that the sample population has a preference for higher rather than lower levels of sweetness in their SSBs. Conclusion: South Africa was the first African country to implement the sugar tax, so it is important to document the barriers, challenges, and other findings from inception. In this study, we found that sugar tax studies were mostly conducted in first-world countries, and emerging literature is available on the South African context. While the SSB industry has been regulated, its resulting impact on the consumption of SSBs and household sugar consumption remains an underexplored research area. Households also lack information pertaining to optimal sugar intake and the long-term health implications of exceeding such limits. Joint efforts with multiple initiatives and interventions could yield better results in combating obesity and reducing the burden of non-communicable diseases (NCDs). These initiatives should include nutrition education and HPL awareness campaigns, as well as current fiscal policies.
A comparative study of mesoporous nanohydroxyapatite bionanocomposite from eggshells and fish scales through a mechanochemical method
(2024-09) Mkhize, Sandile Cromwell; Mokhothu, Thabang H.; Onwubu, Stanley C.; Mdluli, Phumlane S.
Dental hypersensitivity [DH] is a common pain amongst dental patients with a high negative impact on the quality of life. The onset of DH is attributable to the demineralisation of tooth enamel from excessive consumption of acidic drinks and beverages. While different materials have been reported for DH management, the application of nanoparticles is suggested to be the future of DH management. Particularly, the remarkable properties of mesoporous silica and nanohydroxyapatite have promoted their use for DH management. These materials are often synthesized following the wet-chemical route. However, the use of toxic chemicals and the cost associated made these processes infeasible for DH management. Given the said concern, this study synthesises nanohydroxyapatite (nHAp) from eggshell and fish scale waste and modified it with mesoporous silica to create a bionanocomposite (MSN@nHAp) via the mechanochemical method. Part of the study inquiry was to comparatively assess the remineralisation characteristics of nano-hydroxyapatite (nHAp) extracted from waste eggshells and fish scales. A quantitative approach to experimental research design is adopted in this study which includes three phases. The first looks to develop nanocomposite using nano-sized hydroxyapatite and mesoporous silica, then characterise the nanocomposite formed. Phase identification of the crystals was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) applied to determine particle size and morphology. The second assesses the quality of the nanocomposite, its biocompatibility, and its toxicological characteristics. The third evaluates the remineralization capabilities of nHAp in occluding open dentin tubules. The mean values of the occluded area ratio in the SEM study were evaluated with one-way analysis of variance (ANOVA) with statistical software (IBM SPSS Statistics v28; IBM Corp), followed by a multi-comparison test with Bonferroni correction (α = .05). The validity of the study was achieved following SANS 1302 (2008) requirement for preparation, developing, and testing toothpaste. The reliability was determined via the reproducibility and repeatability of tests. Paper 1 investigated the remineralization and acid-resistant characteristics of nanohydroxyapatite produced from eggshell waste via mechanochemistry. Paper 1 established that nHAp was successfully produced from eggshell waste after 5 hr of milling. It was found that the produced nHAp (EnHAp) was effective in neutralizing common dietary acids. the nHAp showed complete occlusion of the dentin tubules. Manuscript 1 was based on the comparative assessment of the remineralization characteristics of Nano-hydroxyapatite extracted from fish scales and eggshells. Manuscript 1 established that nHAp extracted from eggshells (EnHAp) showed superior dentin tubule occluding characteristics than those of fish scales (FnHAp and mFnHAp). It was found that there were slight variations in physicochemical characteristics such as the Ca/P ratio, crystallinity, particle sizes and surface morphology of the nHAp extracted. Paper II reports on the invitro assessment of the acid resistance characteristics of mesoporous silica/nanohydroxyapatite (MSN@nHAp) biocomposite synthesised through the mechanochemical method. Paper II established that the MSN@nHAp exhibits superior acid resistance characteristics. In conclusion, the provided evidence shows that the mechanochemical method is a useful technique in the synthesis and surface modification of valuable biomaterials. The experimental finding provides a benchmark for further advance studies on utilizing natural nHAp in dentistry.
Synthesis and characterization of electrospun-based composite for the remediation of pharmaceutical pollutants in wastewater
(2024-09) Sigonya, Sisonke; Mokhothu, Thabang H; Makhanya, Talent R; Mayer, Paul M
Pharmaceutical pollutants, including non-steroidal anti-inflammatory drugs (NSAIDs) and antiretroviral drugs (ARVs), pose a significant threat to aquatic environments, necessitating effective remediation strategies. This comprehensive study delves into the efficacy of nanotechnological approaches, with a special focus on adsorption, in addressing the persistent issue of pharmaceutical pollution in wastewater bodies. The research covers the synthesis and characterization of a multi-template molecularly imprinted polymer (MIP) targeting key pharmaceutical compounds, namely naproxen, ibuprofen, diclofenac, emtricitabine, tenofovir disoproxil, and efavirenz, for extraction from contaminated water sources. Comparative analyses between the synthesized MIP and a commercial Solid Phase Extraction (SPE) cartridge showed comparative performance of the MIP and SPE cartridge in quantifying pharmaceutical compounds present in wastewater samples. The results highlighted both materials' consistent efficiency in the removal of pollutants, with selective pharmaceuticals exhibiting varying levels of removal efficiency during different treatment stages. Regressions analysis showcased high linearity (R2 values ranging from 0.9980 to 0.9999), alongside remarkable recoveries (90.9 % to 100 %) for the MIP and method detection limits (MDLs) ranging from (0.14-1.08 μg L-1) for all target pollutants. Recoveries for SPE samples ranged from (62 % to 98 %) with method detection limits at (0.7-4.68 μg L-1). The optimal conditions for efficient extraction of pharmaceutical compounds using the MIP were determined through a series of experiments, considering factors such as pH, mass, concentration, and contact time. Results showed high extraction efficiencies (>96%) and a notable adsorption capacity (>0.91 mg. g-1) for both ARVs and NSAIDs, confirming the MIP's potential for successful removal of these pollutants from wastewater. Additionally, adsorption kinetics were studied, revealing a second-order rate model and adherence to the Freundlich adsorption isotherm. Furthermore, this study incorporates synthesized MIP into the electrospinning technique, utilizing various polymer blends and optimized solvents to enhance the remediation process. The study explores the electrospun mats morphology, particularly those composed of polyvinyl alcohol (PVA) and polyethylene terephthalate (PET), examining their structural characteristics using techniques such as Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and adsorption time studies. Through merging advanced nanotechnological techniques with electrospinning methodologies, this study presents a robust framework for combating pharmaceutical pollutants in wastewater. The incorporation of the MIP into electrospun mats, coupled with in-depth material characterization and adsorption studies, emphasizes the potential of this innovative approach for environmental remediation and drug purification processes. This research contributes valuable insights into the effective removal and quantification of pharmaceutical pollutants, emphasizing the pivotal role of electrospinning technologies in addressing environmental challenges. In conclusion, this study sheds light on the potential of a multi-template MIP for the removal of ARVs and NSAIDs from contaminated water sources, showcasing its versatility and efficacy in enhancing water treatment processes, as well as its utility in drug purification and recovery processes. Overall, the research provides valuable insights into the complexities of pharmaceutical pollutant removal, emphasizing the significance of selecting appropriate extraction methodologies in wastewater treatment processes to ensure efficient and sustainable remediation practices.
Activation of n-octane using VOx/MgO catalysts prepared by a mixed fuel solution combustion synthesis method
(2024-09) Padayatchee, Samantha; Ntola, Pinkie; Friedrich, H.B.; Olivier, E.J.
Oxidative dehydrogenation (ODH) is an important chemical process used to produce various industrial fuels and building blocks, such as butadiene, styrene, and propylene. In this process, a catalyst facilitates the oxidation of hydrocarbons, leading to the removal of two hydrogen atoms and the formation of an olefin. This reaction has attracted significant attention due to its ability to generate high yields and low by-product formation, making it an environmentally sustainable approach for olefin production. However, ODH reactions face certain challenges that must be addressed to make them more efficient and viable for large-scale production. The major challenge in this process is the low selectivity for the formation of olefins, as side reactions lead to the formation of unwanted by-products. In addition, the catalyst employed should exhibit stability and maintain high levels of activity and selectivity under the specified operating conditions. In recent years, the solution combustion synthesis method (SCS) has emerged as a promising technique for producing highly active and stable catalysts for oxidative dehydrogenation. In the SCS method, a precursor solution is heated in a furnace to produce a high-temperature exothermic reaction that drives the formation of nanoscale particles. SCS has several advantages over traditional synthesis methods such as sol-gel and solid-state reactions. This includes its simplicity in eliminating the need for an inert atmosphere or subsequent calcination procedures. Additionally, it allows for precise control of the particle size, morphology, and composition, which can significantly influence the catalyst's performance. It is also a cost-effective technique as it uses simple and inexpensive chemicals as precursors. The nanoparticles created through SCS are characterized by their ability to bind to high surface areas and tailor their specific morphology, such as a highly porous structure or a specific crystal facet. This structural control can significantly impact the catalyst's performance, as it influences the catalyst's active sites and the reactant's diffusion and adsorption properties. In this study, VOx/MgO catalysts were synthesized using a solution combustion synthesis method with three fuel mixtures as reducing agents. The fuel mixtures comprised of urea/hydrazine hydrate (UR/HH), glycine/urea (GLY/UR), and glycine/hydrazine hydrate (GLY/HH). The catalysts were characterized using BET, XRD, ICP-OES, HR-TEM, TPR and TPD-MS. Catalytic testing was performed in a continuous flow fixed-bed tubular stainless-steel reactor, operated in a down-flow mode, using air as the oxidant and nitrogen as the diluent gas. Reactions were carried out over a temperature range of 350-450 °C with 5% feed and 350-450 °C at 12% feed. The gas flow rates were varied to attain gas hourly space velocities of 8000 h-1. The carbon to oxygen ratio was 8:2. The catalyst bed was maintained at a volume of 1 cm3 with pellet sizes ranging between 600 – 1000 um. The reaction product stream was analyzed using gas chromatographs, one fitted with a thermal conductivity detector, and the other with a flame ionization detector. The results obtained from this study demonstrated varying morphologies and surface areas for each catalyst. The VOx/MgO catalysts showed the distribution of vanadium on the surface of the support with an aggregation of VOx clusters at certain locations. The %V2O5 loading varied from 14 wt%- 14.9 wt%, which correlated with the SEM-EDS results. XRD and Rietveld refinement results demonstrated that the vanadium supported on MgO catalysts was present as biphasic constituents, with the predominant phase being attributed to the MgO periclase phase. The second phase was identified as the magnesium orthovanadate (Mg3(VO4)2), while the crystalline Mg2V2O7 magnesium pyrovanadate phase was only identified only in the GLY/UR catalyst. Further characterization was performed using TPR for redox properties and TPD-MS for acid-base properties. The GLY/UR and GLY/HH catalysts displayed a high H2 consumption, with two distinct reduction peaks followed by a high concentration of Brønsted acid sites of >100 µmole/g for both catalysts. Catalytic testing revealed that all three catalysts exhibited activity for the ODH of n-octane. The selectivity towards the desired products was dependent on the vanadium concentration and the phase composition of the catalysts. Octene isomers, aromatic compounds, cracked products and carbon oxides were identified in the product stream. The GLY/HH catalyst displayed the best selectivity of 66% towards the formation of octenes. A decrease in feed concentration from 12% to 5% led to an increase in octene selectivity, specifically at 450 oC. This confirmed that the selectivity and conversion depend on the reaction temperature, phase composition and morphology.
Intervention effect of food literacy on household food waste in the KwaDukuza municipality
(2024-09) Miti, Nosipho; Naicker, Ashika; Grobbelaar, Hendrina Helena
Background: Approximately one-third of the food produced for human consumption is lost annually across the global food supply chain. In South Africa, it is estimated that around 10.3 million tonnes of food are wasted each year. Despite food waste occurring at various stages of food production, individual households have been identified as the primary producers of food waste at the consumption stage, driven by consumer behaviour and practice. While food waste is a global concern, South Africa's household food waste mimics that of developed countries. Although household food waste studies in South Africa have gained momentum, nearly all studies focus on household food waste consumer practices. No intervention study has been conducted to change consumer behaviour towards household food waste in South Africa. Likewise, the cost of household food waste, nutritional losses, and the environmental impact of household food waste have yet to be explored through an intervention. Interventions that target a change in human behaviour towards reducing household food waste can make a meaningful impact on food and nutrition security, and the environment. Aim: This study aimed to determine the intervention effect of food literacy on household food waste in the KwaDukuza municipality. Methods: In this randomised control trial (RCT), middle and high Living Standards Measure (LSM) households from five areas in the KwaDukuza municipality used in a formative study to determine household food waste behaviour and practices were eligible to participate in the study. All households at baseline received three colour-coded bins [used to separate food waste by food categories], binliners, food labels and freezer bags to contain cooked food waste. The first objective was to calculate household food waste through a weighed food waste audit at baseline and endline. A weighed food audit was conducted at each household (n=180). Objective two of this study included calculating the cost, associated nutrient losses and environmental impact of household food waste using the results of the food waste audit at baseline and endline. The cost of household food wasted was analysed using the mean price of foods from retail stores in the study area to determine the cost (Rand value) of household food waste at baseline and end line. The nutrient losses were calculated using the South African Medical Research Council Food Finder 3 web-based software at baseline and endline. The environmental impact was calculated using the My Emission Footprint calculator for food wasted at baseline and endline. The third objective of this study was to determine the intervention effect on household food waste. Households were randomly assigned into three intervention groups, intervention 1 (n=60), intervention 2 (n=60), and the control group (n=60). Households who were part of Intervention 1 received the food literacy toolkit and food literacy lessons on how to reduce household food waste; households in intervention 2 received the food literacy toolkits only and were reliant on self-efficacy to use the toolkit and households that were part of the control group did not receive any intervention. Results: Findings from the food waste audit showed that at baseline, the total mean of household food waste produced by all households (n=180) in this study was 1.53 kg (1531.29 g) per week, decreasing to 0.31 kg (307.47 g) per household/ week at the endline. A significant reduction of household food waste was recorded post-intervention (average waste per household = 307.47 g) When household food waste was separated into categories of the type of food wasted, the fresh produce pre-intervention (average waste per household = 917.73 g) was significantly more than the fresh produce postintervention (average waste = 173.43g). Meat produce wasted pre- (average waste per household = 109.56g) also surpassed the meat produce wasted post- (average waste per household = 43.26g). The cooked food wasted pre- (average waste per household = 387.07 g) was significantly greater than the cooked food post- (average waste per household = 76.39 g)-. The cost of food waste for the whole group pre- (average waste per household = R145.57) was significantly more than the cost of food waste for the whole group post- (average waste per household = R39.75). In terms of the environmental impact, the pre- (average waste per household = 7664.13 gCO2e) exceeded the environmental impact post- (average waste per household = 6407.67 gCO2e). A high nutrient loss from household food waste was recorded at baseline, and there was a significant reduction of macro-and micronutrient nutrient loss at the endline for the whole group (n=180). In intervention 1, intervention 2 and the control group, most nutrient losses such as energy, total protein, total lipids, total carbohydrates, and total dietary fibre were greater during the pre-intervention phase compared to the post-intervention phase. In this RCT, a significant reduction of household food waste was observed for the whole group (n=180) and across intervention groups. Following the 6-week intervention duration, between intervention arms, there was no discernible difference in household food waste, economic loss, nutritional loss and environmental impact. However, for every intervention group, there was a substantial decrease in all measured outcomes from baseline to endline. The main reason for this result could be attributed to the fact that households probably perceived that they were being monitored through the food waste audit at baseline and endline, implying that sensitisation of communities to their actual household food waste can be an impactful intervention strategy to conscientise consumers to reduce their household food waste. Conclusion: This study shows a clear linkage between household food waste, nutrition, economic and environmental impact. The disposal of food waste from households has a substantial and wide-ranging effect on the food chain, leading to various economic, environmental, and social challenges. The social ramifications of food waste are enormous, given the striking difference between the significant amounts wasted in affluent households and the prevalent hunger and food insecurity in many communities. In order to create a food system that is more environmentally friendly and able to withstand challenges, it is crucial to focus on and decrease the amount of food wasted in households. This requires a combined initiative of educating consumers, implementing effective waste management practices, and enacting legislation that encourages responsible consumption.
The development of a novel universal coating for urological implants
(2024-09) Shongwe, Mduduzi Hurmprey; Kudanga, Tukayi
Urology employs various implants, such as urinary catheters, ureteral stents, and ureteral access sheaths (UASs), to manage diseases associated with the urinary tract system. These implants serve different purposes. For example, urinary catheters are primarily used to drain urine from the bladder, ureteral stents are used to keep the ureteral cavity open for urine passage, and UASs are used in expanding the ureteral cavity to facilitate the introduction of other devices. However, these implants pose challenges due to their invasive nature and inadequate biocompatibility, which can lead to uroepithelial tissue damage (caused by friction) and an increase in the risk of urinary tract infections (UTIs). Urinary tract infections, in turn, can cause blockages that limit the effectiveness of these implants. Therefore, several strategies are currently employed to address these challenges, mainly the use of lubricious hydrophilic polymeric coatings and antimicrobial agents. While some success has been achieved, uroepithelial tissue damage and UTIs remain significant concerns. Furthermore, most of these strategies are tailored to specific urological fabricating materials, limiting their scope. In light of these challenges, this study developed a universal coating technology using polydopamine (PDA) as a versatile primer and polyvinyl pyrrolidone (PVP) as a hydrophilic polymeric top layer loaded with iodine (I2) as an antibacterial agent to improve properties of urological implants. Urological implant fabricating biopolymers including polyurethane (PU) and polydimethylsiloxane (PDMS) were modified with a PDA/PVP coating technology and loaded with various concentrations of I2 (0.1%, 0.5% and 1% w/v). The ability of the coating technology to reduce the friction coefficient of urological biomaterials was evaluated by assessing its ability to introduce lubricity. Other biological effects that characterize the biocompatibility and antimicrobial activity of the coated samples were assessed using relevant standard ISO (International Organization for Standardization) and EUCAST (European Committee on Antimicrobial Susceptibility Testing) In vitro methods. The biocompatibility of the coating technology was assessed by determining their cytotoxicity with the XTT cytotoxicity assay using L292 cells while the brine shrimp lethality assay (BSLA) was carried out as a preliminary animal model study. Their genotoxicity was assessed with the Ames mutachromo assay carried out with Salmonella typhimurium T100 to detect base shift mutation. The antimicrobial activity of the coated technology was determined using the IS0 22196 assay with Escherichia coli (ATCC 25922), the EUCAST disk diffusion and broth microdilution assays with E. coli (ATCC 25922), Proteus mirabilis and the urinary catheter bridge microbial migration assay with E. coli (ATCC 43888). The novel coating technology was adaptable to urological implant fabricating biomaterials with different surface polarities including PDMS and PU. The polydopamine/polyvinyl pyrrolidonecoated biomaterials were observed to have improved lubricity (slipperiness rate of 5 s per 10 mm biomaterial-agar interaction) and the ability to absorb and trap fluids (0.088 ± 0.009 mg/cm2). The concentration of iodine solution (0.1%, 0.5% and 1% w/v) loaded in the coatings significantly influenced their biocompatibility and antimicrobial efficacy. The biocompatibility observations made in the BSLA were mostly in line with the XTT cytotoxicity assay. When an iodine concentration of 0.1% and 0.5% w/v was incorporated, the PDA/PVP-coated biomaterials were not toxic towards L292 cells and not lethal towards brine shrimp larvae after a 24 h exposure period. However, potential lethality towards brine shrimp larvae was only observed in the biomaterial loaded with 0.5% w/v after an exposure period of 48 h. The coated biomaterials without iodine were not toxic while those that were loaded with a concentration of 1% w/v iodine were toxic according to both the XTT assay and BSLA. All the PDA/PVP-coated biomaterial loaded with iodine (0.1%, 0.5% and 1% w/v) did not demonstrate base shift mutations in Ames muta-chrome assay. The ISO 22196 method demonstrated that the PDA/PVP-coated biomaterials loaded with at least 0.1% (w/v) iodine reduced E. coli (ATCC 43888) by at least 2 growth logs. The minimum inhibitory concentration (MIC) for the PU-PDA/PVP (0.1% I2) surfaces was determined to be 40 mm2/ml for E. coli (ATCC 2592) 0.5 McFarland standard. The broth microdilution showed that the MIC of extracts of the PU-PDA/PVP (0.5% I2) to be 3 cm2/ml and of PU-PDA/PVP (1% I2) to be 1.5 cm2/ml for E. coli (25922). However, only the extract of PU-PDA/PVP (1% I2) was effective against P. mirabilis at 3 cm2/ml. In the disk diffusion assay, the PU-PDA/PVP (0.1% I2) was only effective against E. coli (ATCC 25922) with a 1 mm zone of inhibition. The PU-PDA/PVP (0.5% I2) was effective against both E. coli (ATCC 25922) and P. mirabilis with 12.13 ± 1.53 mm and 8.5 ± 0.5 mm zones of inhibition, respectively. PU-PDA/PVP (1% I2) showed the highest zone of inhibition (16.25 ± 1.77 mm) against E. coli (ATCC 25922) and 13 ± 1 mm against P. mirabilis. In the catheter bridge microbial migration assay, E. coli (ATCC 43888) growth across the bridge was observed after 24 h for PDMS and PDMS-PDA/PVP without iodine incorporation, after 48 h for PDMS-PDA/PVP (0.1% I2) and PDMS-PDA/PVP (0.5% I2), and after 72 h for PDMS-PDA/PVP (1% I2). In addition, there was a positive correlation (P<0.05) between the concentration of iodine loaded in the PDA/PVP coated biomaterials and antimicrobial activity (disk diffusion assay) while a negative correlation with biocompatibility (XTT cytotoxicity assay) was observed. Overall, the research demonstrated that a PDA/PVP-coating technology is adaptable for urological biomaterials including PU and PDMS, introduces lubricity on the surface of the biomaterials, and when it is loaded with 0.5% w/v I2, the coating can inhibit the growth of bacteria that cause UTI without causing toxicity in model eukaryotic cells. Therefore, the PDA/PVP (0.5% w/v I2) coating is a promising strategy for improving us.
Development, validation and implementation of a sustainable, nutrition-sensitive agriculture toolkit to address food and nutrition insecurity in Lesotho
(2024-09) Mothepu, Lisebo; Napier, Carin E.; Naicker, Ashika; Duffy, Kevin Jan
Background: Global food prices continue to increase because of natural and humaninduced disasterssuch as climate change and war. As a result, poverty remainsrelatively high globally, especially in lower-middle-income countries such as Lesotho. Poverty in Lesotho is rated at 49.7% with a staggering 24% of the population experiencing extreme poverty, and it is mostly prevalent in rural areas. Out of the population of over 2 million, approximately half of the populace survives below the poverty-line, and 58, 000 people continue to experience food insecurity. Lesotho ranks at 121st out of 125 countries with sufficient data to calculate 2023 GHI scores. Thehigherthe rank theworse the hungerindex. The Global Hunger Index recorded Lesotho’s hunger score at 32.4. This is categorised as alarming on the scale ranging from low to extremely alarming. Lesotho has been grappling with chronic food insecurity, with 61% of the population affected living in rural areas and 39% affected living in urban areas due to climate challenges such as heavy rains. In summary, severe food insecurity, decrease agriculture production, poverty, poor nutritional status, and HIV/AIDS decrease the quality of life in Lesotho. Aim: The main aim of the research study was to develop, validate, and implement, a sustainable nutrition-sensitive agriculture toolkit with two programs: sustainable agriculture and sustainable nutrition-sensitive agriculture. The toolkit was developed for rural small-scale female family farmers to provide for household consumption and local small-scale commerce. The study further aimed to introduce and educate female farmers in agri-business and agro- processing through the use of Greenhouse tunnels underpinned by sustainable agriculture, sustainable local community food systems, and sustainable nutrition-sensitive agriculture to address food and nutrition insecurity and attempt to decrease hunger at the community, household, and individual levels. Methodology: The sample size was n=126 females participants residing in rural households in the district of Mohale’s Hoek, Lesotho. The sample population age ranged from 20 to over 60 years. In this randomised control trial (RCT), a combination of quantitative and qualitative methods were used. The quantitative data was used to determine the interaction between socio-economic conditions, nutritional variety, nutritional competence, food consumption patterns, food security status, and agricultural practices. The qualitative data collection used was an observational research method under naturalistic and controlled observation. This approach involved manipulating and controlling the experimental and intervention research variables to determine cause and effect relationships. The control group participants were from Maqoala n=63, and the intervention group participants were from Mpharane n=63. The toolkit was developed using relevant literature for addressing poverty, hunger, food insecurity and nutrition insecurity. In addition, the toolkit was also developed using the results obtained from the study through the administered questionnaires: sociodemographic, household hunger scale and household food insecurity access scale, nutrition knowledge and anthropometry measurements for nutritional assessment, food frequency, 24-hour food recall, agricultural and knowledge practices, preparation, and preservation practices. The toolkit comprised of two programs: sustainable agriculture and sustainable nutrition-sensitive agriculture. The toolkit was validated through the Delphi method. The intervention was run for two years, to target three planting and harvesting seasons in both the control and experimental villages. Both the experimental and control group were allocated Greenhouse tunnels with irrigation systems, temperature control systems, storage facilities and food preparation facilities. The inputs given to each group included the allocation of inputs was seedsthat were certified by the government of Lesotho:round cabbage,spinach (Swiss chard), green beans (snap beans), red beetroot, carrots (Nantes), red bell pepper, tomato (stupice), butternut squash, potato (Vivaldi), and brown onion. The experimental group was given the researcher’s training manual together with the participants training manual. The experimental group was further trained using the manual. The control group, Maqoala, was given the training manuals, without any training. Results: Results indicated that all female participants (n=126) headed the households and were caregivers who resided with other people in the households. The majority of the households (61.9%) had one room, 16.7% had two rooms, and 11.9 % had three rooms with no electricity or running water in the houses. Notably, all participants were unemployed, and experienced anxiety over running out of food before having money to buy more. Almost 44% of the participants often had a shortage of money to buy food, and 45.2% of the participants sometimes had a shortage. The average monthly spending on food for 25.4% of the households was R201 to R300, whilst 36.5% of the households on average spent a between R301 to R400 on food each month. All the participants reported having a change in food intake due to decreased accessibility. Moreover, all the participants indicated that they consumed less food than required and had to cut the size of the food served to children because there was not enough food available. An estimate 89.7% of the participants skipped meals because there was not enough food to eat. The nutrient analysis from the 24-hour food recall indicated dietary inadequacy in energy, protein, calcium, and vitamins A, B6, B12, C, and E. When assessing the dietary diversity, the participants consumed more cereals and starchy foods, as reflected by the high carbohydrate Dietary Reference Intakes (DRIs). The Body Mass Index (BMI) of 4.7% of the participants from Maqoala was in the underweight BMI range compared to 3.1% of participants from Mpharane. The outcomes could also be influenced by a lack of nutrition knowledge as the average knowledge was 52.0%, ranging from 38 to 69% in both Mpharane and Maqoala.The results highlighted high levels of hunger, food insecurity and nutrition insecurity among the participants. The results supported the development, validation, and implementation of the toolkit through the Delphi method. Firstly, the toolkit focused on sustainable agriculture, planting vegetables, selling vegetables to generate money to buy seeds for the subsequent planting phases, and consumption and preservation of vegetables for households in the control and experimental groups. The intervention results indicated that Mpharane (experiment group) participants in phase 1, harvested 468 cabbage heads, sold 278 heads, and preserved 189 heads for household consumption. In phase 2, the number of cabbages increased to 612 heads; the participants sold 422 heads and preserved 189 heads for household consumption. In phase 3, 675 cabbage heads were harvested, 485 heads were sold, and 189 were preserved for household consumption. Mpharane had an increase of 144 heads of cabbage from phase 1, 468 heads of cabbage, to phase 2, 612 heads of cabbage, and in phase 3 (675 heads of cabbage), the increase was very low, with 63 heads of cabbage between phase 2 to phase 3. Maqoala (control group) participants did not sell any of the fresh produce they harvested. Instead, they shared the harvested fresh produce with each other. In phase 1, 567 cabbage heads were harvested, and 567 heads were shared among the n=63 participants for household consumption. In phase 2, the number of cabbage heads harvested increased to 627 heads and all 627 heads were shared among the participantsfor household consumption. In phase 3, 414 cabbage heads were harvested, and 414 heads were shared among the n=63 participants for household consumption. Maqoala produced a total of 1608 heads of cabbage between phases 1, 2 and 3, and Mpharane produced a total of 1755 heads of cabbage between phases 1, 2 and 3, 147 heads of cabbage more than Maqoala. The participants from experimental group harvested 519 bundles of spinach in Phase 1. In Phase 2, 834 bundles were harvested, 329 bundles in Phase 1, 644 bundles in Phase 2 were sold, and 189 bundles were preserved for household consumption. The participants harvested 1238 bundles of spinach in phase 3, and 1048 bundles were sold, whilst 189 were preserved for household consumption. The participants in Maqoala harvested 857 bundles of spinach and used all 857 bundles for household consumption. The experimental group had a vast increase in the bundles of spinach produced in phase 3, with 1238 bundles of spinach compared to phase 1, with 468 bundles, whilst phase 2, produced 612 bundles. The total of the bundles of spinach produced by the experimental group was 2591 bundles between phases 1, 2, and 3, whilst the control group produced 2196 bundles of spinach between phases 1, 2, and 3. The experimental group produced 396 bundles more than the control group. The toolkit introduced and educated the experimental group on agriculture practices, nutrition, and developing market products. At the baseline immediately after the lesson, the participants were assessed and scored 54% in lesson 1, 66% in lesson 2 and 80% in lesson 3. At the endline, the participants were not taught again but were expected to remember the previous lessons and practices they had done during the intervention. There was a decrease in the participants'scores atthe endline. The participantsscored 43% in lesson 1, 32% in lesson 2 and 65% in lesson 3. Conclusion: The findings indicated that poverty contributes to hunger, food and nutrition insecurity, and triple burden of malnutrition: undernutrition and overnutrition, and micronutrient deficiency in Lesotho. Food and nutrition insecurity can be addressed by integrating sustainable agriculture and sustainable nutrition-sensitive agriculture. Agriculture holds significant potential as it can contribute to addressing the primary causes of nutritionrelated problems, enhance worldwide food accessibility and availability and improve family food security, nutritional value, salary, and female empowerment. For these reasons, a sustainable nutrition-sensitive agriculture toolkit for small-scale female farmers with agribusiness and agro-processing components was developed from the Lesotho data and shown to improve household vegetable production and consumption. Agrifood systems contribute to high employment of females worldwide. Agrifood systems also contribute more to the livelihoods of females compared to males, mainly in developing countries. Enriching females and ending genderinequality under agrifood systems can improve the lives of the females and their homes, decrease starvation, increase earnings and strengthen resilience.
A mucor circinelloides-based integrated biorefinery
(2024-09) Zininga, Johnson Tungamirai; Permaul, Kugen; Singh, Suren
ABSTRACT The utilization of agro-based waste residue is a prominent example for establishing a circular bioeconomy. When agro-based waste is used to replace commercial growth media in microbial fermentation processes, it becomes expedient that the implementation of the biorefinery concept becomes integrated as the microbial biomass and their metabolites will add to the product spectrum. This study demonstrates an integrated approach towards valorization of sugarcane bagasse and microbial biomass comprising of Mucor circinelloides ZSKP. A maximum reducing sugar recovery of 80.67 g/l was achieved after combining lignocellulosic pretreatment with saccharification. A low temperature, glycerol and ammonium phosphate pretreatment method was established, where glycerol pretreatment conditions were reduced to 150°C and almost a third of the initial duration. This strategy will potentially result in lower energy consumption costs, decreased release of inhibitors and lower water consumption. The ammonium phosphate-containing hydrolysate yielded 12.89 g/l of fungal biomass after fermentation to add to 20.8 g lignin from the delignification step. Sequential fermentations were performed by addition of Saccharomyces cerevisiae as a co-culture to produce biomass and ethanol. The initial aerobic M. circinelloides fermentation was followed by mixed culture anaerobic fermentation. Fermentation of M. circinelloides (3 days aerobic growth) and S. cerevisiae (5 days of anaerobic growth) generated a balanced biomass yield of 17.9 g/l and ethanol yield of 18.69 g/l. Ethanol production demonstrated effective utilization of bagasse hydrolysate and offered the possibility of concurrent production with biodiesel in this biorefinery. The mixed biomass gave a lipid yield of (3.72 g/l) and a chitosan yield of (1.84 g/l), The lignin infused glycerol plasticized chitosan biocomposite plastic had a 100% improvement in thermogravimetric properties with almost 50% more energy needed to increase the temperature of the material when compared to glycerol-only-plasticized biocomposite. The deproteination step in chitosan extraction was modified and replaced with a protein recovery step, with protein yield being improved to a maximum of 187.89 mg/g. The amino acid composition of the protein showed that it has a relatively high content of lysine making it suitable as an animal feed supplement. This study presents strategies to address feasibility concerns for production of fungal chitosan, biodiesel and bioethanol from lignocellulosic waste and realizing the goal of a circular bioeconomy.
Effectiveness of a canteen and a behavioural worksite intervention to lower cardiometabolic risk in South Africa
(2024-09) Singh, Evonne Shanita; Naicker, Ashika; Grobbelaar, Heleen
Background: Chronic lifestyle diseases like type-2 diabetes, hypertension and dyslipidaemia are modifiable; however, these non-communicable diseases (NCDs) are set to outpace communicable diseases in South Africa. The South African population has a high prevalence of NCDs, including genetic lipid disorders, diabetes and hypertension, meaning that the risk for undiagnosed conditions, like prediabetes and prehypertension, to develop to diabetes and hypertension, respectively, is high. As employees spend much of their waking hours at work, an opportunity exists to engage with this subset of the population for targeted NCD reduction goals. This study used the worksite setting as a backdrop for the implementation of targeted interventions aimed at reducing employee cardiometabolic risk. The resulting gains have economic significance for the employee, the employer, and the country. It also has direct potential to improve employees' quality of life. Aim: To measure the effectiveness of a canteen and behavioural intervention versus a canteen-only intervention among participants by evaluating the change in number of individuals reaching two or more cardiometabolic risk goals, namely reductions in blood pressure, triglycerides, and glycated haemoglobin (HbA1c) - the primary outcome, and through changes in secondary outcomes including rates of type-2 diabetes prevalence and regression to normoglycemia and changes in anthropometry, lipids, and glucose. Methodology: This two-arm randomised controlled trial (RCT) featuring a canteen and behavioural arm (CB) and a canteen-only arm (CO), was structured to provide a six-week intervention to employees at two multinational companies spread across eight worksites. Prior to randomisation, all employees were informed about the pending study through information packs distributed at employee staff meetings and during promotional visits to worksites. The information packs contained details on the study, the purpose, duration, partners, expectations, and privacy clause. A two-step screening process was followed to recruit eligible employees for the study. In step one, consenting employees from the eight worksites were screened for inclusion in the study using an eight-question survey. In step two, eligible participants from step one underwent clinical tests (HbA1c, lipids and blood pressure measurements). Consenting employees who were either prediabetic or prehypertensive completed the baseline assessments, which included anthropometry, a demographic and lifestyle survey, a dietary questionnaire, the Global Physical Activity Questionnaire (GPAQ) and the 24-hour food recall. Participants were randomised to the CB and CO treatment groups. The CO group received six weeks of canteen intervention (changes to enable a healthy food environment). In comparison, the CB group received six weeks of canteen intervention along with a behavioural intervention. The CB intervention included an intense six-week lifestyle programme based on the Diabetes Prevention Programme (DPP). The lifestyle classes were held two days per week at each worksite, with three time slots per day to facilitate employee attendance. After the intervention period, a post-test was used to repeat the clinical tests (HbA1c, lipids and blood pressure measurements), measurements for anthropometry and the 24- hour food recall. Data were analysed to assess the effectiveness of the CB and the CO intervention on cardiometabolic risk factors among prediabetic and prehypertensive employees. Diet quality was assessed through the dietary quality questionnaire (DQQ) indicators, and the Framingham Risk Score was used to calculate participants' 10-year risk for developing cardiovascular disease (CVD). Results: Out of a potential pool of 3000 employees, 797 employees participated in the screening process. After applying exclusion criteria and obtaining consent, 147 employees agreed to participate in the RCT. Of these, 72 were assigned to the CB arm, and 75 to the CO arm. In this study, success was defined by a systolic blood pressure decrease ≥ 5mmHg, a decrease in plasma triglycerides ≥0.1 mmol/L and a decrease of ≥0.5% in HbA1c. In the CO intervention arm, twenty-two participants met no improvement of cardiometabolic risk factors while 29 (19.7%) participants met one, 23 (15.6%) participants improved two; and one (0.68%) participant improved all three cardiometabolic risk factors. In the CB intervention group, 21 (14.2%) participants met no improvement of cardiometabolic risk factors, 38 (25.8%) participants improved one risk factor, 13 (8.8%) participants improved two, and none improved three cardiometabolic risk factors. To evaluate the effectiveness of the CO arm on diabetes risk, 6 (4.0%) participants met the intended intervention effect; however, 69 (46.9%) did not. From baseline (BL) to endline (EL), 2 (1.3%) participants were diagnosed as diabetic, 20 (13.6%) participants presenting with prediabetes at BL increased to 23 (15.6%) presenting with prediabetes at EL and finally, 53 (36%) participants without diabetes decreased to 50 (34%) at EL. To measure the effectiveness of a CB intervention on diabetes risk, 6 (4%) participants met the intended intervention effect however, 66 (44.8%) did not. From BL to EL, 1 (0.68%) participant was diagnosed as diabetic, 22 (14.9%) participants at BL increased to 26 (1.6%) presenting with prediabetes and finally, 49 (33.3%) participants without diabetes decreased to 45 (30.6%) at EL. To evaluate the combined effect of a CB intervention versus a CO intervention on diabetes risk, 12 (8.1%) participants met the intended intervention effect; however, 135 (95%) did not. Overall, post intervention improvements were noted for the whole group when no targeted cutoffs were applied, meaning that these participants improved their risk factors but not within projected reduction cutoffs. Conclusion: Cardiometabolic risk factors were improved for some participants using CB or CO interventions at worksites. Given that the CB and CO interventions produced similar results, the CO intervention has the potential to have a broader reach across the entire worksite, regardless of employees' health conditions, as most employees engage with the worksite food environment (canteens, board room meals, tea stations). Promoting an enabling worksite food environment is likely to encourage healthy eating habits. Unlike the CB intervention, which is more resource-intensive, the CO intervention is more feasible to implement. These results were achieved under a challenging COVID-19 lock-down period through the implementation of a 6-week intervention. There is potential to improve these outcomes outside the influence of COVID-19 and by using a longer duration intervention. Collectively, improved employee health has gains for the organisation, their employees and the country. Scope also exists to improve the effectiveness of the outcome outside of a research study and through more integrated communication and support from the different role players, including human resources, shift supervisors, management, occupational health staff and through the election of employee health champions.
Ion doped metal oxide and its power conversion efficiency influence on Perovskite solar cells
(2024-09) Reddy, Dwayne Jensen; Lazarus, Ian Joseph
ABSTRACT Ion Doped Metal Oxide and its Influence on the Power Conversion Efficiency of Perovskite Solar Cells Dwayne Jensen Reddy Doctor of Applied Sciences This study focuses on the fabrication and characterization of Zinc-doped Titanium dioxide (ZnTiO2) as an Electron Transport Layer (ETL) in CH3NH3PbI3-based perovskite solar cells (PSCs). A one-step spin coating technique under controlled ambient conditions (relative humidity < 65%, room temperature ∼ 20oC ) for the development of PSC was applied to investigate the effects of Zn-ion doping on the structural, morphological, optical, and photovoltaic properties. Numerical simulations using SCAPS 1D were additionally performed to further investigate the influence of ion doping on the power conversion efficiency (PCE) of PSCs. Zn-doped TiO2 was successfully incorporated into the TiO2 crystal structure using the solgel technique. Characterization through X-ray diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDX) confirmed the incorporation of Zn ions. The crystallite size ranged from 19.99 to 7.1 nm, depending on the Zn ion doping concentration. XRD results also indicate the formation of a highly crystalline tetragonal perovskite (CH3NH3PbI3) phase. Fourier Transform Infrared (FTIR) spectroscopy verified the presence of the anatase phase of Zn-doped TiO2, while the formation of the adduct of Pb2 with dimethyl sulfoxide (DMSO) and methylammonium iodide (MAI) was confirmed at 1015 cm-1. Scanning Electron Microscope (SEM) images exhibited fairly smooth and uniform surface coverage for the Zn-doped TiO2 layers. The Root Mean Square (Rq) values for surface roughness showed a decrease from 26.85 nm for undoped TiO2 to 23.4 nm for the 5 mol% Zn-doped TiO2 layer. UV-Vis spectroscopy demonstrated low light transmission loss characteristics from 300 to 790 nm, with the 2 mol% Zn-doped TiO2 showing slightly improved light transmission between 550 and 800 nm. The bandgap energy of undoped and Zn-doped TiO2 ranged from 3.53 to 3.38 eV, while the perovskite layer exhibited a bandgap energy of 2.06 eV. Experimentally, an optimum PCE of 5.67% was achieved with a 2 mol% dopant concentration. However, increasing the Zn dopant to 5 mol% led to a slight deterioration in the PCE. Numerical simulations revealed that increasing the donor doping concentration in the ETL improved the conduction band alignment at the ETL and perovskite interface, resulting in a PCE of 6.17%. Optimizing the absorber acceptor doping concentration and band gap improved the PCE to 10.79%, however, created a pronounced conduction band offset at the ETL/perovskite interface. This was mitigated by introducing an interfacial layer of Cubic Silicon Carbide (3C-SiC) between the absorber and ETL to minimize the conduction band offset, ultimately achieving a PCE of 12.09%.
Oxidative dehydrogenation of n-octane using dealuminated faujasite zeolites
(2024-09) Mpotulo, Archie Sifundo; Friedrich, HB; Ndlela, SS
Commercially obtained NaY was modified by a dealumination process using different solutions containing specific concentrations of citric acid, ethylenediaminetetraacetic acid disodium (EDTA-2Na), and a mixture of both EDTA-2Na and citric acid. The three prepared catalysts were then used to study the effect of dealumination on oxidative dehydrogenation (ODH) of n-octane. Dealumination was carried out to strengthen the zeolites acid sites, which will lead to an increased activity towards the oxidation of n-octane. Results from these showed that removing the framework and extra framework aluminium in the NaY zeolites increases the intrinsic acidity, which then led to increased conversion in the ODH of n-octane, with the catalyst prepared by the mixture of both EDTA-2Na and citric acid recording the highest conversion of just above 10 %. The conversion was ascribed to the removal of both the non- and framework aluminium, which leads to improved pore volumes and surface area. All the three prepared catalysts were mostly selective towards the carbon oxides (COx) products which was due to the absence of the ODH promoting metal. To induce the ODH promoting properties on the prepared catalysts (NaY[AL] for acid leaching using citric acid, NaY[CAT] for chelating agent treatment using EDTA-2Na and NaY[CT] for complex treatment using citric acid and EDTA-2Na), they were then further modified by introducing gallium using a modified ionic exchange procedure. Gallium has been shown by previous studies to be a promising ODH active metal. All the prepared catalysts were exchanged by 2 %wt of gallium which contributed to the increase of about 2 % for all the prepared catalysts when they tested were under similar ODH conditions with the first three batches of dealuminated NaY. The introduction of framework gallium also decreased side reactions such as the cyclization and cracking reactions, due to the reduction in medium to strong acid sites. The COx selectivity for the catalysts decreased from above 90 % to just below 85 %. This was not the case for the highest acidic NaY[AL], which showed no decrease in the COx selectivity. Though there was a slight improvement on the olefins selectivity after gallium introduction, COx production was still favoured by the catalysts. To mitigate this, barium, a basic metal was also introduced into the prepared Ga-NaY catalysts. Barium was also introduced using ionic exchange, and 1.5 %wt was introduced. Barium is known for inducing basic sites which facilitates the quick desorption of ODH products, leading to suppressed overoxidation. Due to subsequent ionic exchange procedures done on the catalysts, the morphology of the catalysts was altered, with the NaY zeolites losing their cubic shape and also clustering. The effect of Ba for all the catalysts was not much, as only BaGa-NaY[CT] showed a 4 % decrease in the COx activity. All the catalysts showed increased cracked products and oxygenates, but not much improvement in the olefins and aromatic products. The findings of this study showed that the behavior of the zeolite catalysts in the ODH of alkanes depends both on the physical and chemical properties of the catalyst. Acidity is a big factor when dealing with zeolites, as the activity and selectivity of the catalysts depends on the alteration of this feature. A high concentration of strong acid sites alone can activate the paraffin of interest, however Lewis acid sites induced by a reducible gallium metal are responsible for improved octene activity, selectivity and stability of the catalysts through the facilitation of coke burning on the surface of the catalyst.
The consumption, product compliance and manufacturer insights of plant-based foods in KwaZulu-Natal
(2024-09) Govender, Camilla; Naicker, Ashika; Makanjana, Onwaba
Background: The term plant-based diet focuses predominantly on the consumption of food from plants. A plant-based diet consists mainly of wholegrains, fruits, vegetables, legumes, nuts, seeds and may also include more processed food products made from these ingredients. Food is the single most powerful lever to optimise human health and environmental sustainability. A large body of work has emerged on the environmental impact of various diets. As per the findings of the Environmental Assessment and Reference Tool (EAT)-Lancet Commission, many studies have concluded that a diet rich in plant-based foods (PBFs) has improved health and also environmental benefits. This transition has led to a noteworthy increase in the demand for PBFs globally, and South Africa is no exception. Aim: This study aimed to determine the consumption, product compliance and manufacturer insights of plant-based foods in KwaZulu-Natal (KZN). Methods: This study used a mixed methods approach, namely, qualitative and quantitative research methodology. The first objective of this study was to determine the consumption of PBFs and identify barriers and facilitators influencing the adoption of plant-based diets through a consumer survey. The study's second objective was to document the scope of plant-based products in terms of availability through in-store and online observations that were available in KZN. All products were analysed to determine the scientific and regulatory compliance of plant-based products by analysing food labels according to the Foodstuffs, Cosmetic and Disinfectant Act (Act 54, 1972), R146 Regulation relating to the labelling and advertising of foodstuffs. The qualitative aspect of the study delved into the product development practices, trends and challenges of plant-based manufacturers in South Africa through key informant interviews. The adequacy of the diet among consumers (n=100) who consumed plant-based foods was assessed through two 24-hour food recalls and analysed for dietary adequacy. Results: Three hundred and eighty consumers participated in the online survey, of which 67.7% (n=259) of participants were women and 31.3% (n=120). Regarding the frequency of consumption of PBFs, 47% (n=180) of participants consumed PBFs between 2 to 3 times a week, 27.7% (n=106) of participants consumed PBFs daily, 17.2% (n=66) of participants consumed PBFs once a week, and 4.2% (n=16) of participants consumed PBFs once a month. A significant 63.4% (n=243) of participants indicated that they spend at most R60.00 on plantbased products, p<0.001. Using the binomial test to assess if any response option was selected significantly more than others, a significant number of participants (80% n=307) p<0.001, reported that they consumed PBFs for health reasons, followed by 37% (n=142) who reported that they consumed PBFs due to religious reasons. A significant 64% (n=245) and 58.5% (n=224) of participants reported that the most common format of plant-based meat alternatives that they consumed were burgers and sausages, respectively (p<0.001). The findings of this study also revealed that there are many challenges and barriers that are associated with the adoption of PBFs. This study found that 58.5% of participants (n=224) reported that PBFs were expensive (p<0.001), and 40.5% of participants (n=155) indicated that PBFs were limited and lacked variety. A comprehensive database of plant-based products (n=431) in the South African market was documented through in-store and online observations. Eighty-nine percent (n=386) of the products documented were manufactured in South Africa.. Regarding South Africa's labelling regulation, 95% (n=411) of the plant-based products complied with legislation. Key informant interviews were conducted with manufacturers to understand the market trends and constraints within the South African plant-based food sector. Key themes emerging from the key informant interviews included consumer-centric PBFs, consumer-driven plant-based trends, growth in the plant-based market, dynamic and evolving plant-based product development, challenges in PBF manufacture and marketability, insufficient government support and market-related price of PBFs. Furthermore, the adequacy of plant-based diets was analysed using the 24-hour food recall (n=92). The majority of nutrients fell below the EAR for both males and females. Both groups exhibited dietary inadequacies in specific micronutrients: vitamin D, folate, vitamin B12, and iron. Dietary inadequacy of specific micronutrients was noted for vitamin D, Folate, vitamin B12 and iron in both groups. However, there was notable carbohydrate excess intake across both groups and genders, surpassing the recommended estimate for energy. Conclusion: This study comprehensively examined the consumption patterns, product compliance, and manufacturer insights of PBFs in KZN. The findings reveal a growing interest in flexitarian diets and frequent consumption of PBFs, driven primarily by health motivations but hindered by cost and limited variety. Retail availability of PBFs in KZN is extensive, offering consumers a wide range of choices in both fresh and frozen categories, reflecting the robust state of the plant-based industry in KZN and it can be reasonably generalised to the whole country Regulatory compliance among PBFs is generally high, although small-scale manufacturers occasionally fall short of labelling standards. Manufacturer insights indicate a consumer-driven demand for PBFs that closely mimic meat products, necessitating innovation and regulatory support to stabilise this emerging market. Nutritional assessments of plant-based diets highlight a critical need for dietary supplementation to address deficiencies in essential vitamins and minerals such as B12, iron, and zinc. The study underscores the importance of nutrition education to guide consumers towards healthier food choices within plant-based diets. In conclusion, while the plant-based food sector in KZN is expanding and meeting many consumer needs, there are significant opportunities for improvement in product variety, affordability, regulatory compliance, and nutritional adequacy. Addressing these challenges through coordinated efforts among stakeholders can further enhance the adoption and benefits of plant-based diets. The conclusions drawn from this study can be reasonably generalised to metropolitan areas of the whole country.
Increasing catalytic activity of a fructosyltransferase using site-directed mutagenesis
(2024-05) Wang Fanzhi; Permaul, Kugen; Singh, Suren
Fructooligosaccharides (FOS) are naturally occurring metabolites that have a wide application in the food industry. They are one of the most well-studied prebiotics and have been used as an alternative sweetener to sucrose, as the modern diet demands healthier and calorie-reduced foods. FOS is commercially produced either by hydrolysis of inulin into inulin-type FOS or by sucrose transfructosylation into levantype FOS. The levan-type FOS are short-chain FOS and are produced under the catalysis of fructosyltransferase (FTase) or fructofuranosidase (FFase). In this study, FOS production was studied using a fructosyltransferase, SucC, which was originally isolated from Aspergillus niger and was functionally expressed in Pichia pastoris. The tertiary structure of SucC was determined by bioinformatics analysis and catalytic sites were verified and validated by wet and dry experiments where the amino acid residues D64, D194 and E271 were proved to form the catalytic triad. Three mutants, C66S, G273V, L313H were constructed aiming to improve the enzyme performance. Only the C66S mutant showed improved enzymatic activity which was 61% increase in specific activity. The other mutants, G273V and L313H, led to a complete loss of enzyme activity. By simulating saturated mutagenesis, tertiary structure alignment, and molecular docking, it was predicted that the C66S mutation could increase the hydrophilic environment surrounding the active site without visible changes in its structure. Two more amino acid residues (E296, H310) in addition to D64, D122, R193, D194, E271 in mutant C66S were predicted to be interacting with sucrose, and the binding energy changed from -3.65 to -4.14 kcal/mol. Subsequently, mutant C66S was constructed by site-directed mutagenesis and expressed in Pichia pastoris GS115. The purified mutant C66S showed improved enzymatic activity with a 61.3% increase in its specific activity. Its Km value was decreased by 13.5% while the kcat value increased by 21.6%. Its transfructosylation efficiency significantly improved during the initial reaction stages of FOS production. These results clearly revealed that the increase of hydrophilicity surrounding the active site enhanced the transfructosylating activities. Therefore, modification of the hydrophilic micro-environment surrounding the active site could be an alternative way to artificially evolve an enzyme’s catalytic efficiency.
Influence of storage conditions and sample processing on viral particle recovery from untreated municipal wastewater
(2024-05) Subroyen, Sueyanka; Bux, Faizal; Kumari, Sheena K.; Pillay, Leanne
The emergence and re-emergence of several epidemic and pandemic related pathogens has highlighted the need for the development and implementation of rapid and sensitive disease surveillance tools. Wastewater-based epidemiology (WBE) is one such environmental surveillance tool that has been adapted to provide a near real-time reflection of a population’s health dynamics through detecting and quantifying biomarkers from untreated wastewater. This information can be used to monitor disease progression, detect infection hotspots as well as emerging variants. The success of WBE, however, is determined by the accuracy of pathogen detection and quantification methods. Various factors, such as transportation, storage conditions, and wastewater characteristics can affect the quantification, leading to unreliable results. This study aimed at investigating the effects of storage temperatures on SARS-CoV-2 and influenza A degradation in raw wastewater samples and extracted nucleic acids. Additionally, different pre-treatment strategies for improving viral recovery from wastewater solids were also examined as part of the optimization process. Municipal wastewater influent was collected and stored at 25°C, 4°C, -20°C, and -80°C for 84 days. A control sample (spiked with attenuated viruses) was also stored under the same conditions. The viral RNA was extracted and quantified from both the samples (stored wastewater and control) every two weeks. Additionally, the physicochemical characteristics of the wastewater at different temperatures were evaluated for their possible impact on degradation. Supernatant samples and solid particles were used separately for RNA extraction and quantification to assess viral attachment to solid particles. Degradation of influenza A was observed in all samples with the highest at ±25°C in the supernatant (88.89%) and pellet (83.47%) of the wastewater influent, ±25°C in the spiked supernatant (90.69%) and 4°C in the spiked pellet (92.64%). The highest degradation of SARS CoV-2 was observed at ±25°C in the supernatant (94.1%) and pellet (92.66%) of the wastewater influent, 4°C in the spiked supernatant (95.57%) and -20°C in the spiked pellet (50.79%). The lowest degradation of SARS-CoV-2 in the spiked pellet was observed at ±25°C (44.82%) and 4°C (31.53%). This may be indicative of viral adhesion to wastewater solids. The assessment of the physicochemical characteristics indicated of changes in stored wastewater samples. Salinity, DO, pH, COD, TS, and TFS were correlated with viral degradation. pH was also found to be correlated with viral particles attaching to wastewater solids. The effect of storage temperature on stored RNA was also studied using the extracted RNA for a period of 168-days. The degradation between -20°C and -80°C was significantly different for RNA storage. The lowest degradation of SARS-CoV-2 occurred at -80°C (32.51% - wastewater influent; 33.42% - viral controls). In the case of influenza A, the lowest degradation occurred at -80°C for wastewater influent (43.28%) and -20°C for viral controls (36.02%). Statistical analysis conducted comparing storage of wastewater influent to extracted RNA indicated that degradation was higher in the wastewater samples. Additionally, to enhance viral recovery from wastewater solids, sodium pyrophosphate and ultrasonication were explored as pre-treatments strategies. SARS-CoV-2 concentrations in the supernatant were significantly increased between 3.30 - 35.65% by ultrasonication at frequencies ranging from 4 to 16 kHz, indicating that significant amounts of RNA may be attached to solid particles based on the contact time. These results highlight the importance of additional pre-treatment methods for maximizing RNA recovery from wastewater samples. The findings of this research may contribute significantly to the improvement of WBE detection methods for disease surveillance.
Development of electrochemical biosensors for sweeteners using engineered nanomaterials supported by computational modelling
(2024-05) Hloma, Phathisanani; Bisetty, Krishna; Sabela, Myalowenkosi Innocent; Uwaya, Gloria Ebube
Electrochemical immunosensors are a powerful tool in analytical applications. The current methods for the isolation and detection of artificial and natural sweeteners suffer from challenges in sample preparation and a lack of specificity. However, electrochemical immunosensors offer a sensitive, economical, and selective analytical solution to analyse these commonly used sweeteners, such as aspartame. The author of this work developed electrochemical immunosensors for the food and beverage industries to use in the detection and measurement of aspartame, a non-nutritive sweetener, and rebaudioside A, a natural sweetener. Most artificial sweeteners are low-calorie options that are suggested for ailments linked to health. These sweeteners' ability to remain stable at even high temperatures has greatly expanded the range of meals that can use them. Aspartame and rebaudioside A have not been linked to any health risks, although regulation is still necessary because of their extensive use in the food industry. The developed immunosensors for the detection of aspartame and rebaudioside A were achieved and presented as three case studies in this study. In the first case study, the immunosensor was achieved by fabricating green synthesized PVP capped silver nanoparticles (PVP-AgNPs) with functionalized multi-walled carbon nanotubes (fMWCNTs) and immobilizing the human sweet tase receptor T1R2 in a glassy carbon electrode (GCE), resulting in GCE/PVP-AgNPs/fMWCNTs/T1R2. The electrochemical assessment of aspartame was achieved using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV), respectively, under optimum pH 8 in a 0.1 M phosphate buffer with reference to the Ag/AgCl reference electrode. The electro-oxidation of ASP was noticed by a well-defined oxidation peak potential at 1.4 V. The immunosensor sensor showed a linear dynamic range of 2.89 to 27.61 μM (R 2 = 0.9170) based on differential pulse voltammetry, with limits of detection (LOD) and quantification (LOQ) (S/N = 3) of 0.40 μM and 1.34 μM, respectively. The second case study focused on the indirect electrochemical detection of rebaudioside A in the presence of ferro/ferricyanide as a redox probe. The immunosensor was developed by fabricating GCE with zeolitic imidazolate framework-67 (ZIF-67) in combination with fMWCNTs and the immobilization of the T1R2 receptor. The qualitative and quantitative analysis of rebaudioside A was done using CV, EIS, and DPV utilizing a 5 mM [Fe (CN)6] 3-/-4 redox probe. The stable electrode had an exponential dynamic range of 0.9901 µM to 8.2569 µM (R2 = 0.9996). The LOD and LOQ were computed to be 1.10 µM and 3.33 µM, respectively. This case study also used Patch Dock and PyRx to better understand the interactions between Reb A and T1R2. The final case study employed a platinum electrode (PtE) as the working electrode (WE) for the electrochemical immunosensing of aspartame. The modification of PtE involved the utilization of a nanocomposite consisting of PVP-AgNPs and reduced graphene oxide (rGO), with T1R2 immobilized. The electrochemical detection of aspartame was achieved under optimized conditions at pH 8 in a 0.1 M phosphate buffer, utilizing CV, EIS, and DPV as electrochemical tools. The PVP-AgNPs/rGO/T1R2 was used to fabricate Pt and the electrode performed well with a linear increase in oxidation peak currents as aspartame concentrations were increased from 2.38 µM to 25.78 µM (0.9529). The LOD and LOQ were calculated to be 5.85 µM and 17.73 µM, respectively. The synthesized nanoparticles and nanocomposites (PVP-AgNPs/fMWCNTs, ZIF 67/fMWCNTs, and PVP-AgNPs/rGO) were characterized using conventional techniques such as UV-Vis spectroscopy, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), field flow fractionation (FFF), single particle inductively coupled plasma mass spectrometry (sp-ICPMS), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). In addition to the experimental results, computational chemistry methods were undertaken. These included adsorption assessments, density functional theory (DFT), and molecular docking techniques. These techniques were all aimed at achieving a deeper molecular-level understanding of the interactions among the analytes (Aspartame and Reb A), T1R2, and the nanocomposites employed in the modification of the working electrodes (GCE and Pt-E)
The efficiency of lytic enzymes for Ascaris eggs inactivation
(2024-05) Zikalala, Thabiso; Stenström, Thor Axel; Amoah, Isaac Dennis; Buckley, Christopher Andrew
Faecal sludge (FS) contains organic matter that can enhance soil quality if pathogenic organisms, such as Ascaris lumbricoides, are reduced to safe levels. A. lumbricoides is a highly resistant nematode used to assess the efficiency of FS and wastewater treatment. The standard for reusing FS is to reduce Ascaris spp eggs to <1 egg/g for helminth reduction. However, in many developing countries, untreated FS is used as a soil enhancer without following proper guidelines. There are a number of FS treatment technologies in use, such as compositing, drying and the use of calcium carbonate. These techniques are able to reduce the pathogen concentration, especially Ascaris spp to accepted standard prior to application. Other alternative FS treatment technologies are under assessment and development. The objective of this study was to evaluate the use of lytic enzymes to inactivate Ascaris spp eggs by targeting the egg shell of the parasite. Ascaris spp egg shells consist of protein, chitin, and a lipid layer. Therefore, it may be possible to disintegrate Ascaris spp by targeting these layers of the egg shell with enzymes such as protease, chitinase, and lysozyme, which are commonly produced by indigenous soil bacteria. Ascaris spp eggs were detected in all FS samples collected from urine dehydration diversion toilets (UDDTs) in Durban, with an average concentration of 976-1118 helminth eggs/gram of FS. However, the viability of recovered eggs from FS was low and eggs were in different stages of development. This would negatively affect the experiments and produce inconsistent data. Therefore, for the lytic enzyme inactivation experiments, commercially bought eggs were used instead of the helminth eggs recovered from the UDDTs FS. Exposure of the eggs to commercial lytic enzymes was done following three different approaches. Firstly, Ascaris spp eggs were exposed to each of the enzymes individually, a second approach was employed where the eggs were consecutively exposed to the eggs with a rinse in between, and lastly, the eggs were exposed to a mixture of all three enzymes at once. Viability of the Ascaris spp eggs was determined via incubation, followed by microscopic examination of the eggs for visible motile larvae. For the single enzyme exposure, chitinase was the most detrimental enzyme resulting in a reduction of viability by 34% at room temperature. Exposure of the Ascaris spp eggs using the enzymes in series, achieved an egg viability reduction of up to 90 % at 37 °C, after 5 days exposure. Exposing the eggs to the mixed enzymes gave a reduced egg viability of 75 % at 37 °C, after 5 days exposure. Furthermore, the detection of microorganisms in the FS capable of producing lytic enzymes used was also confirmed. Enzymes were produced using selective media that resulted in the production of enzymes where the concentration (mg/L) and specific activity (U/mg) was determined to 0,68 mg/mL (0,08 U/mg) of protease from nutrient broth enriched with 2.5% milk, 3,17 mg/mL (0,006 U/mg) of chitinase produced from 1% colloidal chitin, and 7132 mg/mL (2600 U/mg) lysozyme from nutrient broth enriched with 1% Micrococcus lysodeikticus culture. The lytic enzymes showed to have an antagonistic effect on the Ascaris spp eggs. This therefore serves as a proof of concept that lytic enzymes produced by microorganisms found in FS could potentially be used for the inactivation of Ascaris spp eggs. However, further work is required focusing on enhancing the enzyme production, testing of the inactivation potential of these enzymes in the presence of solids and other materials present in FS, and finally the technique for field application of such technology.
Anticancer and anti-reactive oxygen species activity of bioactive peptides isolated from vigna unguiculata
(2024-05) Ramsookmohan, Sonaal; Mellem, John Jason; Dwarka, Depika
Cancer is a major cause of death globally and continues to escalate with current anticancer drugs associated with severe side effects and resistance driving the need for safer alternative therapeutics. Food proteins, from legumes, are a source of bioactive peptides and studies revealed that they are associated with various therapeutic properties. Cowpea (Vigna unguiculata) is an underutilized nutritious legume crop with promising potential due to its documented protein profile. Therefore, this study evaluated the in vitro anticancer effect of V. unguiculata peptides derived from alcalase and flavourzyme. Physicochemical properties such as water and oil absorption capacities, emulsifying properties, sub-unit composition, amino acid composition among others, were also assessed. Peptides were also evaluated for their antioxidant activity using superoxide radical scavenging, 1,1-diphenyl-2-picrylhydrazil (DPPH) and 2,2’-azino-bis (3 ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays as well as for their apoptotic potential using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), reactive oxygen species (ROS) and caspase 3/7 assays on cancerous (Caco-2 and MCF 7) and healthy (C2C12) cell lines. From results obtained it was observed that the foam capacity for the peptides derived from alcalase and flavourzyme were 78.34 and 82.39%, respectively, which was noted to be significantly different. The physicochemical properties determined their potential application in food industries. Glutamic acid was the most abundant amino acid in all samples while methionine was noted to be the least concentrated amino acid in the flour and alcalase derived sample while proline was the least concentrated in the flavourzyme sample. Results from this study suggest that cowpea samples have antioxidant capabilities with enzymatic hydrolysis contributing to a higher capacity compared to that of raw flour flour samples. From the cowpea flour, the peptide sample derived from alcalase demonstrated the highest DPPH free radical scavenging activity (70.88-80.47%), followed by flavourzyme (67.27-75.84%), while the raw flour sample showed the lowest activity (24.28-66.17%). The ABTS scavenging capacity of the alcalase peptide was in the range of 35.26-85.92%. The MTT cytotoxicity assay revealed that the cowpea peptides and camptothecin showed different sensitivities on the MCF-7 cell lines. The IC50 values of flavourzyme peptide, alcalase peptide and camptothecin were 0.07, 0.09 and 0.07 µg/mL respectively. Cell viability of the cowpea peptides and camptothecin (control) on the Caco-2 cells varied with the different concentrations. Alcalase and flavourzyme samples had IC50 values of 0.15 and 0.11 µg/mL respectively. The apoptotic potential of the peptides was further shown by the caspase 3/7 activity. From the results in this study, it can be ascertained that the cowpea peptides have potential as an anticancer therapeutic agent. Further research is necessary to determine mechanism of action and to conduct in vivo evaluations of these peptides using animal models
Development of electrochemical sensors for the detection of mycotoxins in food matrices using functionalised nanocomposites
(2024-05) Naidoo, Lyndon; Bisetty, Krishna; Meier, Florian; Uwaya, Gloria Ebube
The analysis of pathogens in foods is of critical importance to ensure consumer safety and quality assurance, as contaminants pose serious risks to public health. Mycotoxins are naturally occurring carcinogenic toxins that arise from specific strains of fungi as they contaminate food. They are found in a wide variety of grains, cereals, and dairy products, causing cancer in both humans and animals. Thus, there is a growing demand for simple, sensitive and inexpensive sensors for mycotoxin detection in lieu of conventionally employed large-scale instrumentation. In this study, the development of electrochemical sensors for the detection of aflatoxin B1 (AFB1), zearalenone (ZEN) and ochratoxin A (OTA) in foods was investigated and presented as three case studies, respectively. In the first case study, an ultrasensitive aptasensor was developed for the indirect detection of AFB1 in the presence of a ferri/ferrocyanide ([Fe(CN)6]3-/4-) redox probe solution. The sensor was constructed by immobilizing an anti-AFB1 aptamer (Apt) to a carboxylated multiwalled carbon nanotube (cMWCNT) and iron oxide (Fe3O4) nanoparticle (NP) composite using a glassy carbon electrode (GCE). This resulted in the development of the GCE/cMWCNTsFe3O4 NP/Apt sensor. An electrochemical response was exhibited from AFB1 applying cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV), respectively, utilizing a [Fe(CN)6]3-/4- redox probe prepared in phosphatebuffered saline (PBS) solution with reference to the Ag/AgCl reference electrode under optimized conditions. DPV findings reported very low limits of detection (LOD) and quantification (LOQ) of 0.43 fg mL-1 and 1.44 fg mL-1 respectively in comparison to current literature, over a calibration range of 0.50 fg mL-1 to 5.00 fg mL-1. For real sample analysis, excellent spike recoveries from 95% to 105% were obtained for corn and rice flour. Density functional theory (DFT) was used to propose a reaction scheme by ascertaining the electronic properties of the redox-active functional groups of AFB1. This supported the experimental anodic response findings of DPV. The second case study focused on how PEGylated Fe3O4 NPs and cMWCNTs fabricated on a GCE could be used for the design of an electrochemical sensor for ZEN analysis. The qualitative and quantitative analyses of ZEN were completed using CV, EIS and DPV, respectively, under optimized conditions in a sodium phosphate buffer solution. The developed sensor reported significantly low LODs and LOQs of 0.34 fg mL-1 and 1.12 fg mL-1 respectively, over a calibration range of 1.00 fg mL-1 to 10.00 fg mL-1 by DPV. Excellent spike recoveries ranging from 92% to 106% were obtained for rice and corn flour. The Monte Carlo (MC) adsorption simulation studies predicted the strong interaction of ZEN with the constructed sensor. In the final case study, an OTA electrochemical sensor was designed using a nickel metalorganic framework (Ni-MOF) and carboxylated reduced graphene oxide (cRGO) on a GCE. The detection of OTA was achieved under optimized conditions in PBS solution with the developed GCE/Ni-MOF/cRGO electrode, employing CV, EIS and DPV as electrochemical tools. Applying DPV, the sensor reported very low LODs and LOQs of 3.29 fg mL-1 and 10.97 fg mL-1 respectively, over a calibration range of 10.00 fg mL-1 to 90.00 fg mL-1. Regarding real sample analysis, excellent spike recoveries from 95% to 105% were obtained for corn and rice flour. Molecular dynamics (MD) studies predicted that the Ni-MOF exhibited a strong electrostatic interaction with the OTA analyte, in agreement with the experimental findings. The synthesized nanomaterials (cMWCNTs-Fe3O4 NP, PEG-Fe3O4 NPs/cMWCNTs, and NiMOF/cRGO) utilized in this study were characterized by an array of techniques, including single particle inductively coupled plasma-mass spectrometry (spICP-MS), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), multidetector asymmetrical flow field-flow fractionation (AF4), and Fourier transform infrared spectroscopy (FTIR). Finally, computational modelling studies were undertaken to establish a synergy with the experimental approaches employed in each case study. These methodologies included DFT, docking studies, MC adsorption and MD simulations, which were aimed at predicting and assessing the atomic and molecular interactions between the mycotoxins and their respective electrode systems.
Development of chitosan biopolymer films by fungal fermentation of waste substrates
(2024-05) Naidoo, Krinolen Krishna Rajahrathanum; Permaul, Kugen; Govender, Algasan; Puri, Adarsh Kumar
Zygomycetes are known for their relatively high chitosan content (approximately 10% m/m) in comparison with other fungal genera. In this study, Mucor circinelloides was grown on the following industrial waste substrates: corn steep liquor (CSL); soft drink overflow spillage waste (DBW); and sugarcane molasses (MOL). Biomass production on waste substrates was statistically optimized by Plackett-Burman design in conjunction with Response Surface Methodology, followed by validation of the model. DBW hindered fungal biomass growth and was found to be a statistically insignificant variable and therefore omitted from further optimizations. The validated model produced a biomass of 77.87 g/L, a 2.65-fold increase over the highest-yielding unoptimized medium. Fungal biomass obtained after batch fermentation was subjected to acid-alkaline treatment for chitin extraction from the cell wall and deacetylation of the chitin to chitosan. A yield of 8-9% chitosan was obtained from the fungal biomass. FTIR spectroscopic analysis was conducted on the extracted fungal chitosan to compare extracted chitosan against commercial chitosan and chitosan monomer. The waste-grown, fungal-derived chitosan profiles were similar to those of commercial crustacean chitosan. The extracted chitosan was used in conjunction with additives and solvent systems to create biopolymer variants with differing properties. A library of data from the chitosan biopolymer variants was generated with considerable differences in characteristics based on their composition. Improvements in sample #11 (the most modified formulation) in contrast to the most common chitosan biopolymer film composition used in literature (sample #9), included a 3.37-fold improvement in the static force required to break the film. There was a 3.39-fold increase in tensile strength and an 11-fold reduction in elongation (%) and elongation rates. The creation of these variants will allow the use of these chitosan biopolymers for specific industrial applications.
Efficacy and mechanisms of antiretroviral drugs removal by algaefrom wastewater treatment plants
(2024-05) Reddy, Karen; Bux, Faizal; Kuttan Pillai, Sheena Kumari; Renuka, Nirmal; Moodley, Brenda
The presence, risks, and fate of pharmaceutical pollutants in the environment have raised concerns worldwide. South Africa, with the largest population consuming antiretroviral (ARV) drugs in Africa, faces challenges in efficiently removing these compounds from water bodies. This study's primary focus was to investigate the efficiency and mechanisms of nevirapine (NVP) removal by algae isolated from wastewater treatment processes. It included the isolation and screening of algal strains from wastewater treatment plants for their potential to remove ARV drugs, optimizing culture conditions to enhance removal efficiency, determining the potential mechanisms employed by selected algal strains for NVP remediation, and assessing the associated metabolic responses of algal cells to NVP using gene expression and metabolomics analyses. Eleven green indigenous fresh water microalgal isolates were screened from wastewater treatment plants (WWTPs) in KwaZulu-Natal, resulting in the selection of two strains, Coelastrella tenuitheca and Tetradesmus obliquus, based on their growth rates, biomass productivity and toxicity tolerance. In the ecotoxicity study, the calculated IC50 values of NVP (0–100 mg L−1) on selected algal strains after 96 h of exposure were 23.45 mg L−1 (C. tenuitheca) and 18.20 mg L−1 (T. obliquus), which far exceeds the concentration of NVP found in wastewater. Hence, T. obliquus and C. tenuitheca was selected for further NVP remediation studies using different cultivation conditions. A concentration range of 0-4000 ng L-1 of NVP was tested to assess the potential for NVP removal by both microalgae (autotrophic cultivation). Lower concentrations of NVP (up to 200 ng L−1) have shown to have a positive impact on microalgae growth. Specifically, in T. obliquus, the highest dry cell weight of 941.27 mg L−1 was obtained when exposed to a NVP concentration of 50 ng L−1. Both microalgae showed varying removal efficiencies (19.53–74.56%) when exposed to different NVP concentrations. During the late log phase on day 8, T. obliquus achieved the highest NVP removal efficiency, removing 74.56% of the NVP, while C. tenuitheca achieved a removal rate of 48% at an NVP concentration of 50 ng L−1. The photosynthetic efficiency (Fv/Fm and rETR) of both microalgal species was found to be unaffected by environmental concentrations of NVP (up to 4000 ng L−1) during the mid-log phase of growth. Furthermore, the scanning electron microscopy (SEM) analysis demonstrated that both algal species produced distinct ridges on their cell surfaces after NVP uptake. Additional evaluations were conducted on the microalga, T. obliquus, for the removal of NVP at 4000 ng L-1, as well as their cellular response (expression of antioxidant enzymes and metabolomics) and biomass production under different cultivation modes (autotrophic, heterotrophic, and mixotrophic). The highest NVP removal efficiency was observed under mixotrophic (80.13%) growth on day 8, whilst heterotrophic and autotrophic cultivation modes removed 70.30% and 64.40%, respectively. Mass balance calculations showed that the primary removal mechanism was identified as biodegradation, with a relatively low contribution from bioadsorption (2.39-3.36%) and bioaccumulation (0.55- 0.87%). Fourier-transform infrared (FTIR) spectroscopy results of harvested microalgal cells displayed bands in the region of 950-1000 cm-1, indicating the presence of aromatic C-H rings found in NVP. Additionally, 6 possible biotransformation products of NVP were identified by untargeted liquid chromatography-time of flight mass spectrometry. Additionally, under autotrophic conditions, the gene expression analysis revealed heightened activities of superoxide dismutase (sod1), glutathione peroxidase (gpx1) and catalase (cat2) in T. obliquus. The upregulation of antioxidant genes enhances the organism's ability to defend against oxidative stress induced by NVP. The expression levels of antioxidant genes were significantly reduced during heterotrophic and mixotrophic growth, suggesting microalgae can overcome oxidative stress with glucose supplementation. To further investigate the cellular level response of microalgal cells to NVP, metabolomic analysis was carried to out to identify and quantify key algal metabolites during mixotrophic cultivation. The increase in activity of the fatty acid biosynthesis pathway and carbohydrate synthesis was observed by T. obliquus in the presence of NVP under mixotrophic growth conditions. The findings from this study emphasize the significant potential of microalgae in the field of ARV drug remediation.

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