Research Publications (Applied Sciences)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/213

Browse

Now showing 1 - 8 of 8

Biodiesel synthesis from microalgae using immobilized Aspergillus niger whole cell lipase biocatalyst
(Elsevier, 2016) Guldhe, Abhishek; Singh, Poonam; Kumari, Sheena K.; Rawat, Ismail; Permaul, Kugen; Bux, Faizal
Whole cell lipase catalysis and microalgal feedstocks make overall biodiesel synthesis greener and sustainable. In this study, a novel approach of whole cell lipase-catalyzed conversion of Scenedesmus obliquus lipids was investigated for biodiesel synthesis. Microalgal biodiesel was characterized for its fuel properties. Optimization of process parameters for immobilized Aspergillus niger whole cell lipase-catalyzed biodiesel synthesis was carried out. Highest biodiesel conversion of 53.76% was achieved from S. obliquus lipids at 35 °C, methanol to oil ratio of 5:1 and 2.5% water content based on oil weight with 6 BSPs (Biomass support particles). Step-wise methanol addition was applied to account for methanol tolerance, which improved biodiesel conversion upto 80.97% and gave 90.82 ± 1.43% yield. Immobilized A. niger lipase can be used for 2 batches without signiﬁcant loss in conversion efﬁciency. Most of the fuel properties of biodiesel met the speciﬁcations set by international standards.
Digitalization in developing maritime business environments towards ensuring sustainability
(MDPI, 2020-11-06) Kapidani, Nexhat; Bauk, Sanja; Davidson, Innocent E.
The paper focuses on assessing the level of digitalization in several developing maritime business environments in Albania, Bosnia and Herzegovina, Montenegro, and Serbia. The assessment has been done in reference to Holtham’s and Courtney’s Intelligent Information and Communication Technologies (ICT) Exploiter Model. The dimensions as maritime business system effectiveness, roles, and skills of information technology personnel, ladders of knowledge, ICT strategy, organizational culture, and manager’s mindset are analyzed. In addition, benchmarking with findings from developed maritime business environments in Croatia, Greece, Italy, and Slovenia, which belong to the European Union (EU), by using the same model, has been conducted. This is done with the aim to outline directions for improving the quality and speed of digitalization in non-EU countries, which have been functioning for decades in transitional conditions. The maritime ecosystem naturally has a tendency to be unique and to function smoothly as such. Alleviating the differences in the level and effectiveness of digitalization in developed and developing European countries is a path towards achieving this goal. By sharing their own expertise in the rational and intelligent use of ICT, developed EU countries can support developing non-EU countries towards ensuring sustainability in the entire European and worldwide maritime business ecosystem.
Engineering of small laccase (SLAC) from Streptomyces coelicolor for application in biocatalysis and surface functionalisation
(2020) Yadav, Deepti; Kudanga, Tukayi; Mchunu, Nokuthula Peace; Le Roes-Hill, Marilize
The small laccase (SLAC) from Streptomyces coelicolor A3(2) is a versatile and industrially relevant biocatalyst mainly because of desirable characteristics such as activity at high temperatures and alkaline pH and relative stability against common laccase inhibitors. However, low yield from natural hosts, low catalytic efficiency and lack of reusability are some of the technological barriers that tend to limit the industrial application of the SLAC. In the present study, strategies have been developed to engineer SLAC for the improvement of catalytic properties and expression of SLAC for potential application in biocatalysis and surface functionalisation. Site directed mutagenesis was used to enhance properties of the enzyme. Four mutant sites (Y229A, Y230A, V290N and M198G) were selected on the basis of some positive results from literature and from the four sites, ten composite mutants including double, triple and quadruple mutants were generated. The produced variant SLAC enzymes were purified to homogeneity by Ni2+ affinity chromatography in a single step. A double mutant (Y230A/V290N) showed a low Km value which was 75% lower than wild type small laccase (WT-SLAC). Double mutations (Y230A/V290N and Y229A/M198G) enhanced the ability of the enzyme to decolourise common industrial dyes. For example, the double mutant Y229A/M198G exhibited a 1.2-fold higher catalytic efficiency (9.12 min-1mM-1) for the oxidation of ABTS than the WT-SLAC (7.46 min-1mM-1) and was able to decolourise 50 mg/L of Methyl Red (MR) completely, whilst only 28% decolourisation was observed with the WT-SLAC. To enhance enzyme production, the SLAC (from S. coelicolor A3(2)) was expressed in the methylotrophic yeast Pichia pastoris. The SLAC gene was cloned under the control of methanol inducible alcohol oxidase 1 (AOX1) promoter. The recombinant P. pastoris yielded high titres of extracellular laccase (500 ± 10 U/L) upon induction with methanol. The extracellular SLAC (~38 kDa) was purified to homogeneity with a specific activity of 8916.66 U/mg. The purified SLAC had an optimum activity at 80 C, but optimum pH varied with substrate used (pH 4 for ABTS and pH 8 for syringaldazine (SGZ) and 2,6-dimethoxy-phenol (2,6-DMP). Km values for ABTS, SGZ and 2,6-DMP were 142.85 μM, 10 μM and 54.55 μM and the corresponding kcat values were 60.6 s−1 , 25.36 s−1 and 27.84 s−1 , respectively. The t1/2 values of the recombinant SLAC (rSLAC) at 60 ºC, 70 ºC, 80 ºC were found to be 60 h, 32 h and 10 h, respectively. The enzyme deactivation energy (Ed) was 117.275 kJ/mol while ∆G, ∆H and ∆S for thermal inactivation of the rSLAC were all positive. To further enhance enzyme production, a dual promoter system was investigated using a combination of AOX (inducible promoter) and GAP (constitutive promoter). To this end, a recombinant P. pastoris strain harbouring rSLAC under control of both AOX and GAP promoters, was generated. A production level of 1800 U/L was recorded for rSLAC-GAPAOX which was about 3.6-fold higher than the single promoter system (rSLAC-AOX). Mixed feed strategy (9:1 ratio of methanol/glycerol) led to a positive influence in biomass accumulation and 1.5-fold increase in rSLAC expression, compared with induction of the double promoter system with methanol alone. To facilitate reusability of SLAC, the enzyme was immobilised onto surface of silanized magnetic nanoparticles (Si-MNP’s). Briefly, a silane layer was coated using 3-(aminopropyl) triethoxysilane (APTES) over the surface of MNPs, which was followed by immobilisation of rSLAC via covalent attachment. Field emission-scanning electron microscopy (FE-SEM) images of MNPs revealed that the diameter of the MNPs was in the range of 50-200 nm. Fourier transform-infrared spectroscopy (FT-IR) spectra of MNP, MNP/APTES and MNP/APTES/rSLAC, confirmed the presence of characteristic peaks at 589 cm-1, 2360 cm-1 and 1648 cm-1, respectively. MNP-rSLAC showed remarkable storage stability (retained ≥95% of initial activity after storage in Tris-HCl buffer 20 mM, pH 8 at 4 °C over a period of 30 days), temperature stability, and tolerance towards organic solvents and heavy metals. Repeated usage of MNP-rSLAC showed >73% of its initial activity after 10 catalytic cycles and the enzyme was easily recovered from the reaction mixture by the application of a magnetic field. The potential application of rSLAC was investigated in the degradation of several pollutants and in surface functionalisation. rSLAC efficiently decolourised two synthetic dyes tested belonging to triphenylmethane and azo group of dyes. More than 90% decolourisation was achieved for Brilliant Blue G and Trypan Blue in 6 hours without the assistance of any mediator. Several phenolic pollutants such as phenol, 4-chlorophenol (4-CP) and 4- fluorophenol (4-FP), categorised as “priority pollutants”, were completely degraded within 2 hours using only 2 U of rSLAC. Growth inhibition studies using Escherichia coli showed that rSLAC-mediated treatment of phenolic compounds reduced the toxicity of phenol, 4-CP and 4-FP by 90, 60 and 55%, respectively. In addition, ciprofloxacin and tetracycline, two of the most persistent classes of drugs were also degraded by rSLAC in combination with acetosyringone (AS) as mediator. rSLAC-AS degraded 95% of 5 mg/L ciprofloxacin (CIP) and 100 % of 150 mg/L of tetracycline (TC) within 6 hours. The removal of TC resulted in complete elimination of antibacterial activity while up to 48% reduction in antibacterial activity was observed when CIP was removed. The rSLAC also catalysed the functionalisation of two biological materials (chitosan and coconut fibres) to improve antimicrobial properties. The rSLAC oxidised functional molecules to corresponding radicals which reacted with the lignin moieties and amino groups of the coconut fibres and chitosan, respectively. The appearance of broad absorption band around 380 and 450 nm of the UV/Vis spectra of grafted chitosan films, indicated a reaction between oquinone and amino groups of chitosan. FT-IR spectrum of grafted biomaterials showed new aromatic skeletal vibrations as well as phenolic absorption bands indicating conjugation of allelochemicals onto chitosan and coconut fibres. Antimicrobial activities of grafted biomaterials were found to be up to 60% higher than that of their ungrafted counterparts. In conclusion, the SLAC from S. coelicolor A3(2) was engineered to enhance its catalytic properties and expressed extracellularly in P. pastoris. With combined use of constitutive and inducible promoters, production level reached up to 1800 U/L, which was among the highest yields attained for recombinant bacterial laccases expressed in P. pastoris. This study has shown that a combination of site-directed mutagenesis, secretory expression and immobilisation could lead to the production of a viable rSLAC for application in bioremediation and surface functionalisation.
Exploring strategies in mathematical proficiency in social sciences research
(Global Academy of Training and Research (GATR) Enterprise, 2022-12-31) Brijlall, Deonarain; Jimmy Ivasen, Selvam
Objective - This paper explores the mathematical proficiency espoused by Kilpatrick et al. to improve teacher and learner mathematics performance in South Africa. A mixed-method approach involving interviews and questionnaires was used. Methodology/Technique - The sample included 7 principals or deputy principals, 7 departmental heads who supervised mathematics, 1 mathematics teacher who taught mathematics in grades 10 to 12, 1 mathematics teacher who taught Mathematics, and 1 learner from each grade 8 to 12 was included in the sample. Each participant was interviewed and had to complete a questionnaire. Finding - Kilpatrick et al. (Kilpatrick, Swafford, & Findell, 2001), who viewed Mathematical Proficiency as a five-stranded process involving conceptual understanding, productive disposition, procedural fluency, strategic competence, and adaptive reasoning, were used as a lens through which this study was conducted. We discovered several systemic, societal, and pedagogical challenges that teachers and students faced, all of which had an impact on their Mathematics teaching and learning. Our findings were in line with what was found in the literature review. The researchers concluded that there were always intervention strategies that could help to reduce or eliminate the challenges that Mathematics teachers and students face. Novelty - The researchers concluded there were always intervention strategies that could assist in minimizing or eradicating the challenges faced by the teachers and learners of mathematics, thus improving their socio-economic standing. Type of Paper - Review Keywords: Conceptual Development, Mathematical Proficiency, Code-switching. JEL Classification: Z10 A14, 19. to this paper should be referred to as follows: Brijlall, D; Ivasen, S.J. (2022). Exploring strategies in mathematical proficiency in social sciences research, GATR-Global J. Bus. Soc. Sci. Review, 10(4), 249–266. https://doi.org/10.35609/gjbssr.2022.10.4(4)
Impact of Building and Refrigeration System’s Parameters on Energy Consumption in the Potato Cold Storage
(The Canadian Center of Science and Education, 2014) Singh, Ramkishore; Lazarus, Ian Joseph; Singh, S. P.
Cold storage is a key element for long term preservation and distribution of perishable items. A large quantity of perishable items is gone wastage every year due to inadequate storage facility in the countries like India. Their energy extensive refrigeration process makes them accountable for substantial share of total energy consumption in the country. Moreover, energy inefficiency in operation and building designs in the existing cold storages inhibits expansion of desirable storage facility. This study aims to explore the building and refrigeration system’s parameters that may influence the overall energy consumption in the storage. A survey was conducted in ten Indian potato cold storages and detail data of their energy consumption, building construction and refrigeration systems was collected. The collected data was analyzed quantitatively and qualitatively. Trend analysis technique was also used to establish relationship between specific energy consumption and identified parameters. Results show that the utilization factor has major impact on the energy consumption in the storages and the existing cold storages are not utilizing their storage capacities fully. Comparatively higher energy consumption was observed in the cold storages that have low utilization factors. Building aspect ratios and effective U-value of the building envelop were also identified one of the crucial parameters that can play a major role to improve the energy performance of the cold storages. As expected, a negligible variation in the specific energy consumption of the storages with the specific installed refrigeration systems and AHUs was observed.
Impact of challenges experienced by teachers and learners on mathematics performance in relation to their socio-economic standing
(Global Academy of Training and Research (GATR) Enterprise, 2022-09-25) Brijlall, Deonarain; Ivasen, Selvam Jimmy
Objective – This paper explores the challenges experienced by mathematics teachers and learners of seven high schools in South Africa. A mixed method approach involving interviews and questionnaires was used. Methodology – The sample included 7 principals or deputy principals, 7 departmental heads who supervised mathematics, 1 mathematics teacher who taught mathematics in grades 10 to 12, and 1 mathematics teacher who taught Mathematics in grades 8 and 9. In addition, 1 learner from each grade 8 to 12 was included in the sample. Each participant was interviewed using a structured interview schedule, followed by participants completing a questionnaire. Findings – Vygotsky's socio-cultural and conceptual development theories in mathematics education formed the basis of this study. The 'Inputs, Processes and Output" model of Howie and Kilpatrick's model of the five strands of achieving 'mathematics proficiency was adopted. We identified many systemic, societal, and pedagogical challenges that teachers and learners experienced, which affected their mathematics teaching and learning. Our findings correlated with research in the literature review. Novelty – The researchers concluded there were always intervention strategies that could assist in minimizing or eradicating the challenges faced by the teachers and learners of mathematics, thus improving their socio-economic standing. Type of Paper: Review JEL Classification: A14, 19. Keywords: Challenges, Strategies, Blended Learning, Scaffolding, Conceptual Development, Collaborative Learning. Reference to this paper should be made as follows: Brijlall, D; Ivasen, S.J. (2022). The impact of challenges experienced by teachers and learners on Mathematics performance, in relation to their socio-economic standing, J. Bus. Econ. Review, 7(2), 112–126. https://doi.org/10.35609/jber.2022.7.2(1)
Matching interaction design principles and integrated navigation systems in an electronic classroom
(Faculty of Maritime Studies Split, 2020-04) Bauk, Sanja; Fajardo-Flores, Silvia
This article deals with cross-cultural and cross-disciplinary virtual engagement aimed to match human-computer interaction design principles and contemporary integrated navigation information systems. As interaction design principles ten general principles - heuristics are used, and as examples of contemporary navigation information systems, chart Radio Detection (or Direction) and Ranging (RADAR) device and Electronic Chart Display and Information System (ECDIS) are used. This cross-disciplinary research has been achieved through a Collaborative Online International Learning (COIL) project by Durban University of Technology (DUT) in South Africa and University of Colima (UoC) in Mexico. Namely, the students from both sides guided by their lecturers have been engaged in analyzing today’s most frequently used marine navigational aids from the perspective of their reliability and user centeredness. The complexity of the systems and the lack of standards are observed as main problems when it comes to marine information systems effectiveness and their user centeredness.
The prevalence of selected emerging pathogenic species in wastewater and receiving water bodies
(2022-03-16) Govender, Reshme; Stenström, Thor Axel; Pillai, Santhosh Kumar Kuttan; Swalaha, Feroz Mahomed; Bux, Faizal
Antibiotic resistance is one of the biggest threats to global health, due to the excessive use of antibiotics, among other factors. Aquatic environments are considered hotspots for antibiotic-resistant bacteria and genes due to pollution caused by various anthropogenic activities. In this study, four emerging opportunistic pathogens viz., Acinetobacter spp., Pseudomonas spp., Aeromonas spp., and Stenotrophomonas maltophilia were investigated to understand their distribution, source, and resistance patterns in wastewater and surface water. Among these, Acinetobacter baumannii and Pseudomonas aeruginosa have been listed by the World Health Organization (WHO) in 2017 as priority bacteria for further research and development. This study focused on the Umhlangane River, located in the north of Durban, in KwaZulu Natal, South Africa. The possible effect of anthropogenic activities such as discharges from wastewater treatment plants (WWTPs), hospitals, informal settlements, and veterinary clinics on the occurrence of antibiotic-resistance, and virulence signatures of the targeted organisms, was investigated. Sixty samples (12 wastewater, 48 surface water) were collected monthly (November 2016 to April 2017). This included influent and effluent of a wastewater treatment plant (WWTP) and four additional sampling sites (upstream and downstream of the WWTP, a hospital, an informal settlement, and a veterinary clinic). In addition, to the sixty samples, further samplings of aquatic plants (n=16) and sediments (n=16) were done in October 2017, specifically for the isolation of Stenotrophomonas maltophilia. The isolation and enumeration were carried out on selective media for each bacterium. The PCR positive isolates were identified using Matrix-Assisted Laser Desorption Ionization -Time of Flight Mass Spectrometry (MALDI-TOF MS) and 16S rRNA sequencing. In addition, advanced methods such as Flow Cytometry (FCM) and Droplet Digital PCR (ddPCR) were used to detect and quantify the bacteria, in comparison to conventional methods. The multiple antibiotic resistance (MAR) index was calculated to ascertain the contribution of these pollution sources to the proliferation of antibiotic-resistant bacteria in surface water. Varying counts (log10 CFU/mL) of Aeromonas spp. (2.5±0.8 to 3.3±0.4), Pseudomonas spp. (0.6±1.0 to 1.8±1.0) and Acinetobacter spp. (2.0±1.5 to 2.6±1.2) were obtained. S. maltophilia was found in the water column only at two sites and ranged from 2.7±0.3 to 4.1±1.0 log10 CFU/mL. However, it was found abundantly in the plant rhizosphere (3.6±0.1 to 4.2±0.6 log10 CFU/mL) and sediment (3.8±0.1 to 5.0±0.1 log10 CFU/mL) samples. The major Aeromonas species identified by MALDI-TOF MS was A. hydrophila / caviae (58%) whilst P. putida (51%) was common amongst the Pseudomonas isolates. The Acinetobacter genus was dominated by the Acinetobacter baumannii complex (26%), in contrast, all Stenotrophomonas maltophilia identities were confirmed via Polymerase Chain Reaction (PCR) and MALDI-TOF MS. Aeromonas (71%) and Pseudomonas (94%) isolates displayed resistance to three or more antibiotics. Aeromonas isolates displayed high resistance against ampicillin and had higher MAR indices, downstream of the hospital. The virulence gene, aer in Aeromonas was positively associated with the antibiotic resistance gene blaOXA (χ 2=6.657, p<0.05) and the antibiotic ceftazidime (χ 2=7.537, p<0.05). Pseudomonas exhibited high resistance against third-generation cephalosporins in comparison to carbapenems. Some Pseudomonas and Aeromonas isolates were extended-spectrum β-lactamase producing bacteria as the blaTEM gene was detected in Aeromonas spp. (33%) and Pseudomonas spp. (22%). All S. maltophilia isolates were resistant to the antibiotic’s trimethoprim-sulphamethoxazole, meropenem, imipenem, ampicillin, and cefixime. Acinetobacter isolates were resistant to trimethoprimsulphamethoxazole (96%) and polymyxin (86%). The genes coding for resistance against these antibiotics were detected in both S. maltophilia and Acinetobacter. Efflux pump genes were detected in all isolates of S. maltophilia. High MAR indices were observed in isolates of Pseudomonas, S. maltophilia, and Acinetobacter at the hospital site. However, Aeromonas spp. had the highest MAR in isolates from the WWTP effluents. A comparative analysis of three different methods was performed to understand their applicability and accuracy in detecting these pathogens from wastewater samples. The total viable count using the LIVE/DEAD Baclight bacterial viability kit measured an average count (log10 bacteria per mL) of 7.8±0.03 (influent) and 6.7±0.07 (effluent) using the Flow Cytometer. The total viable count using the BacLight kit was higher than the total plate count, which was 6.46±0.02 and 4.63±0.07 log10 CFU/mLfor influent and effluent, respectively. Similarly, the concentration for each of the target bacteria determined using Flow Cytometry combined with Fluorescent-In situ hybridization (Flow-FISH) method ranged from 5.41±0.07 to 5.92±0.02 (influent) and 3.43±0.2 to 4.31±0.15 (effluent) log10 bacteria per mL which was higher than the selective plate counts (3.81±0.35 to 4.17±0.1 and 3.16±0.17 to 3.7±0.20 log10 CFU/mL, for influent and effluent respectively). The ddPCR results obtained showed the highest concentration of bacteria from both influent and effluent samples in comparison to the Flow-FISH and the plate count methods, indicating the sensitivity of this method in detecting both live and dead cells. Pseudomonas was observed to be dominant and was found in the concentration of 7.19±0.24 copies per mL (influent) and 6.48±0.20 copies per mL (effluent) while S. maltophilia (influent: 5.4 ± 0.90 copies per mL effluent: 4.53±0.57 copies per mL) was detected in the lowest concentration. A similar trend was observed in comparison to the data from the plate counts, albeit at lower concentrations. This study, therefore, makes significant contributions in several areas; firstly, it shows the abundance of opportunistic, antibiotic-resistant, and virulent bacteria in wastewater and surface water within Durban. It further demonstrates that these bacteria are mainly from anthropogenic sources such as hospitals and WWTPs. Additionally, the findings indicate the potential for community-acquired infections with these bacteria, necessitating the need for risk reduction interventions aimed at reducing environmental pollution and exposure.