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Research Publications (Applied Sciences)

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

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    Physico-chemical and biotic factors influencing microalgal seed culture propagation for inoculation of a large scale raceway pond
    (African Journals Online, 2014) Mutanda, Taurai; Ranjith Kumar, R.; Bux, Faizal
    The growth of Chlorella vulgaris in open pond aquatic conditions poses serious challenges due to the interplay of both physico-chemical and biotic factors. We report here the monitoring of physico-chemical and biotic parameters affecting the propagation of C. vulgaris seed culture for inoculation of a large scale raceway pond (300 000 L capacity) in South Africa. The C. vulgarisstrain used for this purpose was isolated from a wastewater maturation pond and characterized for its potential for biomass and lipid production. The isolate was grown aseptically in 4 × 25 L aspirator bottles in BG-11 medium under ambient laboratory conditions and the culture was supplied with filtered air and exposed to 200 µmol photons per m2 per second using Gro-Lux agricultural fluorescent lights. The culture was transferred to a 500 L capacity portable pool under open conditions. This pond was used to further inoculate 3 more portable ponds. Physico-chemical and biotic growth parameters were monitored on a daily basis in the three ponds. The over reliance on fossil fuels will have a major impact on power supply in the near future if renewable sources of energy are not developed at a fast pace. The developed inoculum was subsequently used to inoculate an open raceway pond for large scale biomass production for biodiesel production.
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    Artificial intelligence for the evaluation of operational parameters influencing Nitrification and Nitrifiers in an activated sludge process
    (Springer Science+Business Media, 2016) Awolusi, Oluyemi Olatunji; Nasr, Mahmoud; Kumari, Sheena K.; Bux, Faizal
    Abstract Nitrification at a full-scale activated sludge plant treating municipal wastewater was monitored over a period of 237 days. A combination of fluorescent in situ hybridiza-tion (FISH) and quantitative real-time polymerase chain reac-tion (qPCR) were used for identifying and quantifying the dominant nitrifiers in the plant. Adaptive neuro-fuzzy infer-ence system (ANFIS), Pearson’s correlation coefficient, and quadratic models were employed in evaluating the plant oper-ational conditions that influence the nitrification performance. The ammonia-oxidizing bacteria (AOB) abundance was with-in the range of 1.55 × 108–1.65 × 1010 copies L−1, while Nitrobacter spp. and Nitrospira spp. were 9.32 × 109–1.40 × 1011 copies L− 1 and 2.39 × 109 –3.76 × 1010 copies L−1, respectively. Specific nitrification rate (qN)was significantly affected by temperature (r 0.726, p 0.002), hy-draulic retention time (HRT) (r −0.651, p 0.009), and ammo-nia loading rate (ALR) (r 0.571, p 0.026). Additionally, AOB was considerably influenced by HRT (r −0.741, p 0.002) and temperature (r 0.517, p 0.048), while HRT negatively impact-ed Nitrospira spp. (r −0.627, p 0.012). A quadratic combina-tion of HRT and food-to-microorganism (F/M) ratio also im-pacted qN (r2 0.50), AOB (r2 0.61), and Nitrospira spp. (r2 0.72), while Nitrobacter spp. was considerably influenced by a polynomial function of F/M ratio and temperature (r2 0.49). The study demonstrated that ANFIS could be used as a tool to describe the factors influencing nitrification process at full-scale wastewater treatment plants.
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    A low cost one pot synthesis of biodiesel from waste frying oil (WFO) using a novel material, b-potassium dizirconate (b-K2Zr2O5)
    (Elsevier, 2016) Singh, Veena; Bux, Faizal; Sharma, Yogesh Chandra
    Biodiesel was synthesized from waste frying oil (WFO) using b-potassium dizirconate (b-K2Zr2O5)asa novel heterogeneous catalyst. Synthesized catalyst was characterized by X-ray diffractometry (XRD), thermogravimetric analysis (TGA), attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), particle size analyser, scanning electron microscopy (SEM), BET surface area and basicity. Various reaction conditions such as molar ratio of methanol: oil, catalyst amount (wt%), reaction temperature, time and reusability of catalyst were studied for transesterification reaction with the catalyst, b-K2Zr2O5. High biodiesel conversion of 96.85% was observed at a 10:1 M ratio (alcohol: oil), 4 wt% catalyst at 65 C for 2 h. WFO was characterized by GCMS and biodiesel conversion was ascertained by Fourier transform nuclear magnetic resonance (1H and 13C FTNMR) spectroscopy. It was first time that b-potassium dizirconate was used as a catalyst for biodiesel synthesis. The catalyst was reused up to five times without significant loss in its activity. Physical and chemical properties of FAME such as flash point, fire point, cloud point, density, and kinematic viscosity were deliberated.
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    Trends and novel strategies for enhancing lipid accumulation and quality in microalgae
    (Elsevier, 2016) Singh, Poonam; Kumari, Sheena K.; Guldhe, Abhishek; Rawat, Ismail; Misra, Rohit; Bux, Faizal
    In order to realize the potential of microalgal biodiesel there is a need for substantial impetus involving interventions to radically improve lipid yields upstream. Nutrient stress and alteration to cultivation conditions are commonly used lipid enhancement strategies in microalgae. The main bottleneck of applying conventional strategies is their scalability as some of these strategies incur additional cost and energy. Novel lipid enhancement strategies have emerged to research forefront to overcome these challenges. In this review, the latest trends in microalgal lipid enhancement strategies, possible solutions and future directions are critically discussed. Advanced strategies such as combined nutrient and culti-vation condition stress, microalgae–bacteria interactions, use of phytohormones EDTA and chemical additives, improving light conditions using LED, dyes and paints, and gene expression analysis are described. Molecular approaches such as metabolic and genetic engineering are emerging as the potential lipid enhancing strategies. Recent advancements in gene expression studies, genetic and metabolic engineering have shown promising results in enhancing lipid productivity in microalgae; however environmental risk and long term viability are still major challenges.
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    Biodiesel from microalgae: A critical evaluation from laboratory to large scale production
    (Elsevier, 2013) Rawat, Ismail; Ranjith Kumar, R.; Mutanda, Taurai; Bux, Faizal
    The economically significant production of carbon-neutral biodiesel from microalgae has been hailed as the ultimate alternative to depleting resources of petro-diesel due to its high cellular concentration of lip-ids, resources and economic sustainability and overall potential advantages over other sources of biofu-els. Pertinent questions however need to be answered on the commercial viability of large scale production of biodiesel from microalgae. Vital steps need to be critically analysed at each stage. Isolation of microalgae should be based on the question of whether marine or freshwater microalgae, cultures from collections or indigenous wild types are best suited for large scale production. Furthermore, the determination of initial sampling points play a pivotal role in the determination of strain selection as well as strain viability. The screening process should identify, purify and select lipid producing strains. Are natural strains or stressed strains higher in lipid productivity? The synergistic interactions that occur nat-urally between algae and other microorganisms cannot be ignored. A lot of literature is available on the downstream processing of microalgae but a few reports are available on the upstream processing of mic-roalgae for biomass and lipid production for biodiesel production. We present in this review an empirical and critical analysis on the potential of translating research findings from laboratory scale trials to full scale application. The move from laboratory to large scale microalgal cultivation requires careful plan-ning. It is imperative to do extensive pre-pilot demonstration trials and formulate a suitable trajectory for possible data extrapolation for large scale experimental designs. The pros and cons of the two widely used methods for growing microalgae by photobioreactors or open raceway ponds are discussed in detail. In addition, current methods for biomass harvesting and lipid extraction are critically evaluated. This would be novel approach to economical biodiesel production from microalgae in the near future. Glob-ally, microalgae are largest biomass producers having higher neutral lipid content outcompeting terres-trial plants for biofuel production. However, the viscosities of microalgal oils are usually higher than that of petroleum diesel.
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    An evaluation of the efficacy of using selected solvents for the extraction of lipids from algal biomass by the soxhlet extraction method
    (Elsevier, 2013-08-14) Ramluckan, Krishan; Bux, Faizal; Moodley, Kandasamy G.
    The use of solvents for the extraction of lipids from algal biomass has been a method of choice for many years. The soxhlet extraction method was chosen because of its simplicity in operation, relative safety and potential for upscaling to industrial plant level. The source of algal biomass was a raceway pond. Chlorella sp. which is known to produce larger amounts of oil than other indigenous species was used for this investigation. Thirteen solvents spanning a range of polarities and solubilities were selected for this study. Extraction methodology involved the use of single solvents, selected binary solvent mixtures and time-based extractions which were varied from 1 to 5 h. Ultraviolet (UV) spectroscopy was used to determine chlorophyll content of the lipid extracts and gas chromatography was used for the identifica-tion and quantitation of the lipids. Analysis showed that ethanol, chloroform and hexane were generally more efficient in the extraction of lipids than the other solvents studied, producing lipid contents in excess of 10%. The time-based trials indicated that the optimum extraction time was 3 h for the solvents selected. The binary solvent mixture with the greatest extraction efficiency (i.e. >10% lipid extract) was obtained with the 1:1 mixture of chloroform:ethanol. Chlorophyll quantities varied for each solvent extract with chloroform and methanol producing the highest values at >1%. Chromatography was effec-tive in identifying lipids used in the production of biodiesel.