Faculty of Applied Sciences
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Item Investigation of combined effect of nitrogen, phosphorus and iron on lipid productivity of microalgae Ankistrodesmus falcatus KJ671624 using response surface methodology(Elsevier, 2015-02-15) Singh, Poonam; Guldhe, Abhishek; Kumari, Sheena K.; Rawat, Ismail; Bux, FaizalEnhancement of lipid accumulation is essential to improve the commercial feasibility of microalgal biodiesel production. An oleaginous microalgal strain, Ankistrodesmus falcatus KJ671624 was evaluated for its potential as a biodiesel feedstock in this study. The collective effect of nutrient (nitrogen, phospho-rous and iron) stresses on the lipid productivity of the selected strain was studied by response surface methodology. The highest lipid content of 59.6% and lipid productivity of 74.07 mg L−1 d−1 was obtained under nutrient stress with nitrogen 750 mg L−1, phosphorus 0 mg L−1 and iron 9 mg L−1. The photosyn-thetic behaviour validates the high lipid productivity under combined nutrient stress condition. Saturated fatty acid composition was increased by 38.49% under selected nutrient stress condition compared to BG11 medium. The enhanced lipid accumulation with suitable lipid profile (C16:0, C18:1, C18:2, C18:3) and biodiesel conversion of 91.54 ± 1.43% achieved in A. falcatus KJ671624 further confirm its potential as a promising feedstock for biodiesel production.Item 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, FaizalIn 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.Item 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, FaizalWhole 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.Item Biocatalytic conversion of lipids from microalgae Scenedesmus obliquus to biodiesel using Pseudomonas fluorescens lipase(Elsevier, 2015-01-31) Guldhe, Abhishek; Singh, Bhaskar; Rawat, Ismail; Perumal, Kugen; Bux, FaizalConversion of microalgal lipids using biocatalyst is a novel and greener approach to produce biodiesel. Free and immobilized lipases from Candida sp. and Pseudomonas fluorescens along with free lipases from porcine pancreas and wheat germ were screened for biodiesel conversion of Scenedesmus obliquus lipids. Among selected lipases from various sources immobilized lipase from P. fluorescens showed superior biodiesel conversion. Optimization of reaction parameters viz. lipase amount, temperature, methanol to oil molar ratio and water content was carried out using response surface methodology. Best conversion of 66.55% was achieved at 35 °C, methanol to oil ratio of 3:1 with 10% enzyme amount and 2.5% water content based on oil weight. To tackle methanol tolerance step-wise methanol addition was applied, which improved biodiesel conversion upto 90.81%. Immobilized P. fluorescens lipase can be used for 4 batches without much loss in conversion efficiency (>95%). Biodiesel produced has the cetane number of 51.77, Calorific value of 37.67 MJ kg−1. Most of the fuel properties of biodiesel met the specifications set by ASTM and EN standards.Item Biodiesel from microalgae: A critical evaluation from laboratory to large scale production(Elsevier, 2013) Rawat, Ismail; Ranjith Kumar, R.; Mutanda, Taurai; Bux, FaizalThe 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.