• Energy Research

Enhanced biofuel production strategies from microalgae by employing affordable bio-waste usage are fetching significance, nowadays. This study examines the effect of VWE for enhanced biomass from new indigenous microalgal isolates, Asterarcys sp. SPC, Scenedesmus sp. KT-U, Scenedesmus sp. KTWL-A, Coelastrum sp. T-E, and Chlorella sp. TWL-B. The growth of microalgae in VWE-treated growth media showed considerable increase (1.14-2.3 folds) than control medium (without VWE). Further, two effective native microalgae were selected based on growth in VWE treatment, biomass productivity, and TAG accumulation through statistical clustering analysis. Mixotrophic batch cultivation of Scenedesmus sp. KT-U and Asterarcys sp. SPC cultivated using VWE treatment in the optimum concentration had produced significant average increase in BP (1.8 and 1.4 folds, respectively) than control (without VWE). Whereas in the lipid production phase, there was a noticeable increase in lipid yield in VWE-treated cells of lipid phase (231.8 ± 17.9 mg/L and 243.5 ± 25 mg/L) in Scenedesmus sp. KT-U and Asterarcys sp. SPC, respectively, than in control (140.5 ± 28 mg/L and 166.4 ± 23 mg/L) with considerable TAG accumulation. Thus, this study imparts strain selection process of native microalgae based on vegetable waste usage for improved yield of biomass and lipid amenable for cost-effective biodiesel production.

Enhanced biofuel production strategies from microalgae by employing affordable bio-waste usage are fetching significance, nowadays. This study examines the effect of VWE for enhanced biomass from new indigenous microalgal isolates, Asterarcys sp. SPC, Scenedesmus sp. KT-U, Scenedesmus sp. KTWL-A, Coelastrum sp. T-E, and Chlorella sp. TWL-B. The growth of microalgae in VWE-treated growth media showed considerable increase (1.14-2.3 folds) than control medium (without VWE). Further, two effective native microalgae were selected based on growth in VWE treatment, biomass productivity, and TAG accumulation through statistical clustering analysis. Mixotrophic batch cultivation of Scenedesmus sp. KT-U and Asterarcys sp. SPC cultivated using VWE treatment in the optimum concentration had produced significant average increase in BP (1.8 and 1.4 folds, respectively) than control (without VWE). Whereas in the lipid production phase, there was a noticeable increase in lipid yield in VWE-treated cells of lipid phase (231.8 ± 17.9 mg/L and 243.5 ± 25 mg/L) in Scenedesmus sp. KT-U and Asterarcys sp. SPC, respectively, than in control (140.5 ± 28 mg/L and 166.4 ± 23 mg/L) with considerable TAG accumulation. Thus, this study imparts strain selection process of native microalgae based on vegetable waste usage for improved yield of biomass and lipid amenable for cost-effective biodiesel production.

In this study, two freshwater cyanobacteria, Oscillatoria sp. 50A and Synechocystis sp. NN have been evaluated for biodiesel production. Among the two cyanobacteria, Synechocystis sp. NN was isolated, identified by its 16S rRNA gene sequencing. Effects of sodium bicarbonate (SBC), tannery effluent (TE), coir pith (CP) and light stress (L1) on biomass and lipid production of Synechocystis sp. NN were studied. Result showed that maximum biomass productivity of 18.7 ± 0.9 mg/L/day (1.9 folds) was observed in TE supplemented BG-11 media than normal BG-11 media. Meantime, maximum lipid productivity of 2.6 ± 0.4 mg/L/day (1.4 folds) was observed in CP supplemented BG-11 media than normal media. Further, fatty acid composition analyses by GC–MS showed that C16, C18:1 in Oscillatoria sp. 50A and C16, C20:1, C22:1 in Synechocystis sp. NN were predominant and the fuel properties were also in accordance with the international standards. Besides gene expression of acetyl CoA carboxylase D of Synechocystis sp. NN, analyzed by RT-PCR revealed that transcripts of accD were up-regulated by 1.2–4.7 folds in different media conditions. The findings of this study showed that Synechocystis sp. NN can be utilized as a suitable feedstock that is amenable for cultivation using wastes as nutrient source.

In this study, two freshwater cyanobacteria, Oscillatoria sp. 50A and Synechocystis sp. NN have been evaluated for biodiesel production. Among the two cyanobacteria, Synechocystis sp. NN was isolated, identified by its 16S rRNA gene sequencing. Effects of sodium bicarbonate (SBC), tannery effluent (TE), coir pith (CP) and light stress (L1) on biomass and lipid production of Synechocystis sp. NN were studied. Result showed that maximum biomass productivity of 18.7 ± 0.9 mg/L/day (1.9 folds) was observed in TE supplemented BG-11 media than normal BG-11 media. Meantime, maximum lipid productivity of 2.6 ± 0.4 mg/L/day (1.4 folds) was observed in CP supplemented BG-11 media than normal media. Further, fatty acid composition analyses by GC–MS showed that C16, C18:1 in Oscillatoria sp. 50A and C16, C20:1, C22:1 in Synechocystis sp. NN were predominant and the fuel properties were also in accordance with the international standards. Besides gene expression of acetyl CoA carboxylase D of Synechocystis sp. NN, analyzed by RT-PCR revealed that transcripts of accD were up-regulated by 1.2–4.7 folds in different media conditions. The findings of this study showed that Synechocystis sp. NN can be utilized as a suitable feedstock that is amenable for cultivation using wastes as nutrient source.

A cheap cultivation of microalgae greatly reduces the biodiesel production cost. Subsequently in this study, citric acid and effluents from sugar and tannery industries were used as the nutritional supplements for the improvement of biomass and TAG production in Phaeodactylum tricornutum using two-step cultivation. When compared to control (media without supplementation), a considerable increase in biomass and chlorophyll a was obtained with citric acid (CA) and sugar industry effluent (SIE) supplemented media. In the two-step cultivation method, biomass raised from CA (100 mg·L-1) and SIE (1.5 mL·L-1) supplementations in the first step, viz. biomass production (BP) step was allowed for lipid accumulation in the second step, viz. lipid production (LP) step, and thus yielded enhanced lipids of 11.5 ± 0.7 mg·L-1·day-1 and 13.5 ± 1.9 mg·L-1·day-1 respectively, with improved TAG synthesis. Further, differential expression analysis of TAG biosynthetic genes of P. tricornutum under single-step and two-step cultivation modes were performed, and the gene expression patterns were studied.

A cheap cultivation of microalgae greatly reduces the biodiesel production cost. Subsequently in this study, citric acid and effluents from sugar and tannery industries were used as the nutritional supplements for the improvement of biomass and TAG production in Phaeodactylum tricornutum using two-step cultivation. When compared to control (media without supplementation), a considerable increase in biomass and chlorophyll a was obtained with citric acid (CA) and sugar industry effluent (SIE) supplemented media. In the two-step cultivation method, biomass raised from CA (100 mg·L-1) and SIE (1.5 mL·L-1) supplementations in the first step, viz. biomass production (BP) step was allowed for lipid accumulation in the second step, viz. lipid production (LP) step, and thus yielded enhanced lipids of 11.5 ± 0.7 mg·L-1·day-1 and 13.5 ± 1.9 mg·L-1·day-1 respectively, with improved TAG synthesis. Further, differential expression analysis of TAG biosynthetic genes of P. tricornutum under single-step and two-step cultivation modes were performed, and the gene expression patterns were studied.

Two fresh water microalgae, Coelastrella sp. M-60 and Micractinium sp. M-13 were investigated in this study for their potential of biodiesel production. For increasing biomass and lipid production, these microalgae were subjected to nutrient starvation (nitrogen, phosphorous, iron), salinity stress and nutrient supplementation with sugarcane industry effluent, citric acid, glucose and vitamin B12. The lipid productivity obtained from the isolates Coelastrella sp. M-60 (13.9 ± 0.4 mg/L/day) and Micractinium sp. M-13 (11.1 ± 0.2 mg/L/day) was maximum in salinity stress. The media supplemented with all the four nutrients yielded higher lipid productivity than the control. The response surface methodology (RSM) was employed to evaluate the effect of sugarcane industry effluent and citric acid on growth and lipid yield. Fatty acid profile of Coelastrella sp. M-60 and Micractinium sp. M-13 were composed of C-14, C-16:0, C-18:0, C-18:1 and C-18:2 and their fuel properties were also in accordance with international standards.

Two fresh water microalgae, Coelastrella sp. M-60 and Micractinium sp. M-13 were investigated in this study for their potential of biodiesel production. For increasing biomass and lipid production, these microalgae were subjected to nutrient starvation (nitrogen, phosphorous, iron), salinity stress and nutrient supplementation with sugarcane industry effluent, citric acid, glucose and vitamin B12. The lipid productivity obtained from the isolates Coelastrella sp. M-60 (13.9 ± 0.4 mg/L/day) and Micractinium sp. M-13 (11.1 ± 0.2 mg/L/day) was maximum in salinity stress. The media supplemented with all the four nutrients yielded higher lipid productivity than the control. The response surface methodology (RSM) was employed to evaluate the effect of sugarcane industry effluent and citric acid on growth and lipid yield. Fatty acid profile of Coelastrella sp. M-60 and Micractinium sp. M-13 were composed of C-14, C-16:0, C-18:0, C-18:1 and C-18:2 and their fuel properties were also in accordance with international standards.

Lipid from microalgae is one of the putative oil resources to facilitate the biodiesel production during this era of energy dissipation and environmental pollution. In this study, the key parameters such as biomass productivity, lipid productivity and lipid content were evaluated at the early stationary phase of Chlamydomonas reinhardtii, CC1010 cultivated in nutrient starved (nitrogen, phosphorous), glucose (0.05%, 0.1%, 0.15% and 0.2%) and vitamin B12 supplementation (0.001%, 0.002% and 0.003%) in Tris-Acetate-Phosphate (TAP) medium. The lipid content in nitrogen starved media was 61% which is 2.34 folds higher than nutrient sufficient TAP medium. Glucose supplementation has lead to proportional increase in biomass productivity with the increasing concentration of glucose whereas vitamin B12 supplementations had not shown any influence in lipid and biomass production. Further, fatty acid methyl ester (FAME) profiling of C. reinhardtii, CC 1010 has revealed more than 80% of total SFA (saturated fatty acid) and MUFA (mono unsaturated fatty acid) content. Quality checking parameters of biodiesel like cetane number, saponification value, iodine number and degree of unsaturation were analyzed and the biodiesel fuel properties were found to be appropriate as per the international standards, EN 14214 and ASTM D6751. Conclusively, among all the treatments, nitrogen starvation with 0.1% glucose supplementation had yielded high lipid content in C. reinhardtii, CC 1010.