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In this study, a freshwater microalga, Scenedesmus sp. SB1, was isolated, purified, and identified by its internal transcribed spacer region (ITS1-5.8S-ITS2). Media optimization through the Plackett–Burman Design and response surface methodology (RSM) showed a maximum exopolysaccharide (EPS) production of 48 mg/L (1.8-fold higher than that for unoptimized media). Characterization using gas chromatography–mass spectrometry, Fourier transform infrared, X-ray diffraction, and thermogravimetric analysis reveals that the EPS is a sulfated pectin polysaccharide with a crystallinity index of 15.2% and prompt thermal stability. Furthermore, the photoelectrogenic activity of Scenedesmus sp. SB1 inoculated in BG-11 and RSM-optimized BG-11 (ROBG-11) media was tested by cyclic voltammogram studies, revealing the potential of the inoculated strain in ROBG-11 toward photosynthetic algal microbial fuel cells over normal BG-11. To the best of our knowledge, functional group characterization, physical and thermal property and media optimization for EPS production by RSM and electrogenic activity studies are reported for the first time in Scenedesmus sp. SB1.

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Renewable energy resources like biomass from plant and algae have gained more interest for biodiesel production as an energy source to reduce the consumption of fossil fuels and elevated global warming. In this study, Myxosarcina sp., an unicellular cyanobacterium was evaluated for higher biomass and lipid production by the supplementation of sugar industrial waste (SIW), sodium chloride (NaCl) and media optimization with response surface methodology (RSM) for biodiesel production. The outcome of the findings showed that biomass and lipid productivities of 28.5 ± 2.4 (1.2 fold) and 3.4 ± 0.2 (1.3 fold) mg/L/day were observed in the BG-11 media supplemented with SIW than control (24 ± 1 and 2.6 ± 0.4 mg/L/day). However hyper lipid content 20.6 ± 1.8 % (1.5 fold) was achieved by RSM optimized media including NaCl at 0.8 M, SIW at 2 mL/L, sodium nitrate (NaNO3) at 2.5 g/L and magnesium sulphate (MgSO4) at 0.075 g/L than control (13.6 ± 1.4 %). Fatty acid characterization by GC-MS anlysis revealed that Myxosarcina sp. yielded 39 ± 5.3 % of saturated fatty acids (SFA) and 61 ± 5.3 % of mono unsaturated fatty acid (MUFA) and its biodiesel fuel properties evaluated using empirical equations showed that almost all the properties calculated were in concurrence with the national and international biodiesel standards EN 14214 (Europe), ASTM D6751-02 (US) and IS 15607 (India). Thus, Myxosarcina sp. can be utilized as the environmental friendly biodiesel feedstock for high quality biodiesel production in the current scenario for the escalating energy demand.

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Microalgae are considered as potential feedstock for biodiesel production. In this study, a new green microalga was isolated from a freshwater pond in India and identified as Meyerella sp. N4. Nutrient starvation strategy was employed in this strain to understand the enhancement of the lipid accumulation. The increase in accumulated lipid was further confirmed by Nile red staining, followed by confocal laser scanning microscopic observation. Nitrogen (NaNO3) starvation increased the lipid accumulation up to 60.4 ± 3.7% of dry cell weight at 314 ± 13 mg of total lipid/L in 23 days, when compared to the other conditions tested. Quantification of total fatty acid content by gas chromatography–mass spectrometry showed the presence of two major fatty acids, C16 at 34 ± 4.8 wt %, and C18:1 at 26 ± 3.6 wt %. Biodiesel quality parameters, such as cetane number at 57.7 ± 0.3, iodine value at 77.7 ± 1.1 g of I2 100 g–1 of oil, saponification value at 190.5 ± 1.8 mg of KOH g–1 of oil, and the cold filter plugging point at −1.5 ± 1.0 °C, are in good agreement with the international standards, American standard ASTM D6751 and European standard EN 14214, of biodiesel, thus making Meyerella sp. N4 a potential candidate for biodiesel production.