Optimization of process parameters on lipid biosynthesis for sustainable biodiesel production and evaluation of its fuel characteristics

•Identification of cyanobacterium.•Optimization of process parameter on yield of lipid and its composition.•Characteristics of microalgal lipid and biodiesel. The isolation of ten different cyanobacteria were carried out from northern parts of India and among them the cyanobacterium with maximum specific growth rate (0.246 day−1) was selected for the present study. The strain was further identified using morphometric and molecular analysis using 16S rDNA sequencing and was found to be related with Leptolyngbya sp. (GenBank accession no.: KF953500). The analysis of biomass composition showed ash content, amount of carbohydrate, lipid content, amount of protein, and moisture were found to be 6.8, 27.20, 18.30, 45.70, and 2% respectively. Over 26.6% increment in lipid content was evidenced when the strain was grown in BG11 medium augmented with salinity (25 mM sodium chloride) as compared to BG11 medium without sodium chloride. The unsaturated fatty acids was found 1.39 times higher than saturated fatty acids in KF953500. The lipid separated from cyanobacteria showed saponification value of 220.28, iodine value of 84.08, cetane number of 52.16, degree of unsaturation of 84.04 (%), long-chain saturation factor of 3.09 (%) and cold-filter plugging point of −6.76 °C which are generally in covenant with international standards of biodiesel. Other biodiesel properties such as pour point, flash point, acid number, viscosity, specific gravity, and density were found to be −18 °C, 126 °C, 0.34 mg KOH/g, 4.08 mm2 s−1, 0.812, and 854 kg m−3 respectively which falls within the acceptable ranges as per ASTM D6751 and EN 14214 standards, signifying the aptness of the microalga as promising sustainable feedstock for biodiesel.