Characterization and fatty acid profiling in two fresh water microalgae for biodiesel production: Lipid enhancement methods and media optimization using response surface methodology

[Display omitted] •Fresh water indigenous microalgal isolates were characterized as Coelastrella sp. M-60 and Micractinium sp. M-13 as biodiesel feedstock.•The media supplemented with vitamin B12, glucose, citric acid, effluent and salinity stress greatly influenced the biomass, lipid productivity and lipid content by these microalgae.•Media optimization with the variables citric acid and effluent using RSM increased the potential of lipid productivity by microalgae.•FAME characterization and its fuel properties of microalgae are in accordance with the 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±0.4mg/L/day) and Micractinium sp. M-13 (11.1±0.2mg/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.