LAUSR

Abstract Algal lipids are prospective sustainable and economic resources for biodiesel. In this study, growth parameters i.e. lipid, biomass, and total chlorophyll contents of the two algal consortia S1 and S16 were optimized at varied pH microenvironment, different nutrient media and NaNO3 concentrations. Results obtained from the present study revealed that optimum growth of the consortia S1 in terms of lipid, biomass, and total chlorophyll was observed at pH 7 while for S16 it was at pH 8. Optimum protein contents for S1 and S16 were obtained at pH 6 and 5, respectively. For both the consortia, BG-11 was found to be the best-suited medium for biomass, total chlorophyll and protein contents, whereas the highest lipid accumulation was favored by the Bold Basal Medium. The present study demonstrated that nitrogen deprivation in the medium would favor high lipid accumulation. About 1.0 g L−1 of sodium nitrate (NaNO3) was found to be suitable for enhancing the biomass yield and total chlorophyll while the concentration required for optimum lipid and protein content was observed to be 10 folds lower at 0.1 g L−1. Consequently, under nitrate stress, the lipid content of S1 was observed to increase by 55.5% as compared to control. Surface morphology of algal cells was explored with the help of Scanning Electron Microscopy (SEM) under normal as well as stress conditions (0.1 g L−1 NaNO3). Nitrate stress was found to exert significant effects on cell morphologies of both the algal consortia. Fourier Transform Infrared (FTIR) spectra of both the consortia revealed the presence of various functional groups corresponding to lipid, carbohydrate, and protein under normal and stress conditions.