Heterotrophic cultivation of mixed microalgae for lipid accumulation and wastewater treatment during sequential growth and starvation phases: Effect of nutrient supplementation

Microalgae are deemed to be a potential biocatalyst for the production of biodiesel along with other valuable products. An attempt was made to evaluate the effect of sequential growth phase (GP) and starvation phase (SP) on the lipid productivity of heterotrophically grown mixed microalgae using domestic wastewater as substrate/feed-stock. Effect of nutrients viz., nitrogen (N), phosphorus (P), carbon (C) and potassium (K) on biomass growth and lipid accumulation was elucidated. Due to good nutrients availability during GP operation, significant increment in biomass growth was observed. On the contrary, nutrients deprived condition during SP operation documented increment in lipid productivity due to acceleration of triacylglycerides formation. Higher biomass growth was observed in GP operation with maximum in N + P condition (1.69 mg/mL) while higher lipid productivity was observed in starvation phase with maximum in C condition (28.2%). Gross fatty acid composition depicted significant variations in the fatty acid profile with abundance in saturated fatty acids (SFAs). Relatively good wastewater treatment efficiency in terms of substrate degradation and nutrient removal was observed during the GP operation. Diversity studies visualized dominance of lipid accumulating microalgae such as Scenedesmus sp., Diatoms and Chlorella sp.

► Influence of two phase operation in microalgae for lipid accumulation is studied under heterotrophic conditions.
► Effect of various nutrients on biomass and lipid productivity in microalgae is evaluated.
► Gross fatty acid profile with respect to the various nutritional attributes is discussed in detail.
► Variations in the lipid productivity profiles is studied at two phases of operation.
► Diversity analysis of mixed microalgae was performed for each nutrient condition.