Tropho-metabolic transition during Chlorella sp. cultivation on synthesis of biodiesel

• Heterotrophic transition resulted in increase of both total and neutral lipids.
• Mixotrophic mode showed higher biomass and lipid productivities.
• C16:0 and C18:2 were specifically overproduced in heterotrophic transition.
• Carbon supplementation influences fatty acid profile during microalgae growth.

Mixotrophic and heterotrophic cultivation modes were studied for enhancing the biomass and lipid productivities using light and carbon as critical factors. The adaptability of the newly isolated Chlorella sp towards transition from mixotrophic to heterotrophic cultivation mode was evaluated. Organic carbon illustrated higher affinity towards both biomass and lipid productivities. Specific changes in fatty acid profile were observed with respect to trophic condition. Maximum biomass productivity (4.21 g/l) and relatively higher lipid productivity (107.3 g/kg of DCW) was observed with mixotrophic (MXG) condition while heterotrophic mode showed higher lipid content (28.9%). Higher carbohydrate content (94.3 mg/g DCW) was observed in mixotrophic mode and maximum protein content (450 mg/g DCW) was obtained with heterotrophic condition. The synergism between total lipid content, fatty acid composition and biomass productivities during trophic transition was critically evaluated. The transition between the trophic modes have given deeper insights into the metabolic partitioning of carbon in photosynthetic and respiratory pathways during synthesis of biodiesel precursors. Mining of bio-based products from microalgae can create more sustainable economies and integrated approach will add paybacks to process signifying algal based biorefinery model.