Sustainable biomass production under CO2 conditions and effective wet microalgae lipid extraction for biodiesel production

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Abstract The freshwater microalga Chlorella vulgaris MSU AGM 14 was cultured at different CO2 conditions (up to 8%) with 100 μmol photons m−2 s−1 to evaluate biomass and lipid productivity. For effective extraction of intra-cellular lipids, a novel method based on mild pressure (1–2.5 kg/cm2) with short period (5–15 min) of heat shock (50–70 °C) were studied for the wet biomass. The transesterified lipids were qualitatively and quantitatively analysed using Gas Chromatography coupled with Mass Spectrometry (GC-MS). The higher CO2 aeration (8%) significantly increased the biomass productivity (23%) when compared with control and CO2 (4%) aeration. Total lipid production (93%) acquired by conventional extraction procedure showed enhanced production simultaneously. The maximum lipid recovery (0.225 g g−1 dw) was obtained at a pressure of 2 kg/cm2 and heating for 10 min at 60 °C. The transesterified lipids showed that oleic acid (C18:1–51.62%) was the main component in both conventional and suggested lipid extraction process. The suggested extraction process showed significant increase in biodiesel yield by 26.7%. The energy outputs of biodiesel by conventional and suggested extraction process were 417.7 and 533.6 MJ ton−1, respectively. The overall results indicated that 8% of CO2 induced the biomass and lipid productivity by 94% and 54.8%, respectively, when compared with control. In addition, the suggested mild pressure with heat shock extraction process further enhanced the lipid recovery by 21% which serves as a cost-effective lipid extraction process for microalgae.