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

Abstract

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.