Modulation of metabolic pathway of freshwater microalgae for enhanced biodiesel production and its characterisation

Abstract

The surge in fossil fuel degradation and global warming has led to the invention of biodegradable, renewable, eco-friendly, and less greenhouse gas-emitting biofuel from a renewable feedstock. Microalgae have been considered the preferred feedstock for biodiesel production owing to their high oil content and robust nature. This study explored various optimization approaches to enhance the lipid production of the selected microalgae Tetradesmus obliquus thereby improving their biodiesel production. Initially, eight microalgal strains were isolated from two freshwater lakes located at Puzhal and Ambattur. The isolated algae were maintained in Erlenmeyer flak under white light illumination of 1000 lx with 16:8 photoperiod of light and dark hours respectively. They were identified by their ITS-2 region of 18s rRNA. Biochemical characterization was performed and an in-depth lipid analysis was conducted through qualitative and quantitative analysis. newlineThe synergistic effect of selenium and the gibberellic acid combination on Tetradesmus obliquus was evaluated by central composite design and the maximum lipid and biomass yield of 42.8% and 0.964 g/L/day were determined when supplemented with a combination of selenium and gibberellic acid at newline10 µg/L and 75 µM concentration respectively. The mRNA expression of the FAD enzyme showed a fold change of 4.4 and the ACC enzyme showed a fold change of 1.5 with respect to the control at 10 µg/L and 75 µM concentration of selenium and gibberellic acid. The saturated, monounsaturated, and polyunsaturated fatty acid composition increased with respect to the control and the biodiesel properties were within the ASTM limits with better cold flow properties. newlineThis work elaborates on different approaches for achieving enhanced lipid production from Tetradesmus obliquus with biodiesel characteristics within the ASTM limits. newlineKeywords: newlineBiodiesel, Microalgae, Tetradesmus obliquus, Lipid and Biomass productivity, Fatty acid methyl esters, Biodiesel properties. newline newline