Effect of gamma irradiation on lipid accumulation and expression of regulatory genes involved in lipid biosynthesis in Chlorella sp.

摘要

Microalgae are promising species with high potential for biodiesel production. Large-scale cultivation of oleaginous microalgae in industrial effluents and municipal wastewater provides dual benefits of biodiesel production and wastewater treatment. Such approach to biodiesel production does not interfere with conventional agricultural resources and practices. Microalgae can accumulate lipid under various stress conditions. In this study, gamma irradiation was used for the first time as a stressor to trigger lipid accumulation in two strains of Chlorella sorokiniana. Gamma irradiation enhanced the lipid content of more than 40% of biomass. Intracellular reactive oxygen species generated by gamma ray exposure was measured by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining under flow cytometry. Cytoplasmic lipid droplets were observed by Nile red staining using fluorescence microscopy. Expression patterns of regulatory genes involved in lipid biosynthesis, namely acetyl-CoA carboxylase and diacylglycerol acyl transferase, were upregulated immediately after irradiation and were highest 3 days post irradiation. This novel strategy of using gamma radiation as a faster and extremely potent stressor for triggering lipid biosynthesis in microalgae has immense potential in industrial biodiesel production.