Unlocking the potential of coal mine microalgae strains: Enhanced biodiesel production and CO2 sequestration through cultivation optimization

The harnessing of microalgae for CO2 sequestration and biodiesel production has garnered significant interest due to its potential to mitigate greenhouse gas emissions and provide a renewable energy. The current research delving the dual applications of carbon sequestration efficiency and biodiesel synthesis competence of three microalgal strains of Chlorella vulgaris LCM605, Chlorococcum humicola LCM606, and Quadrigula closterioides LCM607 (hereafter Q. closterioides) isolated from coal mining site, Neyveli, India. Among the tested strains, the Q. closterioides exhibited high lipid content (37.65 % dwt) under CO2 supplementation and was selected in this study. CO2-tolerant microalgae were acclimated to high salinity concentration (100 mM) and enhanced lipid content of 50.94 (% dwt). The highest MUFA content (48.62-95.52 %) was observed in three strains, desirable for biodiesel production. Fuel quality was found to be complying with the limits of international biodiesel standards. To the best of our knowledge, this is the first report validating that coal mine microalgae Q. closterioides has the potential for sequestering CO2 and producing biodiesel under 15 % CO2. This research highlights the potential of Q. closterioides for CO2 sequestration and biodiesel production, emphasizing the importance of optimizing culture parameters for maximizing biomass and lipid yields. This study addresses the research gap in identifying microalgal species with dual functionality for CO2 sequestration and biodiesel production, specifically targeting Q. closterioides from coal mine environment. By assessing its growth and lipid accumulation in this unique setting, the study explores its untapped potential for sustainable bioenergy applications.