Process-intensified in-situ transesterification of wastewater-grown Marvania coccoides biomass using immobilized lipase for biodiesel production

Microalgae can serve as a potential raw material for the development of sustainable biodiesel production. This study explores biodiesel production from Marvania coccoides cultivated in nutrient optimized wastewater (OWW), with a primary focus on evaluating and comparing in-situ and ex-situ transesterification processes. The OWW biomass achieved 937.5 ± 17.68 mg.L^-1 biomass yield with lipid content of 19.8 ± 0.99 %, indicating the suitability for biodiesel production. The elemental analysis showed high carbon and oxygen content, supporting its potential for biofuel. The acid value of microalgal lipids was found to be 10.71 ± 0.72 mg KOH.g^-1 indicating the necessity for enzyme and acid catalysis. Transesterification carried out using ex-situ and in-situ methods showed the highest fatty acid methyl esters (FAME) yield of 91.95 ± 0.32 % and 72.54 ± 0.84 %, respectively with immobilized lipase as catalyst. However, further process intensification assisted by sonication enhanced the FAME yield of in-situ transesterification, which showed a maximum FAME yield of 90.65 ± 0.77 % with immobilized lipase as a catalyst. Further, the catalyst reusability study demonstrated that immobilized lipase showed FAME yield of 64.2 ± 0.84 % in the fourth cycle. GCHRMS analysis revealed the presence of major fatty acids enhancing biodiesel quality. The biodiesel fuel properties comply with ASTM D6751 and EN 14,214 standards, indicating the potential of microalgae in biodiesel production through in-situ transesterification.