Strategy for lipid extraction and transesterification to enhance Chlorella sorokiniana strain BV 12 feedstock utilization

Abstract

Efficient production and recovery of fatty acid methyl esters (FAMEs) from lipid containing feedstock is the key step of biodiesel production. This enhances the utilization of feedstock and improves the final economics of the process. Currently, direct and indirect transesterification strategies are being employed for biodiesel production from microalgae with few reports of tailoring the process to a specific feedstock. In this study, Chlorella sorokiniana strain BV 12 was grown in modified BG-11 medium and biomass was harvested. This was subjected to different physical, chemical and physico-chemical strategies for increasing the transesterification yield. The transesterified lipid was evaluated for various biodiesel properties like iodine value, saponification value, acid value, peroxide value and cetane number. After harvesting, gravimetric lipid yield of 161.7 mg/g and 4117.5 µg/g of FAME were obtained. Extraction of lipid was dependent on the cell disruption technique as it is accumulated intracellularly as droplets. Sonication resulted in maximum FAME production using either dry (4724.2 µg/g) and wet (4835.8 µg/g) biomass which shows that wet biomass is more suitable for processing. Gravimetric results favour the extraction by sonication showing a 63.22% increase in lipid recovery. Testing of different solvents for extraction showed methanol as most favourable for FAME analysis with acidic catalyst like HCl and H2SO4 giving FAME with better ignition value (∼51, Cetane number).