Biodiesel synthesis from wastewater grown microalgal feedstock using enzymatic conversion: A greener approach

Commercial scale microalgal biodiesel production is still challenging due to high cultivation cost and inefficient conversion technologies. This work explicated an economical cultivation strategy using anaerobic centrate as growth medium of Acutodesmus obliquus. Among various modes evaluated maximum lipid productivity of 57.03 mgL(-1)d(-1) was achieved under mixotrophic cultivation condition using anaerobic centrate. Conversion of microalgal lipids to biodiesel using immobilized Candida rugosa lipase was investigated. Reaction parameters viz. temperature, methanol to oil molar and enzyme amount were optimized using response surface methodology. Best conversion of 95.36% was achieved at 50 degrees C, methanol to oil ratio of 3:1 and 15% enzyme amount based on oil weight. Immobilized C. rugosa lipase can be used for 5 batches without much loss in conversion efficiency ( > 90%). Most of the fuel properties comply with ASTM and EN standards.