Biodiesel

Abstract

Biodiesel, which refers to fatty acid alkyl esters, has attracted considerable attention as an environmentally friendly alternative fuel for diesel engines, and biodiesel has several advantages as a renewable, biodegradable, and nontoxic fuel. In this article, various technological methods to produce biodiesel being used in academic and industrial scenarios are reviewed. Several catalytic transesterification processes for biodiesel fuel production have been developed, among which transesterification using alkali catalysis gives high levels of conversion of triglycerides to their corresponding methyl esters in a shorter reaction time and is widely applied for the commercial production of biodiesel. In this article, further emphasis has been given to enzymatic transesterification by considering its advantages in easy separation of byproduct glycerol and the simple downstream processing steps for the recovery of alkyl esters. However, the high cost of the lipase enzyme is the main obstacle for a commercially feasible enzymatic production of biodiesel fuels. To reduce enzyme-associated process costs, the immobilization of lipase-producing fungal mycelium within biomass support particles as well as expression of the lipase enzyme on the surface of yeast cells have been developed to generate whole-cell biocatalysts for industrial applications. The cost of lipase production can be further lowered using recombinant gene technology, such as by developing microorganisms with high expression levels of lipases and stability of lipases toward methanol.