The Realm of Lipases in Biodiesel Production

Lipases are the enzymes known for the hydrolytic activity on carboxylic fatty ester bonds. The industrial interest in lipases is due to their application in a wide array of products: in detergents and cleaning products, in pharmaceutical applications, in the food industry, and on the production of biodiesel. Biodiesel, i.e. short-chain-acyl fatty ester, is mainly produced via the transesterification of fatty-acyl glycerides or esterification of fatty acids, both reactions with a short chain alcohol. Lipases can catalyze both said reactions with high specificity, producing biodiesel at high yields at low temperature. With the significant advances in biodiesel production over the last decades, coupled with a strong industrial partnership, the costs of utilizing lipases as catalysts have dropped significantly. The production of lipases became popularized in the industry due to advances not only in the reaction mechanisms, and in better understanding of lipase-producing microorganisms, but to cost-effective utilization practices. Immobilization is the practice responsible for the initial breakthrough innovation that allowed efficient reutilization of lipases, thus reducing the cost per batch. There was, and still there is, numerous advances in the development of immobilizing matrices and novel utilization pathways of immobilized enzymes available in the literature. More recently, other methods of using lipase in biodiesel production have been developed, e.g. via the utilization of whole-cell and fermented solid with lypolytic activity, and by the use of lipase in liquid formulations. Over the last years, there has been an increased interest in developing next-generation biodiesel, i.e., the one produced from alternative lipid feedstock, such as microbial and residual lipids, and by utilizing ethanol as acyl agent, instead of methanol. There has also been prominent advances in the reactor engineering aspect of lipase-derived biodiesel, by promoting more efficient batch processes, and the development of lower-cost continuous processing. The present chapter reviews the recent literature in the important field of using lipases in biodiesel production, and critically describes the opportunities and challenges present in such applications.