The acyltransferase activity of lipase CAL‐A allows efficient fatty acid esters formation from plant oil even in an aqueous environment

Abstract

The enzymatic synthesis of fatty acid esters (FAE) can be performed by lipases in reaction systems in the absence of bulk water. However, some lipases such as Candida antarctica lipase A (CAL-A) have an acyltransferase activity, which enables FAE synthesis from natural oils and suitable alcohols even in the presence of water. The ability to generate these compounds in an aqueous system would be interesting for an industrial application, because this could lead to a more cost-efficient and environmentally friendly process as the alcohol donor also serves as solvent. Using refined palm kernel oil (PKO) the CAL-A-catalyzed ester synthesis was studied with methanol or ethanol in the presence of 5-10% (w/w) water. Optimizing reaction parameters (e.g., temperature and water content) resulted in up to 95% ester formation after 24 h. In addition, methanol allowed higher ester formation than ethanol.Practical applications: The enzymatic synthesis of fatty acid esters from plant oils using standard lipases is hampered by the fact that the presence of water leads to undesired formation of free fatty acids. The use of CAL-A with its unique acyltransferase activity overcomes this limitation and hence makes the industrial scale synthesis of these esters more feasible. The identification of important parameters influencing the ester formation is crucial to establish such processes.Abbreviations: CAL-A, Candida antarctica lipase A; PKO, palm kernel oil Eur.

How the Same Core Catalytic Machinery Catalyzes 17 Different Reactions: the Serine-Histidine-Aspartate Catalytic Triad of α/β-Hydrolase Fold Enzymes

“…Several lipases favor acyl transfer to alcohols 59,72,73 or hydroxylamine 74–76 ( over hydrolysis even in aqueous solution. For example, lipase from Candida parapsilosis converts ethyl oleate and hydroxylamine to the oleylhydroxamic acid in 40% yield.…”

Recent Insights and Future Perspectives on Promiscuous Hydrolases/Acyltransferases

“…Recent research on promiscuous hydrolases/acyltransferases started in 1993 when CpLIP2, a lipase from Candida parapsilosis , was discovered and shown to be able to catalyze the synthesis of oleoylesters of ethylene glycol, ethanol, n -propanol, and isopropanol in aqueous systems . Homologous lipases, phylogenetically related to Pseudozyma antarctica (formerly named Candida antarctica ) lipase A (CAL-A), shared this promiscuous acyltransferase activity, which could be used to produce fatty acid methyl or ethyl esters (biofuels) in the presence of water. − The acyltransferase activity of CAL-A could be improved by a single mutation (D122L), allowing up to 95% fatty acid ethyl ester to be produced from palm kernel oil in the presence of aqueous ethanol. − CAL-A’s promiscuous acyltransferase activity was further used in a cascade reaction with an alcohol dehydrogenase and a Baeyer–Villiger monooxygenase (BVMO) to reduce product inhibition and shift the reaction equilibrium toward product formation by catalyzing the oligomerization of the ε-caprolactone produced from cyclohexanol . This example demonstrates the value of acyltransferases that can be employed in biocatalytic cascades in water.…”

Main Structural Targets for Engineering Lipase Substrate Specificity

“…This product is marketed for degumming edible oil (Lecitase ultra™, Novozymes A/S). In the fatty acid derived from palm oil synthesis, the Candida antarctica lipase A acyltransferase activity has been implemented, even in the presence of 5-10% (w/w) water [163]. The Novozyme 435 lipase has been efficiently implemented in free fatty acids with octanol esterification to produce octyl esters, hence, the modification of vegetable oils to form bio lubricant components can be successfully achieved by exploiting lipase-catalyzed transesterification, esterification, epoxidation reactions [164].…”