Highly selective biocatalytic synthesis of monoacylglycerides in sponge-like ionic liquids

Abstract

The biocatalytic synthesis of monoacylglycerides (MAGs) was carried out by the direct esterification of fatty acids (i.e. oleic, palmitic, myristic and lauric acids, respectively) with glycerol in different ionic liquids (ILs) based on cations with long alkyl side-chains (i.e. 1-hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C16mim][NTf2], 1-dodecyl-3-methylimidazolium tetrafluoroborate [C12mim][BF4]). Although all ILs have been shown as suitable reaction media for Novozym 435-catalyzed esterification of glycerol with free fatty acid, a highly selective selectivity of MAGs was only observed for the [C12mim][BF4] case (i.e up to 99% selectivity and yield for the monolaurin case). Furthermore, as these ILs are temperature switchable ionic liquid/solid phases that behave as sponge-like system, a straightforward protocol for IL-free MSGs recovery, based on iterative centrifugations at controlled temperature, has been developed.