Trace water activity could improve the formation of 1,3-oleic-2-medium chain-rich triacylglycerols by promoting acyl migration in the lipase RM IM catalyzed interesterification

New structured lipids with 1,3-oleic-2-medium chain (OMO) triacylglycerols were synthesized by promoting acyl migration in Lipozyme RM IM catalyzed interesterification between coconut oil (CO) and high oleic rapeseed oil (HORO). Results from an orthogonal design L25(55) showed that the maximal yield of OMO-structured triacylglycerols was 45.65% under the following conditions: the molar ratio of CO to HORO, 50:50; enzyme dosage, 12 wt%; reaction temperature, 60 °C; reaction time, 2 h; water activity, 0.07. Low water activity showed a high rate of acyl migration (10.86% vs 5.07% no water system), which promoted OMO synthesis due to medium-chain fatty acid migration to the sn-2 position. In a low water content (5%) system of the molecular dynamics simulation, water molecules stabilized the whole structure of RM IM through hydrogen bonding, which helped fix lipase-catalyzed active sites, making substrates more easily inserted into active sites, resulting in increased enzyme activity.