Highly efficient solvent-free synthesis of 1,3-diacylglycerols by lipase immobilised on nano-sized magnetite particles

•A nano-sized magnetite cross-linked enzyme aggregate of lipase was developed.•The immobilised lipase’s specific activity of esterification increased 10-fold.•The immobilised lipase can be reused 10times with little loss of activity.•The immobilised lipase retained 90% activity for 36h at 55°C.•High purity 1,3-diacylglycerols were obtained with the immobilised lipase. Recently, 1,3-DAGs (1,3-diacylglycerols) have attracted considerable attention as healthy components of food, oil and pharmaceutical intermediates. Generally, 1,3-DAG is prepared by lipase-mediated catalysis in a solvent free system. However, the system’s high reaction temperature (required to reach the reactants’ melting point), high substrate concentration and high viscosity severely reduce the lipase’s activity, selectivity and recycling efficiency. In this report, MjL (Mucor javanicus lipase) was found to have the best performance in the solvent-free synthesis of 1,3-DAGs of several common commercial lipases. By covalent binding to amino-group-activated NSM (nano-sized magnetite) particles and cross-linking to form an enzyme aggregate coat, MjL’s specific activity increased 10-fold, and was able to be reused for 10 cycles with 90% residual activity at 55°C. 1,3-DAGs of lauric, myristic, palmitic, stearic, oleic and linoleic acid were prepared using the resulting immobilised enzyme, all with yields greater than 90%, and the reaction time was also greatly reduced.