Enhancing enzyme activity and enantioselectivity of Burkholderia cepacia lipase via immobilization on melamine-glutaraldehyde dendrimer modified magnetic nanoparticles

Burkholderia cepacia lipase (BCL) was a potential catalyst in chiral resolution. Immobilization can be used to increase the enzyme activity and operational stability. In this work, novel melamine-glutaraldehyde dendrimer-like polymers were firstly grafted on the aminated magnetic nanoparticles to increase protein binding sites for the lipase to be immobilized. The dendrimer-polymer-modified nanoparticles could obviously protect the conformation of lipase and increase the contact chance between substrates and catalyzed center of lipase. The standard esterification reaction between lauric acid and 1-dodecanol was used to test the lipases activities. The activity of the obtained immobilized lipase was 58.0-fold than BCL powder, and 3.0-fold than the immobilized lipase without modified polymers. Then, the immobilized lipase was used to catalyze the chiral resolution reaction between 1-phenylethanol and vinyl acetate. Different organic solvents were selected for chiral resolution reaction. It was found out that hexane and heptane were the best reaction media. Thermal stability and organic solvent tolerance of the immobilized lipase were greatly improved than those of the lipase powder. The most significant discovery was the improvement in enzyme activity by bioimprinting. It could greatly shorten the reaction time from 3 h to 20 min. The conversion and substrate enantiomeric excess (ee(s)) reached 49.7% and 98.8% in 20 min, respectively. The immobilized lipase could be recycled for 8 times without obvious loss in activity. The study provides a good strategy for preparation of efficient biocatalyst, showing great potential for future industrial application.