Comparative study of properties of immobilized lipase onto glutaraldehyde-activated amino-silica gel via different methods

The enzyme-aggregate coating method was performed to immobilize Arthrobacter sp. lipase in order to achieve better catalytic properties comparable to the conventional covalent attachment and covalent attachment plus cross-linking. The glutaraldehyde-activated amino-silica gel which was synthesized by sol–gel technique was used as the support, and the catalytic characteristics of the lipase preparations were tested in the asymmetric acylation of 4-hydroxy-3-methyl-2-(2-propenyl)-2-cyclopenten-1-one (HMPC) in organic solvents. The results showed that the immobilized lipase by enzyme-aggregate coating possessed both higher activity and stability than those by other methods, e.g. it obtained an activity of 82.6 U/g and remained 42% and 93% of the original activity after incubation in vinyl acetate at 60 °C for 16 h and 9 times recycles, respectively, while the covalently attached lipase got an activity of 67.4 U/g and left 33% and 73% of the original under the same conditions, and the enzyme prepared by covalent attachment plus cross-linking exhibited the lowest activity yield. Moreover, excellent enantioselectivity (E ≥ 400) was achieved by all the three prepared lipases in our paper (E = 85 for the free enzyme).