Preparation of Immobilized Lipase Based on Hollow Mesoporous Silica Spheres and Its Application in Ester Synthesis

In this study, Candida rugosa lipase (CRL) was immobilized into modified hollow mesoporous silica (HMSS) materials with different hydrophobicity. Among propyl-(C(3)), phenyl-(C(6)), octyl-(C(8)), and octadecyl-(C(18)) modified HMSS as well as native HMSS, taking advantage of more hydrophobic microenvironment, the HMSS-C(18)-CRL showed exceptional performance in enzymatic esterification reaction. Using the novel HMSS-C(18) with immobilized CRL (HMSS-C(18)-CRL), we investigated the esterification of phytosterols with polyunsaturated fat acid (PUFA) in a solvent-free system for the production of phytosterols esters. Response surface methodology (RSM) was applied to model and optimize the reaction conditions, namely, the enzyme load (5–25%), reaction time (10–110 min), molar ratio of α-linolenic acid (ALA)/phytosterols (1:1–7:1) and represented by the letters E, T, and M respectively. Best-fitting models were successfully established by multiple regressions with backward elimination. The optimum production was achieved at 70 min for reaction time, 20% based on the weight of substrate for enzyme loading, and 5.6:1 for ALA/phytosterols molar ratio. Under optimized conditions, a conversion of about 90 ± 2% was achieved. These results indicated that HMSS-C(18)-CRL demonstrates to be a promising catalyst and can be potentially applied in the functional lipid production.