Comparison of bio-imprinted Aspergillus niger lipase by oleic acid or olive oil to improve esterification performance

To compare the catalytic characteristics of substrate analogs of fatty acids or triglycerides in bio-imprinted lipase, bio-imprinted lipase with oleic acid or olive oil was chosen for investigation. Bioimprinting was combined with resin adsorption immobilization to catalyze the synthesis of sucrose-6-acetate via ester exchange of sucrose with vinyl acetate as a test reaction. Under optimal conditions, the bio-imprinted lipase with oleic acid catalyzed the reaction with an esterification rate of sucrose of 90.6 f 1.2 % and an esterification of the 6-position hydroxyl group of sucrose of 92.4 f 1.0 %, while the bio-imprinted immobilized lipase with olive oil catalyzed the reaction with an esterification rate of sucrose of 91.9 f 1.3 % and an esterification of the 6-position hydroxyl group of sucrose of 93.3 f 1.2 %, which were similar to the catalytic performances of both bio-imprinted lipases. The secondary structure of bio-imprinted immobilized lipase can be characterized by Fourier transform infrared spectroscopy (FTIR) with a decrease in alpha-helix and an increase in beta-sheet, which suggests the bio-imprinting caused a change in conformations of the lipase protein. Raman spectroscopy results revealed that the structural alterations that occurred in the lipase during the bioimprinting process of oleic acid or olive oil were different. Fluorescence spectroscopy analysis demonstrated that the amino acid microenvironment in the active center of the bio-imprinted lipase became progressively more hydrophobic as the bioimprinting time increased, thereby enhancing the catalytic activity. Structural analysis of the bio-imprinted lipase revealed that the structural alterations in the lipase proteins were different when oleic acid or olive oil were the bio-imprinted molecules. Fatty acids or triglycerides as substrate analogs for the esterification reaction of bio-imprinted lipase can improve catalytic performance and have ideal application prospects.