Immobilization in MPS and characterization of a FAE for hydrolysis and transesterification reactions.

Conference poster, 2015

Enzymes display high reactivity and selectivity under normal conditions, but may suffer from denaturation in industrial applications. A strategy to solve this limitation is to immobilize enzymes. Mesoporous silica materials (MPS) are an interesting choice as support to immobilized enzymes because MPS offer unique properties such as high enzyme loading and tunable pore size. Immobilization parameters such as pH, buffer and pore size of the MPS were investigated on a commercially available feruloyl esterase (FAE). Among them, the chemical composition of the buffer as well as its pH proved to be critical for optimal immobilization resulting in enzyme loadings varying from nearly zero up to 0.025 mgenzyme.mgMPS-1. Selectivity of the enzyme was investigated by quantifying the molar ratio between the transesterification and hydrolysis products, namely butyl ferulate (BFA) and ferulic acid (FA). The immobilization pH and the water content of the reaction mixture were parameters influencing the molar ratio of BFA/FA, leading to up to 4-folds higher ratios. Optimal reaction conditions and kinetic parameters of the free and immobilized enzyme were determined. Then stability of the enzyme was evaluated using the hydrolysis reaction. Surprisingly, no significant stability improvement could be observed for the immobilized enzyme compared to the free enzyme. Reusability of the immobilized biocatalyst was determined during 10-cycles of 48h. A decrease in activity was observed during the course of the experiment associated with a decrease in the BFA/FA molar ratio indicating a shift in enzyme specificity. This study was a first step in understanding how immobilization in MPS affects FAE activity and selectivity. MPS showed to be an interesting support material for FAE immobilization since MPS allow robust enzyme immobilization through simple physical adsorption without affecting some of the kinetic parameters of the FAE.