Immobilization of feruloyl esterases in mesoporous materials leads to improved transesterification yield

Feruloyl esterases are used in biocatalysis for refinement of hydroxycinnamic acids, a group of compounds with antioxidant and antibacterial properties where modification of solubility is necessary for the compounds to be of interest in different commercial products. In industrially feasible and efficient processes, immobilization of enzymes is often required for sufficient enzyme stability and to enable recovery. In recent years, mesoporous materials have become popular as immobilization support due to advantages such as high protein loading capacity and enhanced enzyme activity because of confinement into pores. We used mesoporous silica, for the first time, as immobilization support for feruloyl esterases. The crude enzyme preparation Depol 740L was adsorbed into two SBA-15 mesoporous silica materials of different pore size and the effects of the immobilization on transesterification of methyl ferulate with 1-butanol into butyl ferulate were studied, tested in a reaction system based on 92.5% 1-butanol and 7.5% MOPS buffer (pH 6.0). Immobilization in mesoporous silica with larger pore size (9 nm) showed higher protein loading and higher specific activity compared to immobilization with smaller pore size (5 nm). Importantly, adsorption into mesoporous silica changed the product specificity of the enzymes to favor transesterification and decrease the rate of hydrolysis compared to free enzymes. The immobilized enzyme had a butyl ferulate yield of up to 90%, significantly higher compared to free enzymes. Additionally, the immobilized enzymes showed an excellent operational stability and reusability, retaining ≥70% of the initial activity after 6 sequential runs, each lasting 6 days. Consequently, we show that mesoporous silica is a robust immobilization support for feruloyl esterases to be used in the development of biocatalysts for customization of the antioxidant properties of hydroxycinnamic acids.