Construction of an immobilized thermophilic esterase on epoxy support for poly(ϵ-caprolactone) synthesis

Developing an efficient immobilized enzyme is of great significance for improving the operational stability of enzymes in poly(ϵ-caprolactone) synthesis. In this paper, a thermophilic esterase AFEST from the archaeon Archaeoglobus fulgidus was successfully immobilized on the epoxy support Sepabeads EC-EP via covalent attachment, and the immobilized enzyme was then employed as a biocatalyst for poly(ϵ-caprolactone) synthesis. The enzyme loading and recovered activity of immobilized enzyme was measured to be 72 mg/g and 10.4 U/mg using p-nitrophenyl caprylate as the substrate at 80°C, respectively. Through the optimization of reaction conditions (enzyme concentration, temperature, reaction time and medium), poly(ϵ-caprolactone) was obtained with 100% monomer conversion and low number-average molecular weight (M_n < 1300 g/mol). Further, the immobilized enzyme exhibited excellent reusability, with monomer conversion values exceeding 75% during 15 batch reactions. Finally, poly(ϵ-caprolactone) was enzymatically synthesized with an isolated yield of 75% and M_n value of 3005 g/mol in a gram-scale reaction.