Enzymatic transformations. Immobilized A. niger epoxide hydrolase as a novel biocatalytic tool for repeated-batch hydrolytic kinetic resolution of epoxides.

Studies aimed at immobilization of the Aspergillus niger epoxide hydrolase were performed. The use of conventional approaches, i.e. of commercially available supports and classical methodologies, only led to low stabilisation and unsatisfactory enzymatic activity recovery. Therefore, a new strategy based on the use of a "second generation" type of epoxy-activated supports allowing multi-point covalent immobilization, i.e. Eupergit C, partially modified with ethylene diamine (Eupergit C/EDA), and of an adequate experimental procedure was set up. This allowed us to prepare an immobilized biocatalyst with 70%, retention of the initial enzymatic activity and a stabilisation factor of about 30. Interestingly, this biocatalyst also led to a noticeable increase of the E value for the resolution of two test substrates, styrene oxide 1 and p-chlorostyrene oxide 2. This was improved from about 25 to 56 and from 40 to 100, respectively. A typical repeated batch experiment indicated that the thus immobilized enzyme could be re-used for over 12 cycles without any noticeable loss of enzymatic activity or change in enantioselectivity. This therefore opens the way for the use of an 'heterogeneous catalysis' methodology for achieving the preparation of various enantiopure epoxides via biocatalysed hydrolytic kinetic resolution.