Co-Cross-Linked Aggregates of Baeyer–Villiger Monooxygenases and Formate Dehydrogenase for Repeated Use in Asymmetric Biooxidation

Abstract

Baeyer–Villiger monooxygenases (BVMOs) are versatile biocatalysts, but their applications are hindered by their poor stability and cofactor dependence. In this study, cross-linked enzyme aggregate (CLEA) technology was adopted to coimmobilize BVMO and its accessory cofactor-regeneration enzyme. Combi-CLEAs of a pyrmetazole monooxygenase from Acinetobacter calcoaceticus (AcPSMO) and a formate dehydrogenase from Burkholderia stabili (BstFDH) were prepared for the synthesis of (S)-omeprazole. After optimization, AcPSMO and BstFDH were coprecipitated with an activity ratio of 1:6 using ammonium sulfate and then cross-linked with glutaraldehyde (0.12% w/v). The activity recoveries of AcPSMO and BstFDH in the prepared combi-CLEAs were 43% and 38%, respectively. Compared with the free enzymes AcPSMO and BstFDH, the thermostabilities of AcPSMO and BstFDH in combi-CLEAs were improved by 2.5- and 1.6-fold, respectively. Both enzymes were more stable against alkaline buffer after being immobilized. The combi-CLEAs could be reused for seven cycles in the biooxidative synthesis of (S)-omeprazole without significant activity loss, indicating the excellent operational stability and reusability in repeated reactions for the enzymatic synthesis of (S)-omeprazole. Another two combi-CLEAs prepared under the same conditions, TmCHMO–BstFDH and RpBVMO–BstFDH, can be reused for at least 15 consecutive batches for the cyclohexanone mono-oxygenation reaction, which indicates the promising potential for coimmobilization of BVMOs and FDH with CLEA methodology.