Abstract
A two-enzyme system composed of immobilized ketoreductase (Hansenula polymorpha) and glucose dehydrogenase (Bacillus megaterium) was developed for the asymmetric reduction of keto esters to optically active hydroxy esters via immobilization in polyvinyl alcohol (PVA) gel particles. The concentration of enzymes was optimized, and the final particles were used 18 times in a row in a batch mode to achieve minimal loss of activity and complete conversion of the model substrate, β-ketoester ethyl-2-methylacetoacetate. Excellent stability was also achieved using new storage conditions of PVA particles, with 80% of activity being retained after almost 10 months.
Highlights
Ketoreductases (KREDs) are powerful tools for the asymmetric reduction of ketone substrates to optically active alcohols, which are useful chiral building blocks in chemical and pharmaceutical industries [1]
One study reported the effect of glucose dehydrogenase (GDH) concentration on reaction rate in the kinetic resolution of 11-oxo-5,6,7,8,9,10-hexahydro-6,9-methanobenzocyclooctene and an increasing rate was only observed until 0.15 g·dm−3, while the KRED concentration was 0.2 g·dm−3 [8]
Five different ratios and concentrations of KRED and GDH were used for co-immobilizations (Table 2)
Summary
Ketoreductases (KREDs) are powerful tools for the asymmetric reduction of ketone substrates to optically active alcohols, which are useful chiral building blocks in chemical and pharmaceutical industries [1]. One system used nonporous glass as a support for the KRED and was used in a continuous gas-phase reactor [10]. Another system used covalent binding of KRED on resin EC-HFA, which was applied in both batch mode and flow reactor mode [1]. KRED and GDH were separately immobilized on aldehyde-activated agarose and used in a flow reactor to perform stereoselective ketone reduction [11]. [13]; the co-immobilization of redox enzymes linked with cofactor regeneration limits, etc. [13]; the co-immobilization of redox enzymes linked with cofactor regeneration havenot notbeen beenstudied studied to todate.
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