Highly active and recyclable immobilized multiple enzymes for one-pot enantioselective cascade reactions: Synthesis of (R)- and (S)--amino acids from racemic -hydroxy acids

Cascade biotransformation of racemic alcohols to enantiopure amines is highly wanted in pharmaceutical manufacturing but requires green and efficient solution. Here we developed the first immobilized enzyme-based approach for this transformation, being cleaner and more productive than whole-cells biocatalysis, and more economic and higher-yielding than using isolated enzymes. As demonstration, the conversion of racemic mandelic acids to high-value (R)- or (S)-phenylglycines was achieved by immobilized enantioselective alcohol oxidase, racemase, catalase, and (S)- or (R)-transaminase. Co-immobilization of the four enzymes on Ni-NTA functionalised carriers gave high enzyme loadings (192-195 mg enzyme/g carrier), loading efficiencies (97-98%), and free enzyme activities (107-113%). Immobilized enzymes transformed racemic mandelic acids to the corresponding four (S)-phenylglycines in 91-99% ee and 82-95% yields or five (R)-phenylglycines in 93-99% ee and 83-94% yields. These catalysts showed good recyclability, retaining 86-98% productivities in the fifth reaction cycles.