Engineering of Cascade Reactions and Alditol Oxidase for High‐Yielding Synthesis of (R)‐Phenylethanolamine from Styrene, l‐Phenylalanine, Glycerol or Glucose

Abstract ( R )‐phenylethanolamine (PEA) is a useful and valuable chiral chemical and requires enantioselective and efficient synthesis method. A novel SMO‐StEH‐AldO‐CvTA‐catalyzed cascade reaction was established to convert styrene to ( R )‐PEA via epoxidation‐hydrolysis‐oxidation‐amination. The key transformation of ( R )‐1‐phenyl‐1,2‐ethanediol to ( R )‐PEA in the cascade was achieved in 94 % conversion via AldO‐CvTA. The limiting enzyme AldO was engineered through directed evolution, yielding a mutant AldO(MVIK) with 3‐fold enhanced catalytic efficiency. The use of AldO(MVIK) in the 4‐enzyme cascade significantly increased the productivity than the use of AldO, yielding 34.6 mM ( R )‐PEA with >99 % ee . By incorporating deamination and decarboxylation enzymes, a 6‐enzyme cascade was engineered to produce 23.7 mM ( R )‐PEA from l ‐phenylalanine. Coupling of l ‐phenylalanine biosynthesis pathway with 6‐enzyme cascade enabled synthesis of ( R )‐PEA from glycerol or glucose, producing 6.8 mM and 6.5 mM ( R )‐PEA, respectively. The developed cascade biotransformations provide direct synthesis of ( R )‐PEA from either simple chemicals or renewable feedstocks.