GLYOXYLIC-ACID PRODUCTION USING MICROBIAL TRANSFORMANT CATALYSTS

A practical method for the biocatalytic oxidation of glycolic acid to glyoxylic acid which uses a genetically engineered microbial cell as catalyst has been developed. Oxidations of glycolic acid at concentrations ranging from 0.75 to 1.5 M were run in aqueous solution in the presence of oxygen, ethylenediamine, and a metabolically inactive transformant of Aspergillus nidulans, Hansenula polymorpha, Pichia pastoris, or Escherichia coli. Each of the transformant catalysts contained significant quantities of both spinach glycolate oxidase ((S)-2-hydroxy acid oxidase, EC 1.1.3.15) and an endogenous catalase (EC 1.11.1.6). The H. polymorpha and P. pastoris transformant catalysts were recycled in up to 30 consecutive batch reactions, where the selectivity to glyoxylic acid was typically >98% at 100% conversion of glycolic acid. Under optimum reaction conditions and with endpoint monitoring, selectivities to glyoxylic acid of at least 99.7% were obtained.