A Novel Microbial Aldehyde Oxidase Applicable to Production of Useful Raw Materials, Glycolic Acid and Glyoxylic Acid, from Ethylene Glycol

Glycolic acid is an attractive raw material which is used as a dyeing and tanning agent in the textile industry, a flavoring agent and preservative in the food processing industry, and a skin care agent in the pharmaceutical industry. It is also utilized for the production of polyglycolic acid and other biocompatible copolymers. Glycolic acid can be isolated from natural sources, such as sugarcane, sugar beets, pineapple, or cantaloupe, but it is also chemically synthesized by hydrogenation of oxalic acid with nascent hydrogen or the hydrolysis of the cyanohydrin derived from formaldehyde. Ethylene glycol is a relatively inexpensive starting material for the production of glycolic acid by an oxidation reaction. However, the chemical oxidation reaction of ethylene glycol has certain drawbacks, such as the formation of formaldehyde and other compounds as by-products. To overcome such drawbacks of chemical synthesis for the production of glycolic acid, one of the preferred methods is to use enzymatic production rather than chemical synthesis. The utilization of microbial enzymes also has the major advantage of promoting simple and eco-friendly industrial-scale production. We therefore designed a new enzymatic method for the production of glycolic acid from ethylene glycol using two microbial oxidases; ethylene glycol is first converted to glycolaldehyde by an ethylene glycol-oxidizing enzyme, and the resulting glycolaldehyde is then oxidized to glycolic acid by an aldehyde oxidase (ALOD) (Figure 1).