Glucose metabolism and bioreduction of 2-butanone by Candida utilis studied by means of ion-exchange chromatography

The metabolism of glucose during cell growth was important for the production yield of the yeast mediated bioreduction of ketones. Thus, the choice of the very simple acyclic ketone 2-butanone as the substrate for Candida utilis can easily explain the effect of glucose metabolism on the enantioselective bioreduction mechanism of ketone. The glucose metabolism was extended by adding the sorbitol (polyol) pathway to the Embden-Meyerhoff pathway due to the existence of a NADP-specific polyol dehydrogenase in C. utilis. The metabolite, glycerol, was produced via the sorbitol pathway which could suppress the production of ethanol by the Embden-Meyerhoff pathway. The reaction mechanism of bioreduction showed that ethanol, an energy source of the bioreduction, must be oxidized to acetic acid to activate the oxidoreductase. The formation of acetic acid, therefore, can serve as a mark for the success of bioreduction. On the other hand, the unconsumed glucose and the less added 2-butanone indicated a negative effect for the bioreduction. Overall, the microbial biotransformation of 2-butanone to S-form 2-butanol studied by ion-exchange chromatography was successful.