1,2-Diazole and 2,2,2-Trifluoroethanol and Their Regulatory Effects on Ethanol and Lactic Acid Formation in the Living Culture of Rhizopus oryzae

Abstract

In heterofermentation of Rhizopus oryzae, ethanol is the major byproduct which reduces the production of a desired product, an optically pure L-lactic acid. To improve lactic acid production, regulating the alcohol fermentative pathway to limit ethanol production has been done by various techniques. In vitro study on alcohol dehydrogenase (ADH) inhibition in several organisms showed that 1,2-diazole and 2,2,2-trifluoroethanol were competitively bound at the active sites that eventually limited ethanol production. In this study, 1,2-diazole and 2,2,2-trifluoroethanol were present during fermentation of R. oryzae. It was found that both 1,2-diazole and 2,2,2-trifluoroethanol not only strongly affected ethanol formation but they also indirectly regulated lactate production as observed by the decreasing affinity for glucose flux toward lactate and ethanol production. The increase in both ethanol and lactate formation rates revealed 1,2-diazole and 2,2,2-trifluoroethanol not only regulated the reversible redox reaction by ADH, but they also caused the dynamic change in the conversion of all metabolites in the living R. oryzae in order to maintain the balanced flux for cellular growth and maintenance.