REDUCTION OF ACETOIN TO 2,3 BUTANEDIOL IN KLEBSIELLA PNEUMONIAE: A STEREOCHEMICAL MODEL AND KINETICS
Abstract
The fermentation of D-xylose by Klebsiella pneumoniae (ATCC 8724) produces a mixture of 2,3 butanediol stereoisomers. These isomers were separated by aqueous liquid chromatography and identified as meso and L(+) 2,3 butanediol, the former being the major product. A model is described for the conversion of acetoin isomers to 2,3 butanediol isomers by two acetoin reductases, D(-) acetoin reductase and L(+) acetoin reductase, and an acetoin racemase. The two reductases were isolated from K. pneumoniae and partially purified by DEAE-cellulose column chromatography. D(-) Acetoin reductase was found to catalyze the reduction of D(-) acetoin to meso 2,3 butanediol and L(+) acetoin reductase the reduction of L(+) acetoin to L(+) 2,3 butanediol. Both reactions are NADH-dependent. D(-) acetoin reductase was shown to follow an ordered Bi-Bi mechanism and its kinetic constants were determined by initial rate kinetic studies. The kinetic model was then numerically integrated and shown to predict the reaction time course up to 85% conversion over a 100 fold range in substrate concentration. The results obtained by initial rate kinetics were also compared to those obtained by using an integrated kinetic equation. Kinetic constants of L(+) acetoin reductase were obtained using an integrated rate equation for an ordered mechanism.
Degree
Ph.D.
Subject Area
Chemical engineering
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