EVALUATION OF ELECTRON MEDIATORS FOR THE ELECTROMICROBIAL REDUCTION OF CHLOROPYRUVATE BY PROTEUS-VULGARIS CELLS

Different electron mediators were evaluated for the electromicrobial r eduction of chloropyruvate to chlorolactate. The reaction was catalyze d by a mediator-dependent D-lactate dehydrogenase in whole cells of Pr oteus vulgaris and yielded D-(S)-chlorolactate with high optical purit y (> 97% e.e.). The ideal mediator should favor a high rate in the enz ymatic reaction and a low rate in the nonenzymatic dehalogenation of t he substrate. The latter reaction causes the formation of pyruvate and subsequently lactate. Viologens as mediators provided better yields t han cobalt sepulchrate, safranine O, and an anthraquinone derivative. The best results were obtained with 1,1'-carbamoylmethylviologen as me diator. (C) 1997 by Elsevier Science Inc.