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d-Alanine production from dl-alanine by Candida maltosa with asymmetric degrading activity
Authors:Isao Umemura  Koji Yanagiya  Saburo Komatsubara  Tadashi Sato  Tetsuya Tosa
Affiliation:(1) Research Laboratory of Applied Biochemistry, Tanabe Seiyaku Co., Ltd. 16–89, Kashima-3-chome, 532 Yodogawa-ku, Osaka, Japan
Abstract:Summary To develop a practical process for d-alanine production from dl-alanine, we screened 107 yeasts for their asymmetric degrading activity against dl-alanine. Candida maltosa JCM1504 degraded the l-isomer ten times more rapidly than the d-isomer. The cells of this strain were used as a biocatalyst for eliminating the l-isomer. However, when the degradation reaction was conducted in the presence of a high concentration of dl-alanine, the pH of the reaction mixture was rapidly increased by the liberation of ammonia from l-alanine, and consequently the reaction stopped. This hindrance was overcome by controlling the pH value at 6.0 with H2SO4 during the reaction. Additionally, we found that the maximum rate of l-isomer degradation was obtained at 30° C and pH 6.0 under conditions of high aeration (1.0 vvm) and agitation (1200 rpm). Under the optimal conditions, the l-isomer of 200 g dl-alanine/l was completely degraded within 40 h and 90 g d-alanine/l remained in the reaction mixture. d-Alanine was easily isolated from the reaction mixture. The chemical and optical purity of the d-isomer product so obtained was 99.0% and 99.9% enantiomeric excess, respectively.Offprint requests to: I. Umemura
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