Remaining acetamide in acetonitrile degradation using nitrile hydratase- and amidase-producing microorganisms |
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Authors: | Erina Kohyama Mizuho Dohi Akihiro Yoshimura Toyokazu Yoshida Toru Nagasawa |
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Institution: | (1) Gifu Prefectural Research Institute for Bioengineering, Kamihachiya, Hachiya-cho, Minokamo, Gifu 505-0004, Japan;(2) Department of Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan |
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Abstract: | The tandem conversion process involving nitrile hydratase- and amidase-producing microorganisms has potential for use in the
treatment of acetonitrile-containing wastes. In that process, the acetamide hydrolysis step catalyzed by amidase is very slow
compared with the acetonitrile hydration step catalyzed by nitrile hydratase, and a small amount of acetamide remains in the
resulting solution. This study aimed to improve the efficiency of the acetamide hydrolysis step. An amidase-producing microorganism,
Rhodococcus sp. S13-4, was newly obtained, whose use enabled rapid acetamide degradation. Though residual acetamide was still detected,
it was successfully reduced by the addition of cation/anion mixed ion exchange resin or calcium hydroxide after the acetamide
hydrolysis reaction using Rhodococcus sp. S13-4 cells. This result implies that acetamide hydrolysis and acetamide formation are in equilibrium. The incubation
of Rhodococcus sp. S13-4 cells with high concentrations of ammonium acetate produced acetamide. The purified amidase from Rhodococcus sp. S13-4 revealed the acetamide formation activity (specific activity of 30.6 U/mg protein). This suggests that the amidase-catalyzed
amide formation may cause the remaining of acetamide in the acetonitrile conversion process. |
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