Kohyama Erina, Dohi Mizuho, Yoshimura Akihiro, Yoshida Toyokazu, Nagasawa Toru
Gifu Prefectural Research Institute for Bioengineering, Kamihachiya, Minokamo, Gifu, Japan.
Appl Microbiol Biotechnol. 2007 Mar;74(4):829-35. doi: 10.1007/s00253-006-0738-2. Epub 2006 Nov 29.
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.
涉及产生腈水合酶和酰胺酶的微生物的串联转化过程在含乙腈废物的处理中具有应用潜力。在该过程中，与腈水合酶催化的乙腈水合步骤相比，酰胺酶催化的乙酰胺水解步骤非常缓慢，并且在所得溶液中会残留少量乙酰胺。本研究旨在提高乙酰胺水解步骤的效率。新获得了一种产生酰胺酶的微生物，红球菌属S13 - 4，使用该微生物能够快速降解乙酰胺。尽管仍检测到残留的乙酰胺，但在使用红球菌属S13 - 4细胞进行乙酰胺水解反应后，通过添加阳离子/阴离子混合离子交换树脂或氢氧化钙成功降低了残留量。该结果表明乙酰胺水解和乙酰胺形成处于平衡状态。用高浓度乙酸铵培养红球菌属S13 - 4细胞会产生乙酰胺。从红球菌属S13 - 4纯化得到的酰胺酶显示出乙酰胺形成活性（比活性为30.6 U/mg蛋白质）。这表明酰胺酶催化的酰胺形成可能导致乙腈转化过程中乙酰胺的残留。
