State Key Laboratory of Food Science and Technology, Key Laboratory of Industrial Biotechnology of Ministry of Education, Center of Brewing Science and Enzyme Technology, School of Biotechnology, Jiangnan University, No. 1800, Lihu Road, Wuxi, 214122, China.
Appl Biochem Biotechnol. 2013 Dec;171(8):2220-32. doi: 10.1007/s12010-013-0493-7. Epub 2013 Sep 14.
Rhodotorula mucilaginosa, producing the ethyl carbamate (EC)-degrading enzyme, urethanase, was newly isolated from the Chinese rice wine making process. It removed 80 % of EC when it was incubated with 5.0 g/L EC. It grew and stably produced urethanase, with pH ranging from 7.0 to 3.0. In addition, urethanase production by R. mucilaginosa was systematically optimized. Glucose, yeast extract, peptone, and inoculum size were selected with the Plackett-Burman design. They were further optimized via uniform design and determined to be 24.6 g/L, 2.5 g/L, 23.1 g/L, and 65.8 mL/500 mL, respectively. Urethanase activity reached 4,340.0 U/L in the optimal fermentation condition. Furthermore, cell immobilization of R. mucilaginosa in calcium alginate/chitosan was applied to improve cell resistance to environmental stresses. The immobilized cells removed 51.6 % of EC in commercial rice wine, which was 10 times more than that of the free cells. It indicated that the immobilized R. mucilaginosa was effective for degrading EC.
胶红酵母是一种新型的产氨基甲酸乙酯（EC）降解酶—尿烷酶的微生物，从中国米酒的酿造过程中分离得到。在 5.0g/L EC 浓度下培养时，它能去除 80%的 EC。其最适生长和产酶 pH 范围为 7.0-3.0。此外，还对胶红酵母产尿烷酶进行了系统优化。利用 Plackett-Burman 设计选择了葡萄糖、酵母提取物、蛋白胨和接种量作为影响因素，再通过均匀设计对其进一步优化，确定最佳浓度分别为 24.6g/L、2.5g/L、23.1g/L 和 65.8mL/500mL。在最佳发酵条件下，尿烷酶的酶活达到 4340.0U/L。进一步将胶红酵母细胞固定在海藻酸钠/壳聚糖中，以提高细胞对环境胁迫的抵抗力。固定化细胞在商业米酒中去除了 51.6%的 EC，是游离细胞的 10 倍。这表明固定化胶红酵母对 EC 的降解是有效的。
