Zhang Yixin, Li Qi, Shen Wei, Xie Yan, Gu Guoxian
The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China.
Sheng Wu Gong Cheng Xue Bao. 2008 Aug;24(8):1420-7.
The ECM25 deletion mutant of industrial brewing yeast, G03/a, was constructed by replacing the ECM25 gene with the kanMX gene. The transformant was verified to be genetically stable. The PCR analysis showed that ECM25 gene in the G-03/a was deleted. Under aerobic conditions of ll degrees C and 28 degrees C, compared with the host strain G-03, the excretive glutathione concentration of G-03/a increased by 21.4% and 14.7%, respectively. Strains G-03 and G-03/a were inoculated in flasks and cultivated continuously for 4 generations. Compared with the host strain G-03, the glutathione concentration in the main fermentation broth and final beer of strain G-03/a increased by 32.1% and 13.8%, the stability index (SI) increased by 7.7% and 5.3%, respectively, and the flavor resistance staling value (RSV value) in final beer increased by 45.0%. During EBC fermentation, the glutathione concentration in the main fermentation broth of strain G-03/a increased by 34.0%, compared with the host strain G-03. Furthermore, no significant difference in routine fermentation parameters was found. The strain G-03/a is proved to be an excellent anti-staling brewing yeast to improve beer flavor stability.
通过用kanMX基因替换工业酿造酵母的ECM25基因，构建了其缺失突变体G03/a。验证该转化体具有遗传稳定性。PCR分析表明G-03/a中的ECM25基因已缺失。在11℃和28℃的有氧条件下，与宿主菌株G-03相比，G-03/a的分泌型谷胱甘肽浓度分别提高了21.4%和14.7%。将菌株G-03和G-03/a接种到烧瓶中并连续培养4代。与宿主菌株G-03相比，菌株G-03/a的主发酵液和成品啤酒中的谷胱甘肽浓度分别提高了32.1%和13.8%，稳定指数（SI）分别提高了7.7%和5.3%，成品啤酒中的风味抗老化值（RSV值）提高了45.0%。在EBC发酵过程中，与宿主菌株G-03相比，菌株G-03/a的主发酵液中的谷胱甘肽浓度提高了34.0%。此外，常规发酵参数未发现显著差异。菌株G-03/a被证明是一种优良的抗老化酿造酵母，可提高啤酒风味稳定性。
