啤酒酵母ECM25/YJL201W基因敲除对啤酒风味稳定性的影响

以pUG6为模板, 设计含有与ECM25基因两侧序列同源的长引物, 构建了带有卡那抗性基因(kanMX)破坏盒, 转化啤酒酵母G-03, 获得一株G-03/a转化菌, 遗传稳定性良好, 测序结果证实ECM25基因敲除是成功的。有氧条件下11oC和28oC培养时转化菌G-03/a的胞外谷胱甘肽(GSH)分泌量在对数生长期分别比原菌高21.4%和14.7%。在锥形瓶中连续发酵4代后, 与原菌株相比, 转化菌G-03/a发酵液、成品酒中GSH含量分别提高32.1%和13.8%, 发酵液和成品啤酒SI系数分别提高7.7%和5.3%, 成品啤酒RSV值提高45.0%。EBC管发酵6 d后, 与原菌株相比, 转化菌G-03/a发酵液中GSH含量提高34.0%。转化菌G-03/a与G-03所酿制成品啤酒的常规指标没有显著差别。表明G-03/a是一株具有抗老化能力的优良啤酒酵母, 能够提高啤酒的风味稳定性。

Effects of Knockout ECM25/YJL201W Gene in Brewing Yeast on Beer Flavor Stability

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 11oC and 28oC, 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.