College of Bioengineering, Sichuan University of Science and Engineering, Yibin, Sichuan 644005, P.R. China.
Wuliangye Yibin Co., Ltd., Yibin, Sichuan 644000, P.R. China.
J Microbiol Biotechnol. 2023 Oct 28;33(10):1337-1350. doi: 10.4014/jmb.2304.04013. Epub 2023 Jun 26.
Caproic acid is a precursor substance for the synthesis of ethyl caproate, the main flavor substance of nongxiangxing baijiu liquor. In this study, GD1-1, a strain with high caproic acid concentration (3.86 g/l), was isolated from the storage pit mud of nongxiangxing baijiu for sequencing and analysis. The strain's genome was 3,840,048 bp in length with 4,050 open reading frames. In addition, virulence factor annotation analysis showed GD1-1 to be safe at the genetic level. However, the annotation results using the Kyoto Encyclopedia of Genes and Genomes Automatic Annotation Server predicted a deficiency in the strain's synthesis of alanine, methionine, and biotin. These results were confirmed by essential nutrient factor validation experiments. Furthermore, the optimized medium conditions for caproic acid concentration by strain GD1-1 were (g/l): glucose 30, NaCl 5, yeast extract 10, peptone 10, beef paste 10, sodium acetate 11, L-cysteine 0.6, biotin 0.004, starch 2, and 2.0% ethanol. The optimized fermentation conditions for caproic acid production by GD1-1 on a single-factor basis were: 5% inoculum volume, 35°C, pH 7, and 90% loading volume. Under optimal conditions, the caproic acid concentration of strain GD1-1 reached 5.42 g/l, which was 1.40 times higher than the initial concentration. GD1-1 could be further used in caproic acid production, NXXB pit mud strengthening and maintenance, and artificial pit mud preparation.
己酸是合成己酸乙酯的前体物质，己酸乙酯是浓香型白酒的主要风味物质。本研究从浓香型白酒窖泥中分离到一株己酸浓度（3.86g/L）较高的菌株 GD1-1 进行测序与分析。该菌株基因组全长 3840048bp，包含 4050 个开放阅读框。此外，毒力因子注释分析表明，GD1-1 在遗传水平上是安全的。但是，京都基因与基因组百科全书自动注释服务器的注释结果预测该菌株在合成丙氨酸、蛋氨酸和生物素方面存在缺陷。通过必需营养因子验证实验证实了这一结果。进一步优化了菌株 GD1-1 产己酸的培养基条件（g/L）为：葡萄糖 30、NaCl 5、酵母提取物 10、蛋白胨 10、牛肉膏 10、乙酸钠 11、L-半胱氨酸 0.6、生物素 0.004、淀粉 2.0%和 2.0%乙醇。在单因素条件下，菌株 GD1-1 发酵生产己酸的优化发酵条件为：接种量 5%、35℃、pH7、装液量 90%。在最优条件下，菌株 GD1-1 的己酸浓度达到 5.42g/L，比初始浓度提高了 1.40 倍。GD1-1 可进一步用于己酸生产、窖泥强化与维护以及人工窖泥的制备。
