窖泥中降乳增己菌群的驯化及其在白酒发酵中的应用

Domestication of caproic acid-producing and lactic acid-utilizing microbe in the pit muds and its application in Baijiu fermentation

以浓香型白酒窖泥作为出发菌群,高乳酸盐浓度模拟黄水为载体,在自行设计的生物反应器中构建以乳酸转化为己酸为目的的反应体系。经不同操作条件培养相同时间后发现在37℃培养温度,进料pH值为5.5~6.0,乳酸进料质量浓度为40 g/L,活性炭和改性聚氨酯海绵填充反应容器时,该反应体系降乳增己功能明显加强。对比驯化前后,菌群结构发生显著变化,该体系发酵液中的微生物较窖泥出发菌群的微生物群落多样性显著降低,且与产己酸和降乳酸相关的Clostriduim属占主要优势,参与降解氨基酸的Aminobacterium属显著增多。将上述培养液运用于白酒发酵,常规发酵为对照,结果表明,在白酒发酵不同阶段加入强化黄水,原酒中的己酸乙酯含量均有不同程度的提高。在发酵初始加入强化黄水后的原酒中己酸乙酯含量达561.9 mg/L,相比对照组提高330.9%;发酵7 d后添加强化黄水的原酒与对照组相比己酸乙酯增加154.6%的同时乳酸乙酯下降9.8%,比例合宜。该研究证实了驯化窖泥菌群并将其运用于白酒发酵达到降乳增己的效果现实可行,对改善白酒风味提高品质具有积极意义。

A reaction system for converting lactic acid to caproic acid in a self-designed bioreactor was constructed,in this system,microbe in the pit mud of strong aroma Baijiu(Chinese liquor) was selected as the starting bacteria,and yellow water with high lactate acid concentration was used as the carrier.The optimum culture conditions were 40.0 g/L of lactic acid,at 37℃ and pH 5.5-6.0,in these conditions,the function of caproic acid-producing and lactic acid-utilizing was strengthened when the bioreactor was filled with activated carbon and modified polyurethane sponge.Results showed that the species diversities in the fermentation broth of the bioreactors were lower than those in pit muds,which was accompanied by the obvious changes in composition of dominant microbe.The dominant prokaryotes in the fermentation broth of the reactors were the Firmicute Clostridium related to caproic acid production and lactic acid reduction.And the Aminobacterium genus involved in the degradation of amino acids increased significantly.The ethyl caproate content in the original liquor were higher than that in conventional liquor fermentation when enhanced yellow water was added in different stages of Baijiu fermentation.When enhanced yellow water was added at the beginning of fermentation,the ethyl caproate content was 561.9 mg/L,which was 330.9% higher than that of the control group.After 7 days of fermentation,the ethyl caproate content increased by 154.6% and the ethyl lactate content decreased by 9.8%.In this study,domestication of pit mud bacteria and applying them to Baijiu fermentation were confirmed useful to increase ethyl caproate content while decreasing ethyl lactate content in production of strong aroma Baijiu,which is of positive significance to improve liquor flavor and quality.