清香型小曲白酒酒醅中乳酸菌的筛选鉴定及其发酵特性研究

该研究采用传统分离方法从不同季节清香型小曲白酒酒醅中分离乳酸菌，通过形态及分子生物学技术对其进行菌种鉴定，并探究其发酵特性。结果表明，共分离纯化出225株乳酸菌，经鉴定，归属于3属15种。通过高粱汁培养基初筛、固态发酵小试实验复筛，得到两株增酯降杂效果较好的乳酸菌，分别为纳格里乳杆菌（Lactobacillus nagelii）X29和布氏乳杆菌（Lactobacillus buchneri）X9。将强化乳酸菌X29和X9麸皮种加入桂花曲，最佳添加量为20%，此添加量下酒样中乙酸乙酯含量分别提升32.84%和16.79%，乳酸乙酯含量分别提升37.38%和36.44%，正丙醇含量分别降低2.61%和5.40%，杂醇油含量分别降低21.33%和26.71%。乳酸菌强化麸皮种糖化前加入能明显提升酒体中乙酸乙酯含量；糖化后加入则对乳酸乙酯含量和出酒率提升效果明显；延长发酵时间也可提升乙酸乙酯和乳酸乙酯含量。

Screening,identification and fermentation characteristics of lactic acid bacteria in fermented grains of light-flavor Xiaoqu Baijiu

The lactic acid bacteria strains were isolated from the fermented grains of light-flavor (Qingxiangxing) Xiaoqu Baijiu in different seasons by traditional separation method, identified by morphological and molecular biology techniques, and their fermentation characteristics were explored. The results showed that a total of 225 strains of lactic acid bacteria were isolated and purified, belonging to 3 genera and 15 species after identification. Two strains of lactic acid bacteria with better effect of increasing esters and reducing fusel oil content were obtained by primary screening of sorghum juice medium and secondary screening of sorghum solid-state fermentation, which were Lactobacillus nagelii X29 and Lactobacillus buchneri X9, respectively. The fortified bran seeds with lactic acid bacteria X29 and X9 were added to Guihuaqu, respectively, and the optimum addition was 20%. Under the optimal addition, the content of ethyl acetate in Baijiu samples increased by 32.84% and 16.79%, the content of ethyl lactate increased by 37.38% and 36.44%, the content of n-propanol reduced by 2.61% and 5.40%, and the content of fusel oil reduced by 21.33% and 26.71%, respectively. The addition of fortified bran seeds with lactic acid bacteria before saccharification could significantly increase the ethyl acetate content in the liquor body, the addition after saccharification could significantly improve the ethyl lactate content and liquor yield, and prolonging the fermentation time could also increase the ethyl acetate and ethyl lactate content.