一株耐酸乳杆菌Lactobacillus acetotolerans FBKL1.0204的筛选鉴定及耐酸、产酸特性

Screening,identification and characterization of acid tolerant Lactobacillus acetotolerans FBKL1.0204

耐酸乳杆菌是浓香型白酒窖池发酵中后期酒醅中的优势菌,此时酒醅酸性较强。采用传统分离纯化法分离酒醅中细菌,经形态学特征和生理生化特性分析,并结合16S rDNA基因序列同源性分析和管家基因pheS和rpoA序列同源性分析及耐酸性筛选,分离鉴定出1株耐酸乳杆菌(Lactobacillus acetotolerans)FBKL1.0204。采用比浊法、电极电位法和高效液相色谱法测定菌株在不同酸胁迫下的生物量、pH和有机酸的变化。耐酸特性研究表明,在乳酸、乙酸和盐酸酸化的酸性发酵环境中,FBKL1.0204能耐受pH 4的酸性环境,极端生存pH值为3;产酸特性研究表明,FBKL1.0204为异型乳酸发酵,主要代谢生成乳酸和乙酸,最终使发酵液pH值降至3.5左右,在乙酸调节pH值为6的MRS培养基中,其代谢生成乳酸和乙酸含量最高,分别为(28.32±0.54)g/L和(2.73±0.52)g/L。由此可见,FBKL1.0204具有优良的耐酸和产酸特性,有利于其在白酒酿造过程中生长繁殖并丰富白酒风味。

Lactobacillus acetotolerans is the dominant bacteria in the middle and late fermentation in the pits of Luzhou-flavor Baijiu,which produces excessive acids and makes strong acidity of fermented grains.A strain FKL1.0204 in fermented grains was isolated and identified by morphological characteristics,physiological and biochemical characteristics,16 S rDNA gene sequence analysis,pheS and rpoA gene sequence analysis and acid tolerance screening.It was identified as Lactobacillus acetotolerans.Strain FKL1.0204 could withstand the acidic environment of pH 4,and the extreme survival pH was 3.The study of acid production characteristics showed that it was hetero-lactic acid fermentation,which mainly metabolized lactic acid and acetic acid,and finally lowers the pH of fermentation liquid to about 3.5.The contents of lactic acid and acetic acid were the highest in the MRS medium under pH 6(modified by acetic acid),(28.32±0.54)g/L and(2.73±0.52)g/L respectively.