乳酸菌低温菌株的复合诱变选育

Selection for low temperature-resistant strain by composite mutagenesis of lactic acid bacteria

【目的】采用复合诱导的方法,选育出能在低温条件下性状稳定、生长良好且具有工业生产价值的低温乳酸菌菌株。【方法】使用紫外照射和亚硝基胍处理的方法对分离的Q1菌株进行诱变处理,将选育得到的低温菌株Q1-4-6与出发菌株Q1在15°C、20°C、37°C下,比较其生长速率、产酸量和糖降解量。【结果】从玛曲牧民自制酸奶中分离得到一株乳酸菌Q1,根据其形态学特征、生理生化特性,同时结合16SrDNA序列分析结果,将其鉴定为肠球菌属棉籽糖肠球菌(Enterococcus raffinosus)。经过多轮诱变选育出一株能在低温下良好生长、遗传性状稳定的菌株Q1-4-6,将出发菌株与诱变菌株在15°C、20°C比较其生长、产酸和糖降解量发现,诱变菌株均好于出发菌株。在37°C的自然条件下,诱变菌株和出发菌株的生长速率差异不大,但均略高于出发菌株。在15°C培养发现,诱变菌株生长速率、产酸量均高于购买菌株干酪乳杆菌(CL04)和嗜热链球菌(CL05)。【结论】通过UV+NTG复合诱变,最终选育出一株在低温下生长良好、遗传性状稳定的菌株Q1-4-6。

[Objective] Adopted a method of mixed induction, which can selected traits stable and growing well strains at low temperature, in order to get the low temperature-resistant strain with industrial value. [Methods] Mutagenized isolated Q1 by using ultraviolet irradiation and nitrosoguanidine treatment methods, put the strains Q1-4-6 and Q1 which al- ready selected under the 15 ℃, 20 ℃, 37 ℃, compare their growth rate, acid production and the amount of sugar degradation. [Results] Q1 was extracted in homemade yogurt by Maqu pastoralists, the strain was classified into Enterococcus raffinosus according to its morphol- ogy, the physiological and biochemical features and 16S rDNA sequence. After several rounds of mutation breeding, select a strain Q 1-4-6 that can grow well at low temperatures and genetic traits stable. Compared growth, the amount of acid and sugar degradation between the original strains and mutant strains, we found mutants were better than the original strains. At 37 ℃ natural conditions, there are rarely differences in growth rate between the original strains and mutants strains, but both of them are a little bit higher than the original strains. The acid amount and growth rate of Q1-4-6 are better than CL04 and CL05 under 15 ℃. [Conclusion] Through complex mutagenesis of UV＋NTG, eventually bred a strain Q1-4-6 that growing well at low temperatures with stable genetic traits.