H^+-ATPase弱化菌株的筛选及其应激性研究

Derivation of H^+-ATPase-defective mutant from Lactobacillus delbru-eckii subsp.bulgaricus KLDS1.9201 and its stress response

利用新霉素作为筛选压力,筛选H+-ATPase缺陷的德氏乳杆菌保加利亚亚种自发突变株,筛选出一株突变菌株,命名为KLDS1.9201-11。比较亲本菌株KLDS1.9201与突变菌株KLDS1.9201-11的生长情况,发现KLDS1.9201-11的生长活力较亲本菌株差且产酸能力弱;在pH 3.0的MRS液体培养基中经过3 h酸应激后,亲本菌株和突变菌株的活菌数分别降低86.98%和99.98%,酶活分别降低13.33%和21.15%;在冻干后,亲本菌株和突变菌株的活菌数分别降低76.71%和4.88%,亲本菌株的酶活降低4.27%,而突变菌株的酶活上升29.71%。结果表明,突变菌株较亲本菌株具有更强的酸敏感性和冷适应性,可以用于弱后酸化酸奶发酵剂的制备。

One spontaneous neomycin mutant strain named KLDS1.9201-11 was obtained from Lactobacillus delbrueckii subsp, bulgaricus KLDS1.9201, which showed the reduced H＋-ATPase activity. Compared with parent strain, the mutant strain had lower growth rate and acid yield ability. The acid tolerance of the two strains were compared by using three-hour-exposure process to acidic conditions with pH 3.0, results showed that the viable count of the parent strain and mutant strain reduced by 86.98% and 99.98%, separately, and the membrane-bound H＋-ATPase activities of the parent strain and mutant strain reduced by 13.33% and 21.15%, respectively. The freeze-drying test showed that the viable count of the parent strain and mutant strain reduced by 76.71% and 4.88%, respectively, and the membrane-bound H＋-ATPase activities of the parent strain reduced by 4.27%, while which of the mutant strain increased by 29.71%. In conclusion, compared to the parent strain, the mutant strain had higher sensitivity to acid and cold tolerance ability, which could be used to make the starter culture with low-postacidification ability.