低能N+注入诱变选育弱后酸化保加利亚乳杆菌

为获得弱后酸化保加利亚乳杆菌（Lactobacillus bulgaricus），采用低能N+注入技术对保加利亚乳杆菌DL1进行诱变，经中间培养后用青霉素进行筛选。结果表明，在注入能量为25 keV、注入剂量为1.5×1015 ions/cm2的条件下进行诱变，并用2.0 mg/mL青霉素处理2 h后，通过筛选最终得到一株后酸化较弱的突变菌株DL1-3。与出发菌株DL1相比，突变菌株DL1-3在25 ℃条件下贮藏后，后酸化程度降低18.8%，且在42 ℃条件下发酵脱脂乳的产酸能力差异较小，并可稳定遗传。

Mutation breeding of weak post-acidification Lactobacillus bulgaricus by low energy nitrogen ion implantation

To obtain the yogurt starter strain with weak post-acidification capacity, Lactobacillus bulgaricus DL1 was treated by low energy nitrogen ion implantation, and screened with penicillin after intermediate culture. The results showed that the strain was mutated under the condition of energy 25 keV and implantation dose 1.5×1015 ions/cm2, and treated with 2.0 mg/ml penicillin for 2 h, and finally a mutant strain DL1-3 with weak post-acidification was obtained by screening. Compared with the original strain DL1, the post-acidification degree of mutant strain DL1-3 decreased by 18.8% when stored at 25 ℃. The difference in acid production capacities of skimmed milk fermented at 42 ℃ was small, and the mutant strain were genetically stable.