高产酸及耐酸性干酪乳杆菌的诱变筛选

Screening high acid- producing and acid- resistant Lactobacillus casei strains

为筛选高产酸及耐酸的干酪乳杆菌菌株,以干酪乳杆菌LC2W为出发菌株,分别对其进行紫外(Ultraviolet,UV)、亚硝基胍(Nitrosoguanidine,NTG)和硫酸二乙酯(Diethyl sulfate,DES)诱变以及人工胃液处理。结果显示,通过0.3 g/L的亚硝基胍处理30 min和紫外线照射30 s后得到的诱变菌株LC2W-NTG-12,LC2W-UV-11表现出高产酸及耐酸性能。相同条件下,出发菌株LC2W和突变菌株LC2W-NTG-12,LC2W-UV-11经24 h发酵后的滴定酸度分别为76.6°T和112.7°T,98.2°T,突变菌株产酸能力分别提高了47.13%、28.20%。当用p H为1.5的酸液处理2 h后,出发菌株和诱变菌株LC2W-NTG-12,LC2W-UV-11的致死率分别为76.44%、52.06%、56.36%,诱变菌株耐酸能力分别提高了24.38%、20.08%。而用0.16%DES处理30 min得到的诱变菌株LC2W-DES-33发酵后的酸度仅比出发菌株提高了14.10%,诱变效果并不明显。说明亚硝基胍诱变可有效提高干酪乳杆菌的产酸及耐酸性能。

in order to screen a high acid-producing and acid-resistant strain, Lactobacillus casei LC2W was subjected by Ultraviolet （ UV）, Nitrosoguanidine （ NTG ）, Diethyl sulfate （DES） respectively, and then treated with simulated gastric fluid.The results showed that the mutation strain LC2W-NTG-12 and LC2W-UV-11 which were subjected by 0.3 g/L NTG for 30 min and UV treatment for 30 s exhibited high acid-producing and acid-resistant. In the same amount of inoculation,the acidity of the fermented by the parent＇ strain and mutation strain were 76.6 °T and 112.7°T,98.2°T after 24 h, respectively.The acid-production rate of mutation strain was improved 47.13%, 28.20%.In addition,when the strains were treated with the acid （pH = 1.5）, the mortality rate of parent stain and mutation strain were ？6.44% and 52.06% ,56.36% after 2 h, respectively.The acid-resistant rate of mutation strain was improved 24.38 % ,20.08 %.But the effect of mutation strain LC2W- DES-33 which was subjected by 0.16% DES for 30 min was not obvious.The acid-production rate of mutation strain was improved only 14.10% compared with the parent strain.This implied that NTG mutation can effectively improve the acid-producing and acid-resistant of the Lactobacillus casei LC2W.