蒙古族奶嚼口与下层凝乳中乳酸菌的筛选和比较研究

该研究以蒙古族奶嚼口和下层凝乳为原料，对乳酸菌进行计数和分离，通过产酸凝乳、耐胆盐实验及基因分析筛选并鉴定优良发酵菌株。结果表明，奶嚼口和下层凝乳中乳酸菌活菌数为（12.60±0.78）lg（CFU/mL）和（12.31±0.35）lg（CFU/mL）；分离获得的200株乳酸菌中有19株产酸凝乳能力较好，其中12株来源于奶嚼口，7株来自下层凝乳；在0.3 g/L和0.6 g/L胆盐环境中，奶嚼口中筛选出的乳酸菌具有更强的胆盐耐受性；奶嚼口筛选出11株乳酸乳球菌（Lactococcus lactis）和1株屎肠球菌（Enterococcus faecium）；下层凝乳筛选出的7株均为乳酸乳球菌。奶嚼口和下层凝乳中乳酸菌活菌数及种属并无明显差异，奶嚼口中分离的具有产酸凝乳能力的乳酸菌多于下层凝乳中所筛选的菌株，并有较强的胆盐耐受性。

Screening and comparison of lactic acid bacteria in Mongolian milk chew and lower curd

In this study, using Mongolian milk chew and the lower curd as raw materials, lactic acid bacteria were isolated and counted, and excellent fermentation strains were screened and identified by acid production and milk curdling assay as well as bile salt tolerance test and gene analysis. The results showed that the viable counts of lactic acid bacteria in the Mongolian milk chew and the lower curd were (12.60±0.78) lg(CFU/ml) and (12.31±0.35) lg(CFU/ml), respectively. A total of 19 strains of lactic acid bacteria with good capacity of acid producing and curdling forming were screened in the 200 isolated lactic acid bacteria, including 12 strains from the milk chew and 7 strains from the lower curd. The bile salt tolerance tests showed that the lactic acid bacteria screened from the milk chew had stronger tolerance in the environments of 0.3 g/L and 0.6 g/L bile salt. At last, 11 Lactococcus lactis and 1 Enterococcus faecium were screened from the milk chew. All the lactic acid bacteria from the lower curd were L. lactis. The counts and species of lactic acid bacteria in the Mongolian milk chew and lower curd had no significant difference. The counts of lactic acid bacteria with the capacity of acid production and milk curdling from the milk chew samples were greater than that in the lower curd, and had a stronger tolerance to bile salt.