耐酸耐胆盐乳酸菌的鉴定及筛选

从自然发酵的酸奶中分离出2 株细菌，经16S rDNA分子鉴定为Lactobacillus plantarum SN1和Lactobacillusrhamnosus SN6，并对其生长曲线、产酸速率、耐酸耐胆盐能力进行了研究。L. plantarum SN1和L. rhamnosus SN6在2 h后进入对数期，16 h后达到稳定期，其OD600 nm值分别为8.47、7.43。L. plantarum SN1和L. rhamnosus SN6的产酸速率较快，pH值在8 h后就降到了4.2以下，48 h后降到3.3左右。L. plantarum SN1和L. rhamnosus SN6在pH 4的培养基培养16 h后，其相对OD600 nm值分别为49.29%、47.14%，具有较强的耐酸能力。L. plantarum SN1和L. rhamnosus SN6在0.3 g/L胆盐质量浓度下培养16 h后，相对OD600 nm值分别为57.7%、69.48%；在0.6 g/L胆盐质量浓度下的相对OD600 nm值分别为48.22%、29.56%，具有较强的耐胆盐能力。结果表明：L. plantarum SN1和L. rhamnosus SN6是生长性能好、产酸能力强、耐酸耐胆盐的益生菌株。

Identification and Selection of Lactic Acid Bacteria Resistant to Acid and Bile Salt

Two strains of lactic acid bacteria were isolated from naturally fermented yogurt. The 16S rDNA sequence analysis
indicated that the two strains were Lactobacillus plantarum SN1 and Lactobacillus rhamnosus SN6. These strains were studied
for growth curve, acid production rate, acid and bile salt tolerance. Both of them reached a logarithmic growth phase after 2 h
and a stable period after 16 h with OD 600 nm values of 8.47 and 7.43, respectively. The pH value dropped to 4.2 at 8 h and 3.3
at 48 h. L. plantarum SN1 and L. rhamnosus SN6 had strong resistance to acid, and the relative OD 600 nm value was 49.29%
and 47.14% at pH 4.0 after 16 h of culture, respectively. After being cultured for 16 h at a bile salt concentration of 0.3 g/L,
the relative OD 600 nm values of L. plantarum SN1 and L. rhamnosus SN6 were 57.7% and 69.48%, respectively, compared
to 48.22% and 29.56% when the concentration of bile salt was 0.6 g/L. These results show that both L. plantarum SN1
and L. rhamnosus SN6 are probiotic strains with strong growth performance, acid production and tolerance to acid
and bile salt.