罗伊氏粘液乳杆菌K07的生物学特性及其基因分析

从新疆昭苏县传统发酵乳酪中分离出2株罗伊氏粘液乳杆菌（编号K07、K08），对2株菌的生长和产酸性能、耐酸耐胆盐、模拟胃肠道的耐受、产罗伊氏菌素能力和抗氧化活性进行了评估；此外还测定了2株菌的抑菌性能并对K07菌株进行基因分析。结果表明，2株菌均在培养12 h后进入对数生长末期，发酵终点pH值为4.45。K07对酸、胆盐和模拟胃肠道的耐受及抗氧化能力强于K08。pH值2.50处理4 h，K07存活率为73.27%。0.15%胆盐胁迫下K07菌株OD600 nm 上升0.3个单位需5.50 h，模拟胃肠道试验K07的存活率为74.13%。两株菌的无细胞提取物抗氧化活性高于完整细胞，其中K07无细胞提取物对DPPH自由基和羟自由基的清除率为42.39%、15.69%，还原力17.96%。K07产罗伊氏菌素量为183.05 mmol/L显著高于K08，且K07抑菌性能较好，对白色念珠菌和无乳链球菌的抑菌圈直径为22.20 mm、18.26 mm。K07基因组全长1 950 440 bp，预测蛋白质编码基因2 067种，GC含量为38.69%。研究结果显示罗伊氏粘液乳杆菌K07具有良好的益生特性，为后续产业化应用提供理论依据。

Biological Characteristics of Limosilactobacillus reuteri K07 and Its Genetic Analysis

Two strains of Limosilactobacillus reuteri (K07, K08) were isolated from traditional fermented cheese of Zhaosu County, Xinjiang Province. The growth, acid production, acid tolerance, bile salt tolerance, tolerance to simulated gastrointestinal tract, reuterin-producing capacity and antioxidant activity of the two strains were evaluated. In addition, the bacteriostatic performance of two strains was determined and genetic analysis of the K07 strain was performed. The results showed that both strains entered the late logarithmic growth phase after 12 hours of culture, and the endpoint pH of fermentation was 4.45. K07 exhibited stronger tolerance to acid, bile salt and the simulated gastrointestinal tract as well as higher antioxidant ability than K08. The survival rate of K07 was 73.27% after the treatment at pH 2.50 for 4 h. For the K07 strain, it took 5.50 hours for the OD600 nm to increase by 0.3 units under the stress of 0.15% bile salt. The survival rate of K07 in the simulated gastrointestinal test was 74.13%. The antioxidant activities of the cell-free extracts of the two strains were higher than those of the intact cells, with the scavenging rates of the cell free extracts of K07 for DPPH free radicals and hydroxyl free radicals were 42.39% and 15.69%, respectively. with the reducing power being17.96%. The amount of reuterin produced by K07 was 183.05 mmol/L, which was significantly higher than that of K08. Also, K07 exhibited better antimicrobial performance. The diameters of inhibition zones for Candida albicans and Streptococcus agalactiae were 22.20 mm and 18.26 mm, respectively. The full length of K07 genome was 1 950 440 bp, with 2067 predicted protein coding genes. The content of GC was 38.69%. The research results showed that Limosilactobacillus reuteri K07 had good probiotic properties, which provides a theoretical basis for subsequent industrial applications.