植物源益生乳酸菌的筛选及其特性

为筛选具有益生特性的植物源乳酸菌，以传统发酵蔬菜中分离的1 000 株乳酸菌为出发菌株，进行了耐酸性、耐胆盐能力、抑菌性、体外抗氧化能力、药敏性、溶血性和氨基酸脱羧酶活性等特性研究，并对筛选菌株进行了16S rDNA 鉴定。经pH 3.0 MRS培养得乳酸菌82 株，再经pH 2.5 MRS培养得乳酸菌49 株；49 株菌经0.3%胆盐测试，均具有耐胆盐能力；根据镜检形态结合发酵植物源的不同从中挑选19 株乳酸菌进行药敏性、溶血性、抑菌性、氨基酸脱羧酶活性和1,1-二苯基-2-三硝基苯肼自由基清除实验。结果表明，19 株菌对所选20 种抗生素多数表现敏感，其中4 株菌对20 种抗生素都较敏感；19 株菌对供试致病菌都有不同程度抑制能力且都无溶血性；经氨基酸脱羧酶活性试剂盒结合聚合酶链式反应扩增检测表明，19 株菌无产生物胺的潜在威胁；有5 株菌体外抗氧化能力高于40%。可见19 株菌均具有益生菌的基本特性。经16S rDNA鉴定，7 株为发酵乳杆菌、6 株为植物乳杆菌，嫩江杆菌、戊糖片球菌、利莫西杆菌、戊糖乳杆菌、屎肠球菌、短乳杆菌分别各1 株。

Screening and Characterization of Plant-derived Probiotic Lactic Acid Bacteria

To select plant-derived lactic acid bacteria with probiotic characteristics, 1 000 strains of lactic acid bacteria (LAB) isolated from traditional fermented vegetables were evaluated for acid resistance, bile salt tolerance, bacteriostasis, in vitro antioxidant capacity, drug susceptibility, hemolytic activity and amino acid decarboxylase activity. Furthermore, the selected strains were identified by 16S rDNA gene sequencing. Totally 82 LAB strains were obtained by culturing in MRS medium at pH 3.0, and out of these, 49 strains were selected by culturing in MRS medium with pH 2.5, all of which were tolerant to 0.3% bile salt. Nineteen of the 49 strains were further selected based on their microscopic morphology and plant sources to evaluate their drug sensitivity, hemolytic activity, bacteriostatic effect, amino acid decarboxylase activity and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. Results showed that the 19 strains were susceptible to most of the 20 antibiotics tested with four of them being susceptible to all the antibiotics. All of the 19 strains had inhibitory activity against the tested pathogenic?bacteria?and had no hemolytic activity. As determined using a commercial amino acid decarboxylase activity kit and polymerase chain reaction (PCR), the 19 strains had no potential risk of producing bioamine, and the in vitro antioxidant capacity of five of these strains was higher than 40%, suggesting the 19 strains have probiotic properties. The results of identification showed that the 19 strains contained seven strains of Lactobacillus fermentorum, six strains of Lactobacillus plantarum, and one strain of Bacillus eneniensis, one strain of Lactococcus pentosus, one strain of Limoxibacter, one strain of Lactobacillus pentosus, one strain of Enterococcus faecium and one strain of Lactobacillus brevis.