川西高原发酵牦牛乳中降解亚硝酸盐乳酸菌的筛选与耐受性研究

以川西高原发酵牦牛乳中分离出的195株乳酸菌为研究对象,采用比色法测定其亚硝酸盐降解能力,从中筛选出亚硝酸盐降解能力极强的菌株。将这些优势菌株分别在人工胃液、人工肠液、胆盐和高盐4个模拟人工胃肠道消化环境中进行培养,测其耐受力。结果表明:这195株乳酸菌亚硝酸盐降解率范围为35.79%~96.51%,其中降解率在80%~90%的菌株占54.87%,仅有1.54%的菌株亚硝酸盐降解率在50%以下,有3株亚硝酸盐降解能力极强的菌株(降解率大于95%)。这3株菌在人工胃液中的活菌数随培养时间的延长而减少,培养3 h后,菌株5、26、150在pH5.5时的活菌数分别为3.7、3.6、4.1×10⁸ CFU/mL;在人工肠液中培养4 h后,菌株5、26、150的活菌数分别为4.3、6.8、5.3×10⁸ CFU/mL;在不同胆盐梯度的培养基中培养24 h后,3株菌的活菌数随胆盐浓度增大而减少,且均保持在10⁸ CFU/mL以上;在高盐环境中培养24 h后的活菌数随盐质量浓度的增加而降低,活菌数均在10⁸ CFU/mL以上。结论:川西高原发酵牦牛乳中分离出的195株乳酸菌降解亚硝酸盐的能力存在较大差异,其中降解亚硝酸盐能力极强的菌株对体外模拟消化环境具有较好的耐受力,为其在医药,食品和生物领域的应用提供了理论依据。

Screening and Tolerance of Degrading Nitrite-Lactant Bacteria in Fermented Yak Milk of Western Sichuan Plateau

In this paper,195 strains of lactic acid bacteria isolated from the yak milk from the western Sichuan Plateau were used as the research object. The nitrite degradation ability was determined by colorimetric method,and the strain with strong nitrite degradation ability was screened out. These dominant strains were cultured in artificial gastric juice,artificial intestinal juice,artificial bile and high salt in four simulated artificial gastrointestinal digestive environments,and their tolerance was measured.The results showed that the degradation rate of 195 lactic acid bacteria nitrite ranged from 35.79% to 96.51%,among which the strain with degradation rate of 80%~90% accounted for 54.87%,and only 1.54% of the strains had nitrite degradation rate below 50%. There were 3 strains with strong nitrite degradation ability(degradation rates were more than 95%). The viable counts of these three strains in artificial gastric juice decreased with the prolongation of culture time. After 3 h of culture,the viable counts of strains 5,26 and 150 at pH5.5 were 3.7,3.6,4.1×108 CFU/mL. After 4 h of culture in artificial intestinal juice,the viable counts of strains 5,26,and 150 were 4.3,6.8,and 5.3×108 CFU/mL,respectively. After cultured for 24 h in different bile salt gradient medium,the number of viable bacteria of the 3 strains decreased with the increase of bile salt concentration,and remained above 108 CFU/mL. The number of viable bacteria after 24 h culture in high salt environment decreased with the increase of salt concentration,and the number of viable bacteria was 108 CFU/mL or more. Conclusion:The ability of 195 strains of lactic acid bacteria isolated from traditional fermented yak milk in western Sichuan Plateau to degrade nitrite is quite different. The strain with strong nitrite degradation ability has good tolerance to in vitro simulated digestion environment. It provides a theoretical basis for applications in the pharmaceutical,food and biological fields.