Screening And Evaluating Of Lactic Acid Bacteria With Improving Intestinal Function From Traditional Fermented Yak Yogurt

Traditional fermented yak yogurt is one of the traditional characteristics of food in the Qinghai-Tibet plateau,China.It contained rich lactic acid bacteria resources after long-term natural selection and domestication.However,the precious lactic acid bacteria resources in traditional fermented yak yogurt were gradually disappearing,because the traditional production process has been replaced gradually with the new production process.In this study,we firstly focused on the collection lactic acid bacteria resources and the resistance screening of its Lactobacillus from traditional fermented yak yogurt of Hongyuan,Sichuan Province.Then,the best resistance of Lactobacillus was determined.Finally,based on the best resistance Lactobacillus,we evaluated its prevention effect to colitis and constipation.Therefore,this work was foundation for the excavation,preservation and its functional characteristics of lactic acid bacteria resources in traditional fermented yak yogurt.As follows were experiment methods and results.(1)Screening and resistance evaluation of lactic acid bacteria from traditional fermented yak yogurtBased on pure culture technology,we screened lactic acid bacteria from traditional fermented yak yogurt,and analysed the genus of isolated strains by 16 S r DNA sequence and phylogenetic tree.Then,we did the tolerance experiment of p H 3.0 artificial gastric juice and 0.3% bile to determine the Lactobacillus with the best resistance ability.The results showed that 43 strains were isolated from samples,and among these,8 strains was Lactobacillus casei,5 strains was Lactobacillus fermentum,4 strains was Lactobacillus plantarum,9 strains was Enterococcus durans,7 strains was Enterococcus faecium,4 strains was Leuconostoc mesenteroides subsp.mesenteroides,3 strains was Lactococcus lactis subsp.lactis,2 strains was Lactococcus lactis subsp.cremoris and 1 strains was Leuconostoc pseudomesenteroides.The analysis results of 16 S r DNA sequence and phylogenetic tree were consistent,and the dominant strains were Enterococcus durans,Lactobacillus casei and Enterococcus faecium in traditional fermented yak yogurt.In addition,the results of tolerance experiment shown that strain number MRSHY12-3 had the best resistance ability.Its survival rates were 103.73% in p H 3.0 artificial gastric juice and growth efficiency was 21.62% in 0.3% bile.Because of the analysis results of genus and collection sites,we renamed it Lactobacillus fermentum HY01.(2)Prevent effects of Lactobacillus fermentum HY01 to colitisIn order to evaluate the prevent effects of Lactobacillus fermentum HY01 to colitis,Lavaging different concentrations of Lactobacillus fermentum HY01 to DSS induced colitis mice(low concentration of 109 CFU/kg·BW,high concentration of 1010 CFU/kg·BW),and choicing colon length,the ratio of colon weight to its length,colon pathological changes,the levels of proinflammatory factor IL-6,IL-12,IFN-? and TNF? in serum,and the protein levels of I?B?,NF-?B p65,i NOS and COX-2 as evaluating indexes.The results showed that Lactobacillus fermentum HY01 had a significant anti-inflammatory effect.Compared to model group,It can effectively alleviate the colon length shorten,reduce the ratio of colon weight to its length,reduce edema,inflammatory cells infiltration and colon mucosa injury and significantly reduce the levels of proinflammatory factor IL-6,IL-12,IFN-? and TNF?.Furthermore,Lactobacillus fermentum HY01 can also prevent I?B? degradation,so which can inhibit NF-?B p65 phosphorylation cascades and reduce the protein levels of i NOS?COX-2.However,prevent effects of Lactobacillus fermentum HY01 to colitis was different at different concentrations,the prevent effects of high concentration was the most notable in all evaluating indexes to DSS induced colitis mice.(3)Prevent effects of Lactobacillus fermentum HY01 to constipationIn order to evaluate the prevention effect of Lactobacillus fermentum HY01 to constipation,Lavaging different concentrations of Lactobacillus fermentum HY01 to DSS induced colitis mice(low concentration of 108 CFU/kg·BW,high concentration of 109 CFU/kg·BW),and choicing constipation mice weight,the water content of defecation,gastrointestinal transit,the time to the first black stool defecation,small intestine pathology observation and the levels of MTL,GT,ET,Ach E,SP,SST and VIP in serum as evaluating indexes.The result showed that that Lactobacillus fermentum HY01 had a significant prevent effects.Compared to model group,Lactobacillus fermentum HY01 can significantly increase the water content of defecation in constipation mice,improve gastrointestinal transit,shorten the time of the first black stool defecation,reduce the damage of small intestinal villus.In addition,Lactobacillus fermentum HY01 can improve the levels of MTL,GT,ET,Ach E,SP,and VIP,and reduce the level of SST in serum.However,prevent effects of Lactobacillus fermentum HY01 to constipation was different at different concentrations,the prevent effects of high concentration was the most notable in all evaluating indexes to carbon-induced constipation mice.In conclusion,traditional fermented yak yogurt had rich lactic acid bacteria resources,and we also found that Lactobacillus fermentum HY01 had significant prevent effect to colitis and constipation.It can laid a good foundation for further researching of functional lactic acid bacteria to colitis and constipation.