| Lactobacillus plantarum ZDY2013 was a probiotic strain that tolerates gastrointestinal digestive environment and inhibits six common foodborne pathogens.It specifically metabolized monosaccharides,disaccharides and oligosaccharides and regulated intestinal microecological balance.Colitis was a chronic gastrointestinal tissue disease caused by high fat and low fiber diet,intestinal microflora disorder,intestinal immune dysregulation and genetic factors,which posed a great challenge to public health.To explore whether this strain combined with functional oligosaccharides to relieve colitis in vivo,based on the establishment of the in vivo specific identification method of L.plantarum ZDY2013,the interaction between L.plantarum ZDY2013 and Bacillus cerus HN001 and the improvement effect of L.plantarum ZDY2013 in combination with oligosaccharides on colitis in mice were evaluated by q-PCR,immunofluorescence staining and 16 S r RNA sequencing.The effects of functional oligosaccharides on the preparation characteristics of L.plantarum fermented milk were analyzed.The main research contents and results are as follows:The first chapter reviewed the probiotic functions of L.plantarum and functional oligosaccharides and their alleviating effects on intestinal inflammatory disease,summarized the pathogenesis of colitis and the research progress of synbiotics alleviating colitis.The second chapter established a method for specific identification of L.plantarum ZDY2013 in complex gut environment.Specific primers of L.plantarum ZDY2013 were designed based on bioinformatics methods.The sensitivity and accuracy of q-PCR method for the analysis of artificial mixed fecal samples were verified,and the colonization of L.plantarum ZDY2013 in the gastrointestinal tract of mice and its interaction with B.cereus HN001 were monitored.The results showed that the designed specific primers could be used for the analysis of complex stool samples.L.plantarum ZDY2013 was mainly enriched in the large intestine of mice after ingestion,and the interaction with B.cereus significantly promoted its colonization in large intestine(p<0.0001).The interaction of the two strains did not improve intestinal inflammation,liver and kidney damage caused by B.cereus.In third chapter,based on the method of specific identification of intestinal strains established in the previous chapter,the effect of L.plantarum ZDY2013 utilized isomaltooligosaccharide in intestinal fermentation to alleviate mice colitis in mice was studied.A DSS-induced colitis model in mice was established,and the remission effect of the combination of L.plantarum ZDY2013 and isomaltooligosaccharide on colitis was analyzed.The results showed that the combination of L.plantarum ZDY2013 and isomaltooligosaccharide significantly restored the body weight of colitis mice,decreased the DAI score,protected colonic mucosal injury and increased the expression of intestinal barrier related proteins(ZO-1,Claudin and MUC-2)(p<0.01),reduced the expression of pro-inflammatory cytokines in the colon(p<0.0001),and enhanced the host’s antioxidant function(p < 0.001).L.plantarum ZDY2013 utilized isomaltooligosaccharide in the intestinal tract,which significantly promoted its colonization and improved the level of SCFAs in the colon.The results of gut flora sequencing also proved that L.plantarum ZDY2013 and its combination with isomaltooligosaccharide enriched SCFAs-producing bacteria,and the treatment with isomaltooligosaccharide increased the abundance of probiotics such as Lactobacillus.All three treatments approached the gut flora of colitis to a healthy state.The fourth chapter further analyzed the application and development of L.plantarum ZDY2013 and functional oligosaccharides in the preparation of fermented milk.Xylooligosaccharide had excellent antioxidant activity and could be used to improve the quality of fermented milk.Firstly,the effects of isomalto and xylooligosaccharides and their compositions on the metabolism of L.plantarum ZDY2013 in vitro were analyzed.Secondly,the effects of different concentrations oligosaccharides and their compositions on the growth of L.plantarum ZDY2013 in fermented milk were investigated.Finally,the viable count,p H,water holding capacity,antioxidant activity and proteolytic activity of the fermented milk within 21 days of refrigeration were evaluated.The results showed that different oligosaccharides and their compositions promoted the growth of L.plantarum ZDY2013 and reduced the p H of the fermentation broth.The combined sugars of 1.5%,3.0% isomalto and xylooligosaccharides significantly increased the viable counts of L.plantarum ZDY2013 in fermented milk(p<0.001),reduce the p H of fermented milk.The addition of 1.5%oligosaccharides composition maintained the viable count,boosted the water holding capacity,antioxidant capacity and proteolytic capacity of fermented milk in cold storage period,and prolonged the shelf life of fermented milk.The fifth chapter summarized the colonization characteristics of L.plantarum ZDY2013 in gastrointestinal tract and its interaction with B.cereus,synergistic relieving effect of L.plantarum ZDY2013 and functional oligosaccharide on colitis in mice,and the improvement of functional oligosaccharides on fermented milk quality.Based on SCFASs,the molecular mechanism of L.plantarum ZDY2013 and functional oligosaccharide synergistic improvement of colitis was prospected.In summary,this thesis evaluated the colonization niche of L.plantarum ZDY2013 in the gastrointestinal tract of mice,and explored the alleviation of L.plantarum ZDY2013 by isomaltooligosaccharide fermentation in mice with colitis,and analyzed the effect of adding functional oligosaccharides on the quality of L.plantarum ZDY2013 fermented milk.The thesis provided an experimental basis for the development and application of probiotics and prebiotics in health care products,dairy products fields. |
