Screening And Probiotic Characteristics Analysis Of Bifidobacteria With Relieving Constipation

Constipation is one of the common gastrointestinal symptoms,and the incidence of constipation significantly increases with age.Constipation plays a tremendous impact on the living quality of patients.Intestinal dysbacteriosis generally exists in constipated patients while the abundance of Bifidobacterium genus is remarkably decreased.Compared with other lactic acid bacteria,Bifidobacteria are more efficient in relieving constipation.Specifically,Bifidobacteria can elevate frequencies of defecation,decrease the fecal transit time,and soften the fecal form.Moreover,B.animalis subsp.lactis BB12 is studied deeply in relieving constipation.To develop new strains with constipation-reducing efficacy,the Bifidobacteria were screened by physiological characteristics in vitro and constipation mice models in vivo.Furthermore,the safety and probiotic characteristics of the strain were analysed from the genetic level.The main results are as follows:At first,the physiological characteristics of 12 human-residential Bifidobacteria were determined in vitro.The simulated gastrointestinal fluid tolerance,HT-29 cell adhesion,antibacterial activity and functional oligosaccharide utilization capacity of strains were measured.5 strains with the highest physiological characteristics were obtained by principal component analysis: B.breve CCFM670,B.bifidum CCFM16,B.adolescentis CCFM744,B.longum subsp.infantis CCFM689 and B.longum subsp.longum CCFM760.These strains represented outstanding performance in gastrointestinal fluids tolerance,antibacterial capacity and oligosaccharide utilization ability,but showed strain specificity in adhesion characteristics.Then,the 5 Bifidobacteria were investigated for their constipation-reducing efficacy.A constipation model was established with BALB/c male mice and loperamide hydrochloride.B.animalis subsp.lactis BB12 and phenolphthalein were used as positive controls.The indexes of constipation,including the mice health index,fecal water content,first black stool defecation time,the small intestinal propulsion rate,serum index,short-chain fatty acids(SCFAs)density in cecum contents and feces,colonic tissue structure and fecal microflora,were tested.It was determined that strain-specific effects were shown on fecal water content,first black stool defecation time,small intestinal propulsion rate and SCFAs in colon cecal contents.Compared with the control group,6 strains mainly increased the abundance levels of Bifidobacterium,Ruminococcus and Oscillospira in feces.Among the tested strains,B.longum subsp.longum CCFM760 significantly increased constipation mice's fecal water content,the propionic acid and total acid concentration of colonic content.And it also significantly shortened the first black stool defecation time about 38 minutes and showed a 24% raise in the intestinal transit.In general,B.longum subsp.longum CCFM760 could be used as a potential treatment for constipation.Finally,the safety of B.longum subsp.longum CCFM760 was evaluated.Real-time fluorescent quantitative PCR was used to determine the intestinal colonization ability of B.longum subsp.longum CCFM760.It was observed that the probiotic function of this strain could be maintained for one week.The safety of strains was assessed by antibiotic resistance tests.The results showed that the antibiotic minimum inhibitory concentrations of B.longum subsp.longum CCFM760 were less than the standard value.What's more,this strain's genome was sequenced and compared with B.animalis subsp.lactis BB12.The proportion of genes with function of adhesion and oligosaccharide utilization in B.longum subsp.longum CCFM760 was higher than that of B.animalis subsp.lactis BB12.In conclusion,by analyzing the physiological characteristics,animal experiments and gene sketch data of the strains,we found that B.longum subsp.longum CCFM760 contributed to relieving constipation and has great potential for practical application in the future.