Screening And Physiological Function Of Bifidobacteria

As an important part of human and animal intestinal flora, bifidobacterium hasmany physiological functions, including promoting digestion and absorption ofnutrients, inhibitting the growth of pathogenic bacteria, enhancing immunity and soon. In this study, bifidobacteria with acquired resistance to bile and low pH, wereisolated from the feces of healthy infant and adult. The results of our work are asfollows:(1) Totally75suspected bifidobacterium were isolated with MRSC added X-Galas selective medium. NCU712was in line with the characteristics of bifidobacteriumlongum and then identified as B. longum via physiological and biochemical tests and16s rDNA.(2) NCU712ferments glucose and produce organic acids, such as lactic acid andacetic acid.0-4h was lag phase of the bacterial growth,4-16h belongs to logarithmicphase, while16-24h was stationary phase and after24h, the bacteria entered thedecline phase.(3) The D value of NCU712were92.97min and30.42min in artificial gastricfluid with pH2.5and pH3.0. The number of living bacterium rose slightly in pH3.5and pH4.0, while stayed above108CFU/mL after4.0h in artificial intestinal fluid.The viable NCU712cells reduced an order of magnitude after incubating20h inMRSC with0.30%bile salt. In summary, NCU712has excellent tolerance to hunmangastrointestinal tract.(4) The adhesion of the bacteria in stationary phase was the best. The adhesionof NCU116was better with its concentration increase, but the growth tended tosaturation when the concentrtation was up to1.0×108CFU/mL. The growth leveledoff when the incubating time was up to2.0h. And furthermore, NCU712had a betteradherence in neutral environment.(5) The antioxidant effects of NCU712, including the capacity of DPPH radicalscavenging, hydroxyl scavenging, reducing power and inhibiting linoleic acidperoxidation enhanced with increasing the amount of samples. According to research,the antioxidant capacity of culture filtrate solution (CFS) were better than bateria onlyor its broken ecept hydroxyl scavenging ability, which bateria were the best. Most importantly, B. longum CFS displayed much stronger activity of DPPH radicalscavenging than that of vitamin C.(6) NCU712inhitbited the growth of seven common pathogenic bacteria, andfurthermore the inhibition of the fermented liquid was generally better than that ofCFS. The diameter of inhibition zone increased with the extension of fermentationtime until28h. NCU712metabolites can prolong the demurrage of salmonella andshorten the logarithmic phase. What’s more, the growth of salmonella is completelysuppressed when the concentration of NCU712CFS is more than12%.