Research On The Antioxidant And Antibacterial Activities Of Exopolysaccharides From Bifidobacterium Bifidum WBIN03and Its Benefical Effects On The Immunity And Inteatinal Microbiota In Mice

Exopolysaccharides (EPS), a long-chain polysaccharide produced by probioticsthat are secreted into the growth media during the metabolic process, have attractedmuch attention recently, mainly due to their potential health-promoting functions.EPS has been considered as a novel macromolecule that interacted with host receptorsand induced signalling pathways, resulting in probiotic effects. Therefore, it is aresearch hotspot for exploiting EPS from Bifidobacterium due to their specialbenefical functions.For screening the higher EPS yielding strain from nine bifidobacterium stored inour labolatory, the EPS yield and growth ability were measured. Bifidobacteriumbifidum WBIN03, which was able to adhere to the intestinal epithelial cells strongly,tolerate acid/bile salts/low temperature environment to a certain extent, and transferthe simulated gastrointestinal tract efficiently, could produce higer EPS (241.20±1.55mg/L) and grow rapidly (OD600=1.82±0.01) in the same conditions than thoseof other bididobacterium. Therefore, its EPS was isolated for further study.To investigate the antioxidant activities of exopolysaccharides from B. bifidumWBIN03, DPPH radical scavenging, hydroxyl radical scavenging, superoxide radicalscavenging abilities were measured as antioxidant activity. Reducing power,erythrocyte hemolysis inhibition and lipid peroxidation inhibition were also measured.Results showed that the scavenging ability against DPPH, hydroxyl and superoxideradicals of EPS at0.50mg/mL were78.16±0.30%,17.89±3.30%and33.34±2.40%, respectively, which were lower than that of ascorbic acid at the sameconcentration. The total reducing ability of EPS was significant higher than that ofascorbic acid at the concentration of0.50-2.00mg/mL (p<0.01). The anti-lipidperoxidation activities of1.50mg/mL B-EPS was33.68±1.63%, which was higherthan that of ascorbic acid at the concentration of0.50mg/mL (23.20±1.41%). Theinhibitory effects of EPS on erythrocyte hemolysis and inhibition rate were76.92±1.54%and61.43±6.03%at the concentration of1.00mg/mL, respectively, which were significant higher than that of0.50mg/mL ascorbic acid. Furthermore, all thoseabilities were enhanced with increasing concentration of EPS.Agar diffusion assay showed that EPS exhibited antibacterial activities againsttested pathogens i.e. Cronobacter sakazakii, Enterobacter coli, Listeriamonocytogenes, Staphyloccocus aureus, Bacillus cereus, Salmonella typhimurium andShigella sonnei at the concentration of300μg/mL, and the biggest inhibion zone was17.17±0.76mm on S. aureus, and subsequently15.83±0.76mm on C. sakazakii,13.67±1.53mm on E. coli. But none inhibition action was observed on Candidaalbicans.To study the effects of EPS from WBIN03on the immunity and hepatoneralfunction preliminarily, the body weight, immune organs indices, splenic lymphocyteproliferation, serum IgG and biochemistry were measured using BABL/c micefeeding EPS. Results showed that no significant influence was observed on theindices of body weight, organs index, surum IgG and biochemistry (p>0.05), but theproliferation of T/B lymophocytes was enhanced significantly (p<0.01) after oraladministration with higher concentration EPS in vivo.To investigate the effect of EPS from WBIN03on gut microbiota, thecombination of viable cell count, denaturing gradient gel electrophoresis (DGGE) and16S rRNA sequencing were used to assess the microbial diversity in mice intestine.The results indicated that the EPS significantly increased the growth of Lactobacilliand total anaerobic bacteria, and exerted their inhibition effect on growth ofEnterobacteria, Enterococci and Bacaeroides fragilis. The DGGE analysis indicatedthat the EPS significantly increased the diversity of total bacteria and Lactobacilluswhile significantly decreased the diversity of Eenterobacteria. When received a lowdose of EPS, Bacteroidales sp./Lactobacillus sp. occupied the dominant position,and L. johnsonii, L. animalis and L. reuteri were identified as the dominant strainswhen received the high concentration of EPS.In conclusion, EPS from WBIN03had antimicrobial, antioxidant activities andcould be potentially applied to food industry. Meanwhile, it had benefit effect onprobiotics and antagonistic effect against pathogens, and stimulated T/B lymphocyteproliferation in vivo, but non-adverse effect on hepatoneral functions. The whole study provides a model for exploitation or development of more functional EPS andfuther studies are needed to investigate its benificial function and mechenisms inmolecular level.