Properties Evaluation Of Bifidobacterium Animalis Subsp. Lactis BZ11、BZ25 And Preparation Of Biostime

Although Bifidobacterium is GRAS,we stilled need to pay more attention to the safety of it,especially new probiotic strains that had no safe use history for a long time.Bifidobacterium was a kind of obligate anaerobe.Moreover,the majority of Bifidobacterium had a low survival rate in low acid of the stomach and high bile salts of intestinal.It resulted to limit the functionality.Thus,the functional and safe properties of Bifidobacterium animalis subsp.lactis BZ11 and BZ25 were evaluated in vitro in this study,and then biostime microcapsules were produced.Our aim was to detect functional and safe properties of strains,and improve the stability and tolerance of acid and bile salts.First,the safety of strains was evaluated in vitro,included the toxicity test,drug susceptibility,plasmid,amino acid decarboxylase activity and the hemolysis activity.As a result,there were no acute toxicity,plasmid,biogenic amines and hemolysis activity existing in Bifidobacterium animalis subsp.lactis BZ11 and BZ25.Antibiotics sensitivity showed that strains were sensitive to penicillin,cephalosporin,macrolide and tetracycline,while resistant to aminoglycosides except neomycin,which provides some academic bases and references for application in the production of probiotic.Subsequently,the functional properties of Bifidobacterium animalis subsp.lactis BZ11、BZ25 and BB12 were assessed in vitro,such as acid and bile salts resistant,assimilate cholesterol,nitrite reduction,antioxidant capacity and exopolysaccharides(Bifidobacterium animalis subsp.lactis BB12 as control).As a result,all strains had excellent ability on acid and bile salts resistant.There was no significant difference on survival rate between pH 2.0,3.0 for 2 h and 0.3%,0.5%(m/v)bile salts for 24 h,survival rate of strains exceeded 90% respectively(p>0.05).The strain BZ11 had the best ability(26.59%)on assimilate cholesterol compared with the BZ25 and BB12.After 48 h,all strains had good performance on nitrite reduction(more than 90%).Scavenging free radical in supernatant better than that incells and cell-free extract for all strains on hydroxyl radical and DPPH,which suggested that the main active material existed in supernatant to effect free radical.On the hydroxyl radical,BZ11 was more excellent than BZ25 and BB12.All strains had a good scavenging on DPPH.However,all strains were poor on super oxygen anion removal(<10%).For the reducing capacity,BZ11 was the best with OD700 3.083.Moreover,BZ11 had the best EPS(118.03 mg/L)on after 48 h than BZ25 and BB12.Finally,the BZ11 as a candidate of microcapsule based on the results of previous study.Fructo-oligose could promote the growth of Bifidobacteria better as prebiotics,and the viable count increased from 8.60 Log CFU/mL to 9.34 Log CFU/mL,which increased from 26.59% to 37.43% on assimilate cholesterol.Sodium alginate was as the embedding wall because it had the better biocompatibility for Bifidobacterium animalis subsp.lactis BZ11.Primary embedding condition for produce of biostime microcapsules by extruding is sodium alginate optimum concentration 3%.0.8%(m/v)fructo-oligose along with BZ11 culture.As a result,embedding rate was 90.87%.Sodium alginate was used for secondary embedding.There was a significant difference among sodium alginate,whey protein and chitosan on embedding rate.Sodium alginate was the best(65.52%).Ascorbic acid and tea polyphenols were added to the microcapsule as antioxidants to produce antioxidant microcapsules.We compared with the bacterial liquid,primary microcapsule,secondary microcapsules without antioxidant and antioxidant microcapsules on survival rate of BZ11 in simulated gastric fluid,release in simulated intestinal juice and storage stability at 4 ℃.As a result,from big to small order on survival rate in simulated gastric fluid was secondary microcapsules,primary microcapsules,bacterial liquid.The number of bacteria from all microcapsules released to 8.00 Log CFU/g in simulated intestinal juice for 1 h.For storage at 4 ℃ for 24 h,the viable count from antioxidant microcapsules exceeded 8.00 Log CFU/g,which had better survival than others.Moreover,the tea polyphenols microcapsules was the best.