Isolation And Identification Of Bifidobacteria In Human Faeces In Parts Of China And Screening Of The Strains With Potential Probiotic Properties

In this study,29strains of Bifidobacterium were isolated from feces of18healthy persons from Henan, Sichuan, Tibet, Yunnan, Inner Mongolia and Xinjiang province by selective media, and they were identified by16S rRNA gene sequence analysis. B.animalis subsp.lactis V9was used as a reference strain, and the tolerability of these strains involving acid, artificial digestive juices and oxgall bile salt were studied.4potential probiotic strains with desired tolerability characteristic were selected. And then the fermentation characteristics and storage characteristics of these strains in skim milk was researched.The results showed that nine of29strains of Bifidobacterium isolated from healthy human feces were identified as B. longum, including IMAUFB064、IMAUFB065and IMAUFB091(6strains from Henan,2strains from Sichuan and1strain from Xinjiang). Twenty strains were classified as B. pseudocatenulatum, including IMAUFB071IMAUFB073. IMAUFB084、IMAUFB090and MAUFB092(9strains from Sichuan,7strains from Tibet,3strains from Yunnan and1strain from Inner Mongolia). There were24strains Bifidobacterium were growing well in modified MRS medium with pH3.0,3.5and4.0. Then the tolerability of24strains was respectively studied in artificial gastric digestion with pH3.0,2.5,2.0for3h. Finally, the2strains of Bifidobacterium wih higher survival rate than V9(84.97%) was selected as peotential probiotics strains, which were named as follows:IMAUFB084(85.98%) and IMAUFB073(85.66%). The screening proportion of potential probiotics strains in the total strains of Bifidobacterium is6.90%. The tolerance of strains in artificial gastric juice in different pH values were significant difference in strains level (P<0.05).With the pH value decreasing, the tolerance of the tested strains in the simulation of artificial gastric juice were decreased.4strains of Bifidobacterium had good survival rate in artificial intestinal juice at pH8.0for8h. The survival rate of IMAUFB090was101.8%, which was higher than that of the V9(97.84%). However, the survival rate of IMAUFB073(97.19%), IMAUFB084(94.38%) and IMAUFB064(89.93%) were lower than that of the V9.The maximum concentration of bile salt tolerance of4strains of Bifidobacterium was close to2.0%, but the later time of them was significant difference (p<0.05) in strains level. The later time of IMAUFB064was0.59h, which showed well tolerance to bile salt. The later time of IMAUFB084, IMAUFB073and IMAUFB090incidated that they were slight tolerance to bile salts strains; the later time of V9was0.25h, which showed V9was sensitive to bile salts. Obviously, the bile salt tolerance of the4tested strains was lower than the V9.IMAUFB064, IMAUFB073, IMAUFB084, IMAUFB090and V9were tested as single starter culture for the fermentation of skim milk. The results showed that the number of viable count of IMAUFB073at the end of fermentation was6.02×108after fermented18h. Meanwhile, IMAUFB090, V9, IMAUFB084and IMAUFB064get the end of fermentation time need about21h. The number of viable count was respectively5.44×108,5.13×108,3.91x108,3.33×108durring storage after fermention process. The rate of decline of pH values of the4tested strains was significantly lower than V9after storing14d. The viable count of V9and IMAUFB084were increased by0.06and0.01units (logcfu/g) after21d stroage. The number of viable count of IMAUFB064didn’t significantly decearsed. These results indicated that V9、IMAUFB084and IMAUFB064has a better storage stability than IMAUFB073and IMAUFB090, and these strains can be used as the candidate strains for the development of the probiotics.