| Bifidobacterium is a kind of important inhabitant bacteria in intestinal tracts of human. It has a lot of biological function such as preventing and curing intestine infection, modulation of the immunoloqical response and antitumour. It has direct beneficial effects on intestinal health. Bifidobacterium is widely used on doods and microecological medicines. However, Bifidobacterium is a kind of strict anaerobic becteria and needs rigorous culture condition. It is hard to get high viable count during fermentation which restricts the exploiture and application ofBifidobacteria production.Made research on the oxygen-resistance, acid proof, bile salt endurance of Bifidobacterium long. At this research, high density cells was got via fed batch cultivation and the freeze-drying technologic condition was screened out. Catalase was cloned, and positive recombinants were analyzed by bioinfbrmatics analysis1. Mutagenize the bacterial strain with U.V and DES, the mutant strain Bi-L80. Improve its tolerance, Bifidobacterium long can stable growth in the facultative anaerobic environment, after repeated domestication, Bi-L80 has a obvious improvement of tolerance to acid and bile salt. Tolerance pH value of 2.5, resistance bile salt concentration was 0.300%.LBifidobacteria long was cultivated with high density through the analysis of single factor and response surface.Get the optimization ratio of medium:soy peptone 2.05%, yeast powder 1.03%, glucose 0.90%, stachyose 0.63%, twain-801.0 ml/L, L-cysteine 0.5 g/L,mixed salt solution 10.0 ml/L, the optimized medium was named G-TPY. The optimized G-TPY medium was used to add supplementary food culture, the optimal flow pattern:pH6.5, temperature 40?, the sugar concentration arrange in 8.0-10.0 g/L. Number of living bacterium reached (2.71 ± 0.05) ×1010cfu/mL.3. The best protective agent formula was obtained by single factor and orthogonal experiments:12.5% trehalose, dried skim milk 7.5%,y-PGA 0.75%, measured survival rate was 85.04%. It could promise the number of living bacterium which the probiotics achieves the health care function due to its toleration of acid, bile, intestinal juice, three kinds of microcapsuk was tested in the environment of artificial simulation hydrochloric acid in gastric juice, bile and artificial simulation intestinal juice there are a fot of number of living bacterium, the microcapsules obtained within 2 h in intestinal juice completely collapse, there are still a tot of bifidobacterium survive long after disintegrate a4. Through the CAT gene sequences primer design which has been published on the NCBI. CAT gene sequencing was amplification from bacillus subtilis BS115,and then positive recombinant was sequencing. After sequencing amplification of CAT gene,sequence analysis shows that the CAT gene contained 1446 nucleotides, GC content is 49.59%, encoding 482 amino acids, relative molecular weight is 60745, the CAT gene have a signal peptide. CAT protein secondary structure prediction was test ed by SOPM secondary structure prediction.Alpha helix accounted for 26.61%(128), the beta-fold of 21.62%(104), beta Angle is 11.02%(53), random curl is 40.75%(196).Adopted the Swiss Model 3 d structure prediction server, lsi8.1.A was selected as the template, tertiary structure of protein was forecasting with the sequence of amino acids which the CAT gene coding. |
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