Selection Of Tolerance Stain Bifidobacterium Adolescentis And Microencapsulation

Bifidobacterium is a kind of probiotics in intestinal tracts of human, which has a lot of biological functions such as the functions of regulating human immunity, antitumour, anti-aging, improving the intestinal environment, keeping the intestinal balance, preventing and curing diseases. It is one of the evaluation indexes of human body health, so bifidobacterium are widely used in the field of food and drug. Bifidobacterium is a kind of strict anaerobic bacteria, the cultivation of Bifidobacterium is affected by oxygen, pH value and so on. Its development and application of bifidobacteria are limited.In order to gain tolerance to oxygen, acid and bile salt properties of strains, bifidobacterium adolescentis was selected as the original strain, and was mutanted by physical mutagenesis, chemical mutagenesis and domestication experiment. Through high density cultivation and microencapsulation, living bacterium agents were obtained by freeze drying technology. It was suitable for industrial production.In order to gain a strain with tolerance to oxygen, acid and bile salt properties, the original strain was mutated by UV irradiation, chemical mutagenesis, bifidobacterium adolescentis was selected as the original strain. The results showed that, effectness of UV irradiation was better than chemical mutagenesis. When UV irradiation time was70s, radiation distance was30cm from20w UV lamp, the ultimate pH of mutant strain was4.5, the ultimate consistency of bile salt was0.03%.Through the mutant strain was domesticated, the ultimate pH of mutant strain was3.0, the ultimate consistency of bile salt was0.2%.Based on the single factor experiment and the method of response surface, the optimized culture medium was:soya peptone30.52g/L, glucose36.33g/L,0.73mL/L corn syrup,Twain-801mL/L,L-cysteine0.5g/L, mixed salt solution10mL/L.Trough single factor experiment and orthogonal test. The optimized culture conditions were:pH7.8, noculation quantity was5%(v/v), temperature was42℃, The living bacteria number of Bifidobacterium adolescentisW70reached at2.41×108cfu/g.Cryoprotective agents were gained by single-factor test and orthogonal test. The result showed: trehalose concentration was80g/L, the concentration of glycerol was200mL/L, skim milk powder was lOOg/L and sucrose concentration was81.30g/L. Protective agent was added, the strain was microencapsulated by method of extrusion or method of emulsification. Living bacterium agents were obtained by freeze drying technology, and the living bacteria number of Bifidobacterium adolescentisW70reached at2.21×108cfu/g.Finally, the tolerance test of capsuled bacterial strain of resistant to gastric juice, cholate and intestinal juice was carried out. The results showed:the survival rate of microcapsuled Bifidobacterium adolescentisW70was46.37%after taking it into the simulated gastric juice for3h.The survival rate of microcapsuled Bifidobacterium adolescentisW70was26.74%after taking it into the bile salt solution (3.0g/L) for3h.Although enteric determination, microencapsulated bacteria could release in50min, there were still bfidobacterium adolescentisW70survive in intestinal juice.