Studies On Domesticating Of Bifidobacterium Bifidum And Optimizing Its Growth Conditions

A strain of Bifidobacterium bifidum was domesticated with the traditional cultivation method.After the oxygen-,acid- and bile saltresistance domestication,the resistant abilities of this Bifidobacterium bifidum were enhanced.The domesticated strain could grow well both in the oxygen and anaerobic environment,the cell density and concentration of L-lactic acid were all higher than the original strain.Then this study mainly discussed the proliferation of Bifidobacterium bifidum by some growth-promoting factors:carrot juice,potato juice,tomato juice and the Fructose- oligosaccharides,Xylo-oligosaccharides,lactose and galactose.This research also studied the best additions of these growth-promoti-ng factors and the growth curves of Bifidobacterium bifidum in the best additions.The results showed that,the best additions of the carrot juice, potato juice and tomato juice were all 3%.The proliferation abilities from strong to small were:carrot juice＞potato juice＞tomato juice.In the function saccharides growth-promoting factors,Fructose- oligosaccharides and galactose almo-st hadn't show good proliferation to Bifidobacterium bifidum.But Xylo-oligosaccharides and lactose comparatively had some promoting functions,and the best additions of Xylo-oligosaccharides and lactose were 0.8%and 1.0%respectively.Furthermore,this study compared the growth curves in the best additions during these growth-pro-moting factors. The method of orthogonal test was used to optimize the culture medium components and culture conditions.The optimized medium components for Bifidobacterium bifidum were as follows:1.5%soya peptone,0.8% tryptone,0.8%casein peptone,0.5%yeast extract,0.5%beef extract,1% glucose,1%lactose,and inorganic-salt added with original proportion. The optimized culture conditions for Bifidobacterium bifidum were as follows:initial pH value at 8.0,inoculation was 5%,the best growing inoculum age was 24 and the best L-lactic acid producing age was 36h, temperature was 41℃.Bifidobacterium bifidum growed very well in the S-L fermentor.In the S-L fermentor,the number of Bifidobacterium bifidum in broth and the acids production were both higher than in the triangle-bottle culture,and the utilization rate of glucose also higher than the latter.In the S-L fermentor,the OD₆₀₀ of the broth could reach 1.670,the cell density of Bifidobacterium bifidum as higher as 6.3×10⁸per mL,and the production of lactic acid also reached to 620(mg/100mL) in the optimized medium.The production curve of exopolysaccharides(EPS) was determined as phenol-sulfuric acid method.To optimize EPS production,it was found the optimum conditions were as follows:initial pH value at 8.0,inoculation 5%,temperature 37℃,inoculum age 36h,and the production of EPS wasn't below 270.0mg/L.