Screening A Low PH Resistant Probiotic Saccharomyces Boulardii And Its Solid And Liquid Culture

Saccharomyces boulardii was first separated from lichi in Indonesia by a French scientist Henri Boulard in the early 1920s and named as Saccharomyces boulardii(S.boulardii).S.boulardii is a nonpathogenic yeast strains,and is the only yeast strains used for the treatment of gastrointestinal diseases as a probiotics drug in clinical.As a microecologics,it was regularly used in the treatment of diarrhea that caused by antibiotics and microbial infection,maintain the balance of the gastrointestinal tract microenvironment.Upon oral administration,a small quantity of living S.boulardii can reach the animals intestines,due to the poor tolerance of low pH.In order to improve S.boulardii tolerance to low pH,An ARTP mutagenesis approach and domestication was employed to generate low pH resistance S.boulardii mutants that showed a high rate of survival to wild type in low pH cultivation.In order to increasing the biomass of S.boulardii which was cultivated in 5L fermentor,we optimized the conditions of high density fermentation and the medium.Compared with liquid fermentation,solid-state fermentation has obvious advantages.It produces less waste,high product concentration.At the same time solid-state fermentation can use a variety of cheap agricultural residue as the substrate to produce high value-added products,and solid state fermentation is considered to be the best way to recycle renewable resources.So the production of S.boulardii by solid state fermentation also was preliminary studied.The results are as follows:(1)118 mutant strains were selected in the early screening,and 11 mutant strains were obtained after the secondary screening,Finally,we got 3 mutant strains that had a high tolerance at low pH.Acid resistance stability test indicated the survival rate of mutant strains YB-3 after cultivated 6h in pH2.0 was 50.83%.Compared with the control group(11%),the survival rate increased 462.09%.Also 3 strains were obtained through domestication and the survival rate of domesticated strains XH-3 was 34.01%,Increased 277.78%compared with the control group(9%).(2)Though the study,the cultivation conditions of high density fermentation S.boulardii by 5L fermentor:the inoculation was 10%,DO concentration was 30%,the glucose levels remained at around 0.5g/L in the fermentation process,the initial pH was 5.0,adjusted pH for 5.5 when reached the logarithmic phase,30? cultivated 36h.The final dry cell weight compared with the initial increased 55.52%and reached 58.79g/L,the cell yield was 0.4078g/g(DCW/glucose),compared with initial had an increase of 49%.(3)Though the study,determined the solid state fermentation cultivation conditions of S.boulardii:the inoculation was 15%,the content of urea was 7.5%of the bran,the content of K2HPO4 was 1.5%of the bran,30? cultivate 48h.At the same time,we compared the feasibility and economy of product by solid state fermentation S.boulardii with the substrate wheat straw,rice straw,malt spent and bran.Ultimately determined theeffect of bran as optimal,the number of living cells reached about 33×108CFU/g.