The Exploration In The Yeast Polysaccharide Extraction Method And Its Effects On In Vitro Fermentation Parameters

Extracellular polysaccharide production was taken as evaluation index in this test to screen out three strains of yeast from eight strains of yeast as bacterial source of the follow-up tests, in order to select a optimal extraction method of yeast polysaccharide compared the cell wall broken effects of different cell wall broken method after optimized the experimental conditions of ultrasonic broken, freezing and thawing, ultrasonic cleaning and protease treatment, the influence of adding yeast polysaccharide on sheep fermentation was explored at last by in vitro. Experimental results showed that the extracellular polysaccharide production of the eight strains of yeast was significantly different(P< 0.05),the extracellular polysaccharide production of Candida tropicalis I, Candida utilis and Saccharomyces cerevisiae II was significantly higher than other yeasts, taken them as the bacterial source of following test.After selected three strains of yeast, yeast polysaccharide extraction rate and cell wall broken rate were taken as evaluation index to explore the effect of the treatment time on the ultrasonic broken and the ultrasonic cleaning, and also the effect of moisture adding content-of bacterial sludge and the times of freezing and thawing on the repeated freezing and thawing were explored, at the same time the optimal conditions of protease treatment was determined by orthogonal test. From the research results we could know that when the ultrasonic time reaches for 40 minutes and 50 minutes respectively, the yeasts after treated by ultrasonic broken and ultrasonic cleaning reaches the maximum yeast cell wall polysaccharide extraction rate, and when the moisture adding content of the bacterial sludge and the times of freezing and thawing is 15% and 3 times respectively, the yeast cell wall polysaccharide extraction ra.te reaches maximum in the repeated freezing and thawing test, when the conditions of protease treatment were adding content of protease 300IU·g-1, enzymolysis time 15 hours, pH 5.0 and enzymolysis temperature 40℃, polysaccharide extraction rate achieved the highest value. And then the test focused the research on the wall-broken method of yeast for the purpose of selecting the optimal method of yeast polysaccharide extraction. After the process of ultrasonic broken, ultrasonic cleaning, repeated freezing and thawing and protease treatment, the corresponding yeast polysaccharide extraction yield were 0.29 mg·g-1,14.12 mg·g-1,3.70 mg·g-1 and 149.81 mg·g-1 respectively, the wall broken rate were 25.53%,98.96%,76.30% and 98.96%, then the test that combining the ultrasonic broken and protease treatment for purpose on exploring the influence of synergistic on cell wall broken result was did, the result of polysaccharide extraction rate and cell wall broken rate was 173.29 mg-g"1 and 99.47% respectively.The last-step test was did on the basis of above-mentioned research, the content of this part of the test is the effect of adding yeast polysaccharide under the different concentrate to forage ratio conditions on the fermentation parameters of sheep rumen. Results showed that different concentrate-roughage ratio had a significant influence (P<0.05) on the sheep rumen pH, gas production yield, dry matter degradation rate, microprotein, the concentration of NH3-N, molar ratio of acetic acid, propionic acid, butyric, acetic/propionic ratio. Influence of exogenous adding yeast polysaccharide on these nonspecific index of rumen were not significant (P> 0.05), but with the increasing of YPS (yeast polysaccharide) adding level, the pH tended to decrease.