Study On Optimum Extraction And Immunogical Activities Of Yeast Polysaccharide

Yeast is a kind of eukaryotic microorganism, and closely related to humanproduction and life. The yeast cell wall is100-400nm thick, and nearly75%of the dryweight yeast cell wall is polysaccharide. Yeast polysaccharide (YPS) is a kind ofpolysaccharides complex, and show a strong biological activity, such as potentinducers of cellular and humoral immunity. Besides, it could also combine with theextrinsic pathogen, balance the enterobacteria, acted as an anti-oxidant agent,anti-radiation, resist tumour.On the basis of single factor experiment, the method of response surfacemethodology (RSM) analysis on the extraction yield of polysaccharides was adoptedwith3factors including high pressure time, ultrasonic power and ultrasonic time, andthen the mathematical model was established by the Box-Behnken central compositeexperimental design, through response surface analysis.The optimum conditions obtained through RSM analysis as: high pressure timewas35min, ultrasonic power was510W, and ultrasonic time was26min. Thepredicted extraction yield of YPS was29.82%and the average actual extraction yieldof YPS was29.84%in these conditions.Monosaccharide compositions of YPS was analysed by thin layerchromatography (TLC), and the content of monosaccharide in YPS was tested byDual Wavelength TLC Scanning. The results indicate that the main component ofpolysaccharides was glucosan, and the content was29.69%.In order to evaluate the physiological functions and antagonistic effect of yeastpolysaccharide (YPS) on immunosuppression rats induced by cytoxan (CTX). A totalof80SD rats were randomly assigned equally into five groups: the control group, theCTX model group, the CTX-YPS（50mg/kg）group, the CTX-YPS（100mg/kg）group,and the CTX-YPS （200mg/kg） group. The rats in CTX-YPS groups wereintragastricaly administrated daily with YPS at the designed dose and weighed everyday; and the CTX model group and control group were intragastricaly administrateddaily with saline at the same time, once a day for7successive days. Except the control group, the rats in other groups were intraperitoneally injected with CTX (100mg/kg) on day5and6respectively. On day8, blood, immune organ and tissuesamples from in each group were collected. The growth performance, immune organsindex, the content of IgA, IgG, epidermal growth factor (EGF), alkaline phosphatase(AKP), lysozyme (LZM) in serum, SIgA in jejunum secretion and prostaglandin E2(PGE2) in colon were investigated. And the intestinal mucosa histologic changes wereobserved. Results indicated that the average daily gain (ADG) of YPS (100mg/kg)group increased significantly than control group (P <0.05), the Gain/Feed was alsosignificantly increased (P <0.05). The immune organs index of each group wassignificantly lower than control group after injected CTX (P <0.01), spleen index hadno significant difference between each group (P>0.05); the thymus index ofCTX-YPS (100mg/kg) group increased33.33%than CTX model group (P <0.05).The content of IgA, IgG, AKP in serum of CTX-YPS (100mg/kg) group weresignificantly or very significantly higher than CTX model group (P <0.05or P <0.01). And the content of LZM in CTX-YPS (100mg/kg) group had been improvedbut had no significant difference compared with CTX model group (P>0.05). Thelevel of SIgA and EGF in CTX-YPS (100mg/kg) group was improved verysignificantly (P <0.01) and significantly (P <0.05) compared with control grouprespectively. The content of PGE2in colon of CTX-YPS (100mg/kg) group wassignificantly reduced compared with CTX model group (P <0.05). Bowel mucosaepithelial of CTX model group was seriously damaged, the CTX-YPS (50mg/kg)group and CTX-YPS (200mg/kg) group also had varying degrees of injury, butCTX-YPS (100mg/kg) group were basically at normal state. YPS can improve thegrowth performance of rat; YPS has significantly protective effects andimmunomodulation against immune injury induced by CTX, and the most effectivedose is100mg/kg.