Preparation And Properties Of Bioactive Peptides And β-glucans From Yeast

Saccharomyces cerevisiae is a kind of single-cell micro-organisms with protein contenthigh up to50%.The yeast protein is a high quality protein which has a complete profile ofamino acid. It has been found that the yeast polysaccharide can enhance immune activity,antitumor activity, and promote the growth of intestinal bacteria breeding in order to improvethe intestinal environment and other physiological function. Preparation of bioactive peptidesand β-glucans from yeast can make full use of the yeast resource. It can not only reduceenvironmental pollution, but also by extending the yeast industry adds tremendous economicand social benefits. In this study, the peptides and β-glucans were prepared fromSaccharomyces cerevisiae by enzymatic hydrolysis and alkali-ultrasonic method. Then theydried by spray drying to get the products. The bioactivities of the peptides and β-glucans invitro were measured, and its chemical compositions and properties were also evaluated. Themain research results are as follows:1. The peptides were prepared from Saccharomyces cerevisiae using hydrolytic enzyme.The results of previous research had been used. The yeast peptide solution finally dried byspray drying with the inlet air temperature150℃to get the yeast peptide powder product.The chemical compositions and properties of the yeast peptide powder product has beendetermined. Basic compositions of the yeast peptide powder were determined and the maincomponent was peptides with content of53.12%±0.45%（w/w）. The solubility of the yeastpeptide powder is preferably at pH8, and it still have good solubility at high concentration. Inthe meantime，the yeast peptide powder has good water retention, water absorption and oilabsorption. Compared with the peptide solution， superoxide anion radical scavengingactivity, DPPH radical scavenging activity and α-glycosidase inhibitory activity of the yeastpeptide powder have a certain decline.2. The β-glucans were prepared from yeast cell wall by alkali-ultrasonic method. Theoptimum procession conditions for extraction yield were determined by the orthogonal testbased on the single-factor experiments. The results showed that the optimal conditions were:solid-liquid ratio1:35，NaOH concentration4.0%，time3.5h，temperature70℃，Ultrasonicpower250W and ultrasonic time80min. Under the optimum conditions，the extraction yieldis37.12%±1.04%（w/w）. The yeast water-soluble β-glucan solution was separated byultra-filtration which was concentrated. The content of water-soluble β-glucan was81.73%±0.21%（w/w）. 3. Physical and chemical properties of yeast water-soluble β-glucans were measured.Analysis of thin layer chromatography and IR, showed that the main monomer of the purifiedproduct is β-1,3-glucan. The Congo-red experiments prove that the β-1,3-glucan has triplehelix structure. The weight-average molecular weight of β-glucan was estimated to be40.8kDa which analyzed by GPC. The superoxide anion radical scavenging activity andDPPH radical scavenging activity of water-soluble β-glucan is weak.Prebiotic effect of yeastwater-soluble β-glucans was studied. The anti-digestibility of β-1,3-glucan were determinedby measuring their hydrolysis degrees. The maximal hydrolysis degrees of β-1,3-glucan inthe artificial human gastric juice were3.29%, and it was6.99%in the α-amylase. This provesthat the β-1,3-glucan has a good anti-digestible. The proliferative effect of water-solubleβ-glucan on probiotic has been studied. When water-soluble β-glucan was added to theBifidobacterium adolescentis basic culture medium as the amount of0.12%（w/V）, added tothe Lactobacillus bulgaricus basic culture medium as the amount of0.08%（w/V） the growth oftwo probiotics has brief lag phase and speeding up the growth rate. Therefore, water-solubleβ-glucan has potential to be exploited as a novel prebiotic.