Preparation And Characterization Of β-(1-3)-D-Glucan From Waste Brewer’s Yeast

As one of the the best active immune polysaccharides, β-glucan accounts for30-60percent of total brewer’s yeast cell wall by dry weight. The yield of spent beer yeast is morethan60,000tons (dry weight) every year in China, the vast majority of spent beer yeast wasdirectly discarded or simply processed to normal forage and sold cheaply, but both of theprocessing methods has low added value. If we can extract β-glucan from spent beer yeast andbe used to all trades and professions, the way will bring enormous social influence. In thispaper, we adopt the method of autolysis-hot water extraction-ultrasonic disruption to extractβ-1,3-D-glucan from spent beer yeast, a series of key factors influencing of yeast autolysis,hot water extraction and ultrasound disruption are discussed, moreover, the purificationmethod and properties of β-1,3-D-glucan product was study deeply. The major findings ofthis paper are as follows:1. The optimum procession conditions of spent beer yeast autolysis were determined bysingle-factor experiments and orthogonal test through studying the key factors of influencingof spent beer yeast autolysis, the optimum conditions were as follows: the autolysistemperature and autolysis were50℃and5.0respectively, the NaCl addition and autolysistime were3%(w/w) and24h respectively.2. The optimum procession conditions of spent beer yeast hot water extraction weredetermined by single-factor experiments and U5(52) uniform design table test, tehe optimumconditions were as follows: the extraction temperature and extraction time were115℃and4h respectively.3. The procession of yeast ultrasonic disruption was optimized by single-factor test andBox-Behnken orthogonal factor analysis test, the main factor of influencing of spent beeryeast ultrasonic disruption was ultrasonic power X2,secondary factors were ultrasonic time X3and ultrasonic temperature X4respectively. The optimum conditions for the spent beer yeastultrasonic disruption were as follows: the yeast concentration and ultrasonic power were200g/L and800W respectively, the ultrasonic time and ultrasonic temperature were80min and50℃respectively,.4. In this paper, four kinds of methods including alkali method, acid-alkali method,enzymatic method and enzymatic-alkali method for removing protein from yeast glucanproduct were compared, all of these four methods, the content of protein is the lowest andproduct purity is the highest when adopting enzymatic-alkali method,the product purity is90.63%, the yield rate is10.31%, while the product purity is90.63%and the yield rate is 10.31%when Ma Sen adopting ultrasonic sound-enzymatic-alkali method, in a word, theproduct purity and the yield rate is further more in my experiment.5. The product obtained in our experiment being the high purity yeast β-1,3-D-glucanwas manifested by solubility analysis, color test, thin-layer chromatography and infraredspectroscopy test, besides, the product didn’t contain mannan.6. A reasonable technology for preparation of yeast β-1,3-D-glucan was obtained: wastebeer yeast was centrifugated and cleaned up to supernatant without beer flavor, the sedimentwas distilled into water for preparation of10%(w/w) suspension, then added3%NaCl intothe suspension, the yeast was autolysised for24h under the conditions of pH5.0andtemperature50℃, then the suspension was extracted for4h in the hot water under115℃,theprecipitation was collected after centrifuged, the sediment was made into concentration of200g/L yeast suspension, the cell wall was broken using ultrasound under the conditions ofultrasonic power800W, temperature of50℃maintaining80min, collected sediment aftercentrifugation, precipitation was distilled into water according to the ratio (w/w=1/3), thenadded papain (200u/g substrate), enzymatic hydrolysis for8h under pH6.0and60℃, theprecipitation was distilled into3%NaOH solution according to the ratio (w/w=1/5) plus,preparation for3h under75℃, then centrifugation and washing, using ethanol (w/w=1/2)washed the sediment and freezed-drying, at last, we gained the finished product.