Isolation,Identification And Characterization Of ?-Glucosidase Producing Yeast

Grape berries contain a large number of non-volatile glycoside aromatic substances,which are the main source of aroma components in wine varieties,and their hydrolysates can provide precursors for the synthesis of fermented aroma.These glycosides mainly release active aroma components through the action of various glycoside hydrolases.Beta-glucosidase can hydrolyze the glycoside-bound aroma precursors in wine,release volatile glycoside ligands,and form rich wine aroma.In the process of wine brewing,yeast,as the dominant microorganism in alcohol fermentation,has an important impact on the sensory quality of wine,and is also one of the main sources of beta-glucosidase.Screening yeasts capable of producing beta-glucosidase and studying the enzymatic properties of the beta-glucosidase produced by yeasts are beneficial to improving the aroma quality of wine.The conclusions are as follows:(1)Ninety-two strains of yeast were screened by YEPD medium,16 strains of yeast were Naganishia,accounting for 17.4%;13 strains were Rhodotorula,accounting for 14.1%;4 strains were Papiliotrema,accounting for 4.3%;8 strains were Cryptococcus,accounting for 8.7%;4 strains were Vishniacozyma,accounting for 4.3%;9 strains were Rhodotorula.Hanseniaspora accounts for 9.8%;12 yeasts are Saccharomyces,accounting for 13%;7 yeasts are Pichia,accounting for 7.6%;9 yeasts are Lodderomyces,accounting for 9.8%;10 yeasts are Candida,accounting for 10.9%.(2)Five strains of yeast were screened from the grape epidermis collected from Turpan Basin(Turpan and Shanshan)for producing beta-glucosidase.Their strain numbers were LCC-3,LC-3,LS-18,RX-10 and RX-10.1.The enzymatic properties of beta-glucosidase produced by them were studied.The results are as follows: Selected 5 yeast strains have the ability to produce pectolytic enzymes,LCC-3,LC-3,LS-18,RX-10 and RX-10.1,the enzyme activity was 183.27±2.30 U/mL?231.32±2.89 U/mL?165.92±2.01 U/mL?263.84±3.40 U/mL?261.04±4.23 U/mL respectively.The optimum pH were: 5.0?5.0?5.0?5.0?5.0,and optimum temperature were: 50 ??40 ??60 ??50 ??50 ? respectively.(3)The strains LCC-3(Saccharomyces),LC-3(Rhodotorula),LS-18(Naganishia),RX-10(Candida)and RX-10.1(Candida)have the ability to produce beta-glucosidase.The wine fermentation experiments between these four yeasts and industrial Saccharomyces cerevisiae(Top15)were carried out.The results showed that the analysis of fermentation products and aroma during wine alcohol fermentation process showed that Saccharomyces cerevisiae Top15 could produce beta-glucosidase.Mixed fermentation with the strains at a ratio of 1:10(MS3 combination)and adding the strains 48 hours earlier,it was found that the content of fermentation products and main volatile components were more than that of other combinations,and the content of volatile components was also more than that of other combinations.