Isolation And Screening Of High-yield Saccharomyces Cerevisiae And The Preparation Of Yeast Liquid Koji

In liquor brewing,Ester yeast involving in alcohol fermentation,through self metabolism to produce esterifying enzyme and play an important catalytic role in alcohol brewing,esterifying enzymes dehydrated combine acids and alcohols produced by other function bacteria to generate esters who farther lead to the increase in ester contents,which enhances liquor aroma and improves liquor flavor.The distiller’s yeast,cellar mud and distillers’ grains were sampled from Heilongjiang rich Laojiao Wine Co.Ltd.,in this study.By classic microbial isolation and purification method,the pure culture of microorganisms was obtained.Yeast strains with high yield of ester and esterification enzymes were screened out via primary screening on gas and smell production,followed by secondary screening on total ester yield by acid contents and ester levels in fermentation liquid were measured using gas chromatography for validation and on esterification enzyme activity by a-naphthyl acetate colorimetry.The screened strains were identified through morphological characteristics,physiological and biochemical features as well as molecular biology method.Afterwards,the functional strains were subjected to fermentation condition study and complex test,the primary liquid distiller’s yeast was prepared.The impact factors were optimized through response surface methodology,and the optimal parameters and liquid distiller’s yeast of good quality were obtained.Five high ester yield strains were isolated from distiller’s yeast,cellar mud and distillers’ grains,by identification,they were turn out to be Pichia kudriavzvii,Zygosaccharomyces bailii,Saccharomyces cerevisiae,Torulaspora spP.kudriavzvii,Z.bailii and:S.cerevisiae were selected as the experimental strains for studying the optimum fermentation conditions:initial sugar concentrationl2°Bx,pH value is 5,culture temperature was 28 ℃.The optimum inoculum dose was optimized to be 5%,5%and 5%respectively,and primary liquid distiller’s yeast was obtained.Response surface method to optimize the impect factors of liquid distiller’s yeast,three significant factors were assigned to be Ethanol、KH2PO4、Daqu powder,their optimum concentration were 3.72mL/100mL、1.03g/100mL、4.05g/100mL respectively,the quality of distiller’s yeast was the best with cell concentration of 5.01 X 108CFU/mL.The preliminary application of liquid distiller’s yeast in liquor brewing in laboratory,corn and sorghum flour as raw material,the distilled into 35%(v/v)liquor,the total ester content were 2.5324g/L and 2.4311 g/L respectively;ethyl acetate content were 0.7214g/L and 0.6977 g/L respectively,liquor flavor fragrance pure,mellow taste,reach the state of Fen-flavor liquor quality standards.