Screening Ester-producing Non-saccharomyces Yeast From Southern Sichuan Liquor Pits In China And Its Potential Analysis Of Wine Aroma Enhancement

Esters are important aroma compounds in wine and related to esterase activity.Esterase can convert organic acids and alcohols into esters by direct esterification.Chinese liquor pits have very rich ester-producing non-Saccharomyces yeasts.In this study,the wild non-Saccharomyces yeast with higher esterase activity was screened from Southern Sichuan liquor pits in China,and mixed fermentation with commercial Saccharomyces cerevisiae was applied in synthetic grape juice to improve wine aroma.The main results are as follows:1.The biodiversity of non-Saccharomyces yeasts in Southern Sichuan liquor pits of China.The morphological identification of yeasts on the WL solid medium found that 35 non-Saccharomyces yeasts were divided into 12 species,including Pichia kluyveri,Pichia fermentans,Lodderomyces elongisporus,Wickerhamomyces anomalus,Torulaspora delbrueckii,Pichia anomala,Debaryomyces hansenii,Hanseniaspora uvarum,Rhodutorula mucilaqinosa,Pichia membranefaciens,Candia catenulate,and Zygosaccharomyces bailii.The results showed that the yeasts isolated from Southern Sichuan liquor pits in China were biodiversity.2.The optimization of Pichia fermentans with higher esterase activity and the adaptability of esterase in wine making environment.The cellular location of esterase activity,which determined by p-NPB,found esterase of non-Saccharomyces yeasts mainly consisted in intracellular.The esterase activities of 35 strains of non-Saccharomyces yeasts were determined.One yeast with higher esterase activity was selected,and identified as P.fermentans.It was found that esterase activity reached the maximum 12.68 U/g at 40 oC,pH 5.0.Although the level of glucose,alcohol and SO2 inhibited esterase activity,but esterase had good adaptability in wine fermentation environment.3.Potential of wine aroma enhancement in mixed fermentation of P.fermentans and S.cerevisiae.During the treatments,the yeasts population in mixed fermentation were higher,especially the 96-h sequential inoculation.Substrate specificity of different carbon chain lengths(C2 ~ C8)on esterase found the total accumulated esterase activities of the simultaneous inoculation were the highest.C8 accumulated esterase activity was the highest,while C2 accumulated esterase activity was the lowest.The aroma analysis of different wine samples of mixed fermentation showed that there were 35 kinds of aroma compounds,the total content was 70~194 mg/L,and the eaters aroma was the highest at the 48-h sequential inoculation(S48).Compared with the pure fermentation of S.cerevisiae,mixed fermentation improved the content of isoamyl acetate,ethyl butyrate and butyric acid significantly.