The Reasons Of The Early Death Of Kluyveromyces Thermotolerans In Mixed Fermentation And Its Impact On The Wine Flavor

In wine fermentation brewing there are two main ways. One is pure fermentation, usingsingle specie, and the other is called a mixed fermentation, using two or more species. Eachway for fermentation has its own advantages. The operation process is relatively simple andeasy to mechanic and automatic in pure fermentation, and the quality of the finished wine ismore stable, but the flavor is poor compared to mixed fermentation. In contrast, the mixedfermentation is done under different interactions among several microorganisms. It’s difficultto control the interactions in industrial production, but the product produced by differentmicroorganisms in different mixed fermentation period could meet the diverse needs of thewine flavor, which is why the wine with a regional flavor.Based on the advantages of the two forms of fermentation, we selected two commonbacteria on the surface of grape skin: yeast (Saccharomyces cerevisiae FCC2144) andKluyveromyces (Kluyveromyces thermotolerans FCC2116), and mainly focused on:(1) The growth of two strains Saccharomyces cerevisiae in mixed fermentation;(2) According to (1), study on the extracellular protein of Saccharomyces cerevisiae andcellular proteins of non-Saccharomyces cerevisiae using two-dimensional electrophoresis, inorder to find the internal and external reasons of the decline of yeast.(3) Study on the effect of growth of microorganism on the final flavor of the wine.The dialysis tube was used to study the growth of a single strain, and intracellularprotein of non-Saccharomyces cerevisiae were analyzed by MALDI-TOF/MS, the resultsshow; during mixed fermentation, growth of the non-Saccharomyces cerevisiae changed a lotcompared with pure fermentation. The non-Saccharomyces cerevisiae exists in the wholefermentation process pure culture, while its survival time is shortened in the completelymixed fermentation and different molecular weight of dialysis bag fermentation, which wasthe early death. The inhibitory effect between cells can be alleviated to some extent byblocking the exchange of substances.To find the reason of the early death of non-Saccharomyces cerevisiae in the mixedfermentation, the extracellular protein of Saccharomyces cerevisiae and cellular proteins ofnon-Saccharomyces cerevisiae were analyzed. The results showed that: in pure culture, proteins secreted by Saccharomyces cerevisiae could induce the decline of Kluyveromyces,and the presence of Kluyveromyces would induce Saccharomyces cerevisiae secreted specificproteins. Analysis of Kluyveromyces intracellular proteins under different fermentationconditions using MALDI-TOF/MS suggest that the secretion of metabolites ofSaccharomyces cerevisiae led to some non-Saccharomyces cerevisiae in vivo energymetabolism, replication and repair genetic material and some protection protein synthesis andtransport-related physical changes, which caused the early death.Mixed fermentation compared with the pure fermentation, volatile acid (0.22<0.46g/L),acetaldehyde (30.61<82.50mg/L) and acetoin (5.62<14.33mg/L) were reduced. During thefermentation, the wine titratable acidity was significantly increased, and alcohol volatileacidity were decreased.