Breeding Of High Salt-tolerance Yeast And Their Application In Soy Sauce Brewing

Soy sauce is a traditional Chinese fermented condiment, it has an unique color, aroma,taste and is deeply loved by the masses of people. The aroma composition of soy sauceis mainly produced during the combination of brewing microorganisms such as themold, yeast and lactic acid bacteria. The performance of the yeast directly affected thequality of soy sauce and flavor. The brewing of soy sauce is contained in the high saltenvironment, in order to get high quality of soy sauce, to obtain a yeast with a higherresistance to salt is very important for us.This article mainly has carried on the following several aspects work:1. A yeast survived in24%NaCl was selected from the chili sauce and would beapplied in the brewing of soy sauce. Through the strain morphologic identification, thesequence analysis of26S rRNA-ITS and phylogenetic analysis, the yeast has beenidentified as Zygosaccharomyces rouxii. It can be growth with60%glucose; growthtemperature range was from6℃to34℃; growth pH from4to7. The main compositionof fatty acid in the cell was C18. By the analysis of the aroma composition, the mainaroma produced by this strain was phenylethyl alcohol with a unique rose fragrance.Salt has little effect on the production of aroma components.2. With Torulopsis mogii as the research object, the mechanism of salt tolerancecaused by growth factor was studied. Firstly, the impact of growth factors on yeastgrowth showed that in the high salt environment, the added of biotin can obviouslypromoted the growth of Torulopsis mogii. With0.01g/L biotin supplementation, the cellgrew quickly thereafter, and achieved an apparent growth (OD600) improvement by50-100%and cell dry weight by18.5%, compared to that of the control. Further studyfound that intracellular trehalose content and the plasma membrane ATPase activity wasincreased by64%and48.8%. The ratio of K+/Na+in cell was improved by38.5%, theconcentration of Na+in cell reduced38.5%. Also the saturated fatty acids (SFA), theratio of SFA/USFA and C18/C16was enhanced by8.5%,14.3%and32.5%, relative tothe control, respectively. Combination of these results made Torulopsis mogii growbetter in the high salt tolerance. During the fermentation process, the main aromacomposition produced by Torulopsis mogii was ethyl acetate. The growth with biotin made the increase generation of alcohols, such as ethanol, n-butyl alcohol, phenylethylalcohol, silane double alcohol and so on.3. To apply the Zygosaccharomyces rouxii and Torulopsis mogii in the brewing of soysauce, the influence of some nutrients on the soy sauce flavor were also studied. Theeffect on the growth of yeast was inorganic nitrogen more obvisely than organicnitrogen than amino acid. Adding nitrogen source in the simulation of the soy saucefermentation medium for Zygosaccharomyces rouxii has a little influence on theproduction of aroma, the addition of inorganic nitrogen had a greater influence onTorulopsis mogii to produce aroma. These aroma included heptanol, heptanoic acid,octanoic acid ethyl ester, ethyl lactate, ethyl benzoin and furfural, etc.