Breeding Of Salt-tolerant Ester-producing Yeast And Primary Studies On Using It In Soy Sauce Fermentation

Soy sauce is an important condiment or seasoning sauce. Soy sauce fermentation involves the high-salt liquid fermentation and the low-salt solid fermentation. In the high-salt liquid fermentation soy sauce has a salty taste and distinct fragrance due to long fermentation time and high utilization rate of raw material. Therefore, soy sauce is becoming popular worldwide. During the high-salt liquid fermentation aroma compounds such as ethanols and esters are produced, which is important to the flavor of soy sauce.In this study, ester-producing yeast {Hansenula anomala IFF1274) was treated with UV and Ethyl methane sulfonate (EMS). The starting mutant population of genome shuffling was obtained after selecting by high salt plates. Ten mutant strains were instructed after three rounds of shuffling. The strain H3-8was then selected by liquid media with high content of salt. The salt tolerance of H3-8was increased from120%to20%.Cells of H3-8were larger than those of the initial strain under magnification of800. No difference of morphology and the content of DNA were found between H3-8and the initial strain. H3-8had good metabolic activity and produced high content of ethanol and ethyl acetate in the presence of high salt concentrations (above18%).In high-salt liquid soy-sauce mash, H3-8well grew and validly utilized sugar. The log-phase came on the fifth day. The pH of soy sauce was enhanced. Moreover, the results of gas chromatography showed that the content of ethanol, ethyl acetate and acetic acid was improved after adding H3-8.Different content of H3-8was added to the soy-sauce mash and gas chromatography was carried out after cultivation of15days. The kinds of aroma compounds (about89kinds) were most when the content of H3-8was106. There were228.94730g/100L ethanol and887.67007g/lOOL acetic acid in the soy-sauce.H3-8was cultivated with S yeast and T yeast, respectively. The growth of H3-8was promoted by T yeast. Moreover, the production of ethanol, isobutyl alcohol and acetic acid was improved compared with adding T yeast alone. On the other hand, the growth of H3-8was inhibited by S yeast, which was not good for the soy-sauce flavor formation.The of Hansenula anomala IFF1274was improved by genome shuffling. In high-salt liquid soy-sauce mash, H3-8grew and produced ethanol, ethyl acetate and acetic acid, and the physical and chemical characteristics of soy-sauce had not obvious changes...