The Study On Separating And Immobilization For A Salt-tolerance Acid-producing Yeast From Soy Sauce Mash

Adding salt-tolerant flavor-enhancing yeast could increase the flavor and aroma of soy sauce during the after fermentation period. In this study, premium light soy sauce mash of 25 days after fermentation from Xiamen Taohua Datong Brewing Co. was used as raw material. Using selective medium MRS #, a salt-tolerant acid-producing microorganism was isolated through several times of screening and purification. By the observation of colony morphology and cell microscopic morphology and a range of physiological and biochemical studies, it was indicated that this salt-tolerant acid-producing microorganism belongs to saccharomyces which was named as salt-tolerant acid-producing yeast JM01.The yeast was still able to grow and produced acid in YPD liquid fermentation medium of 22% salinity. Paper chromatography and gas chromatography showed that that acid was lactic acid. When the salt concentration of medium was 16g/100mL (the salinity was the same as normal soy sauce), the volume fraction of lactic acid was 1.94% in fermentation broth after 8 days culturing. In addition, it could grow in the condition of 16% ethanol. After a treatment of 60℃for 10 minutes, the yeasts were almost inhibited or killed.It was found that using calcium alginate as immobilization carriers was better than the agar gel and gelatin gel when doing the immobilized study on JM01. We chose calcium alginate as immobilization carriers for a further study. By single factor test and orthogonal test, it indicated that calcium alginate could be used as immobilization carriers with using conditions of 1.4 mol / L calcium chloride, 4% (w / v) sodium alginate, fermentation temperature of 32℃.In descending order of real fermenting factors which affect immobilizing salt-tolerant yeasts was: the concentration of sodium alginate> calcium chloride concentration of> fermentation temperature. The fermentation rate of immobilized salt-tolerant yeast was faster than the free salt-tolerant yeast and the alcohol production efficiency of immobilized salt-tolerant was 0.5 percentage points higher than the free salt-tolerant yeast.In order to study the industry production value of immobilized salt-tolerant acid-producing yeast, premium light soy sauce mash which just begun to enter the stage of after fermentation was used as sample in this paper. Researching the three kinds of fermentation forms of open not add yeast fermentation, airtight not add yeast fermentation, airtight immobilized yeast fermentation added, we found that it could obviously increase the ethanol content in soy sauce when adding immobilized salt-tolerant acid-producing yeast in closed soy sauce fermentation process, but the content of total acid and ester was lower which couldn't further enhance the aroma and some other flavor of soy sauce. In the open-style sauce mash fermentation, the content of acid and ester was higher but the alcohol smell was less, some would take shape of mold floating membrane, which seriously affected the quality of soy sauce. Therefore, how to use the salt-tolerant acid-producing yeast JM01 and the studied immobilization technology combing with the production equipment and process of the manufacturers and considering with the local geography, weather, and humanistic factors to brew high-quality soy sauce is still a key point of future research.