| The antibacterial characteristics of nineteen strains of Yeasts isolated from fifteen samples of koumiss collected from heardman,s house in Inner Mongolia were studied. The supernatants of five strains of Yeasts were shown to inhibit Escherichia coli growth.. Among them, there were also three strains could shown antibacterial property on Staphylococcus aureus, but as not strong as inhibiting property on Ecoli. Two strains of Brettanomyces, and one strain of Pachytichospora were identified from the five strains. One strain of Brettanomyces with higher inhibiting activity on bacteria was chosen for further study. The optimum antibacterial activity was obtained under the culture of glucose―yeast extract―peptone, culturing temperature of 27℃ and pH ranging 5.0~6.0. The antibacteria substance extracted by ethyl ether at pH value of 2 and 8 showed the greatest activity in the study. The antibiotic substance with a nature of neutral is not belongling to the Six Standard Antibiotics. The antibacteria substance composed with three kinds of proteins with molecule weight of 16300, 22100 , 25900 and one kind of small molecule substance. The small molecule substance showed stronger inhibiting activity on bacteria than the proteins. There were no significant differences of nature of antibacteria among the proteins. The results indicated that the antibacteria activity of antibacteria substance was affected significantly by temperature and pH value. As pH increasing, the higher temperature, the more the losses of antibacteria activity and the sunstance behaved insensitive to trypsin and pepsin.
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