Isolation Of Antibacterial Substances In The Koumiss And A Research On Their Antibacterial Properties

koumiss, a traditional and national dairy product in the Inner Mongolia, was researched.The antibiotic factors were preliminarily isolated from koumiss. Its antibiotic activity was detected by cylinder-plate method,which is similar to the determination of antibiotic liter. In order to get the best inhibitory effect on bacteria, Some factors that affected determination were analyzed. Many factors including density of the target strains, concentration of agar, culture time, thickness of the medium have effect to computation.The sensitivity and accuracy of the inhibitory test were improved. This study have also evaluated the inhibitory power of koumiss and analyzed the role of organic acids in bacterial inhibition. The results showed that organic acids in koumiss had apparent inhibitory effect to bacillus subtilis.Lactic acid was important for inhibition, the presence of acetic acid and alcohol improved the inhibitory effect. This inhibitory effect could be assigned to the undissociated form of organic acids. Lactic acid and acetic acid showed an inhibitory effect toward bacillus subtilis if the undissociated form was more than 0.683% and 0.256%, respectively. There are more than one antibacterial substances in the koumiss. If the fat of koumiss was separated into the neutral fat and the polary, we found that the neutral fat had a very effective inhibition to tubercle bacillus. By chromatography analyzing, there was no significant difference in fatty acid composition between the neutral fat and the polary. After ultra-filtrated, some substances in the whey of koumiss, which molecular weight was more than 10KD, had a powerful inhibitory effect to bacillus subtilis. By chromatography, an antibacterial substance was obtained, which molecular weight was about 15,400 . A further research were still needed.