Screening and Extracting Mycocin Secreted by Yeast Isolated from Koumiss and Their Antibacterial Effect

Abstract

Koumiss is a common fermented mare’s milk with beneficial therapeutic effects on cardiovascular disease, tuberculosis, and diarrhea. The mare’s milk is fermented by lactic acid bacteria and yeasts. Although information about LAB from Koumiss is comprehensive, there is limited knowledge about yeasts from Koumiss and their effects. The purpose of this study was to screen and extract mycocin secreted by yeast isolated from Koumiss and test their antibacterial effect against pathogenic <i>E</i><i>scherichia coli</i><i>,</i><i> </i>The yeasts from Koumiss were isolated and those producing mycocin were screened by the Oxford cup method. Crude extracts of mycocin were then extracted by ethyl acetate, and temperature stabilities of them were investigated. The crude extracts of mycocin were tested against pathogenic<i> E</i><i>.</i><i> coli</i> and compared both <i>in vivo</i> and <i>in vitro</i>. Three Saccharomyces cerevisiae<i>,</i> and two <i>Kluyveromyces </i><i>marxianus</i><i> </i>were isolated from Koumiss in Inner Mongolia. All these yeasts produced mycocin. The two crude extracts of mycocin secreted by <i>K</i><i>. marxianus</i> were active and stable at temperatures between 25°C and 45°C. They had better antibacterial effect <i>in vitro</i> and <i>in vivo</i> and were shown to be effective in preventing <i>E. coli</i> disease in mice. It may be possible to use crude extracts of mycocin secreted by yeast isolated from Koumiss to inhibit the growth of <i>E. coli.</i>