Abstract: A total of 8 lactic acid bacteria (LAB) and 7 yeast strains that had previously been isolated from koumiss from Xilinguole region in Inner Mongolia of China were applied for potential symbiotic characteristic screening. Metabolites of LAB and yeasts were added interactively into their respective media in the treatment groups, while in the control groups the same volume of normal saline was used. The turbidity was monitored during the stationary phase. Three pairs of LAB (LC) and yeast (YE) with positive interaction were disclosed as follows: LC1 and YE3, LC4 and YE3, LC5 and YE4 , among which the positive interaction between LC5 and YE4 was highest (P <0.01). LC5 and YE4 co-cultured in skim milk medium showed an increased cell density compared to those obtained in separate culture. The further research showed that the growth of LC5 during fermentation was advanced by the addition of YE4 metabolites with increased titratable acidity and stable pH value. Likewise, the growth of YE4 was also enhanced by LC5 metabolites and the pH value was increased and almost reached the optimum value for yeasts.

Key words: koumiss, symbiosis characteristic, lactic acid bacterium, yeast, interaction, screening