Study On Potential Symbiosis And Fermentation Characteristic Between Lactic Acid Bacteria And Yeasts Isolated From Koumiss

12 lactic acid bacteria (LAB) and 8 yeast strains, previously isolated from koumiss samples of Xilinguole region (in Inner Mongolia of China), were applied for potential symbiosis characteristic screening. Metabolites of LAB and yeasts were added into medium of each other as test groups, while control groups were added the same volume of saline. Their turbidity values and viable count were analysed when organisms got into stationary phase. Only yeast had positive interaction to LAB in one group and only LAB had positive interaction to yeast in three groups. Two pairs of LAB and yeast with positive interaction were screened out as follows: LC1 and YE3, YE4 and LC5. Among these positive interaction between LC5 and YE4 was highly significant (P<0.01).The fermentation characteristic of LC5 and YE4 co-cultured in skim milk medium and metabolites of LAB and yeasts were added into medium of each other showed that:â‘ The growth of LC5 during fermentation was advanced by the addition of YE4 metabolites, cause of YE4 metabolites retarded down the descent rate of pH value of fermentation broth, and titratable acidity was increased.â‘¡Likewise, the growth of YE4 was also advanced by LC5 metabolites with increased titratable acidity and decreased pH value, which approach the yeast optimum pH value.In the course of fermentation, the different content of FAN, organic acid, volatile flavor and vitamin in LC5 and YE4 co-cultured skim milk medium and pure culture showed that:â‘ The proteolysis ability of YE4 was better than LC5,and the proteolysis content of YE4 co-cultured metabolites was increased by LC5.â‘¡The lactic acid,propionic acid and isovaleric acid production of LC5 was increased by YE4, but no affect on ethanoic acid,butyric acid and pentanoate, the formic acid of LC5 was decreased by YE4. The content of malic acid,tartaric acid and citric acid in LC5 fermentation broth was increased by YE4.â‘¢The acetaldehyde production of LC5 was significantly increased by YE4 (P<0.05), but no affect on butanedione. The ethanol production of YE4 was decreased by LC5.â‘£In the course of fermentation, VA was produced by LC5 and YE4. VE was produced by LC5 and degraded by YE4. V_B1 and V_B2 was degraded by LC5 and YE4. The contention of V_A,V_E,V_B1 and V_B2 in mixed culture had no obvious changed compared with pure culture.