Screening on the symbiotic lactic acid bacteria and yeasts

Nine strains of lactic acid bacteria and eight strains of the yeasts isolated from koumiss had been screened to select the symbiotic strains. Metabolites were added to the culture mediums with the addition of the same amount of saline as control groups. Turbidity values and dry weight values were measured in the stationary phase. There were twelve combinations that the metabolites of lactic acid bacteria promoted the yeasts growth. Nearly half of the yeasts metabolites promoted the growth of lactic acid bacteria. Seven combinations showed there were a symbiotic relationship between the yeasts and lactic acid bacteria. In a conclusion, the symbiotic combinations were LAB2YST4, LAB4YST2, LAB5YST2, LAB7YST2, LAB7YST4, LAB8YST2, LAB9YST2 respectively. Among them, YST2 and other lactic acid bacteria had showed different levels of the symbiotic relationship between each other except LAB2. The symbiotic reasons needed further study.