DISSOCIATION AND STABILITY OF LACTOCOCCUS-LACTIS SUBSP LACTIS-357 CULTURE, WITH RESPECT TO SUCROSE-FERMENTING ABILITY AND EXOPOLYSACCHARIDE PRODUCTION

Strain 347 was found to harbour two subpopulations differing in their ability to utilize and ferment sucrose and to produce an exopolysaccharide on sucrose-containing media. The Suc+Eps+ (ts) variant (designated 347-S) grows poorly in milk, is defective in lactose and casein utilization, and does not coagulate milk. In contrast, the STRAIN 347-L, a sucrose metabolism and polysaccharide-deficient variant, (Sud(d)Eps(d) variant 347-L) is an efficient lactic starter. Both variants segregate the opposite type (though at different frequencies), thus exhibiting a phase variation-like behavior. Mixtures of L- and S-strains develop the original stable symbiotic substrain mixture containing about 3-4% of the S-type. Over the course of 3 years propagation in milk, the subpopulation ratio in strain 347 did not change appreciably.