Exopolysaccharide production in milk by Lactobacillus delbrueckii ssp bulgaricus CNRZ 1187 and by two colonial variants

A ropy strain of Lactobacillus delbrueckii ssp, bulgaricus (CNRZ 1187) and two stable colonial variants produced different yields of neutral heteropolysaccharides when grown in milk. The variants were pink and white colonies, selected with ruthenium red from the parental strain. There were few differences among the strains in pH, lactic acid production, and lactose utilization over 24 h of fermentation. The relationship was fairly good between the exopolysaccharide yields and viscosities measured after 24 h of incubation. The pink colonies produced the highest amount (130 mg/L), the white colonies produced the lowest (70 mg/L) amount, and the parental strain produced an intermediate amount (110 mg/L) of exopolysaccharides. Approximately half of the polysaccharide was produced during the exponential growth phase. The polysaccharide contained mainly galactose and glucose with small amounts of mannose. In addition, arabinose was present in the polysaccharide from the pink and white colonies but not in that from the parental strain. The proportions of the monosaccharides in the polymers from the parental strain and the two colonial variants changed constantly during the fermentation cycle, but the variations were not the same for the three strains.