Lactic Acid Bacteria (LAB), an important group of organisms in modern food production, are known to secrete a unique compound called exopolysaccharide (EPS). EPS is economically important because it enhances functional properties in food and may confer beneficial health effects to consumers. Novel strains of Lactococcus lactis, Streptococcus thermophilus, and species of Leuconostoc were screened for production of unique thickening EPS in 1% fat milk and lactose free milk. Other important characteristics were investigated, such as pH tolerance and inhibitory compound biosynthesis.
A natural isolate, L. lactis subsp. cremoris Ropy 352 that produces a distinct ropy EPS was previously analyzed and two unique genes, epsM and epsN, vital for the expression of the ropy phenotype were discovered. In this study, sequence analysis of two novel LAB, S.thermophilus R-39 and L. lactis subsp. cremoris 18-1, were shown to harbor genes similar but not identical to epsM and/or epsN. Interestingly, said LAB strains do not exhibit the ropy phenotype, which suggests the substituted amino acids may alter the function of the epsM and epsN proteins.