Biochemistry, Genetics, and Applications of Exopolysaccharide Production in Streptococcus thermophilus: A Review

Abstract

Many strains of Streptococcus thermophilus synthesize extracellular polysaccharides. These molecules may be produced as capsules that are tightly associated with the cell, or they may be liberated into the medium as a loose slime (i.e., "ropy" polysaccharide). Although the presence of exopolysaccharide does not confer any obvious advantage to growth or survival of S. thermophilus in milk, in situ production by this species or other dairy lactic acid bacteria typically imparts a desirable "ropy" or viscous texture to fermented milk products. Recent work has also shown that exopolysaccharide-producing S. thermophilus can enhance the functional properties of Mozzarella cheese, but they are not phage-proof. As our understanding of the genetics, physiology, and functionality of bacterial exopolysaccharides continues to improve, novel applications for polysaccharides and polysaccharide-producing cultures are likely to emerge inside and outside the dairy industry. This article provides an overview of biochemistry, genetics, and applications of exopolysaccharide production in S. thermophilus.

Complete sequence and comparative genome analysis of the dairy bacterium Streptococcus thermophilus

“…In spite of the presence of homologs of the cps genes, which are involved in the synthesis of the capsule that is essential for virulence in pathogenic streptococci such as S. pneumoniae, the two S. thermophilus strains are not encapsulated. Their cps homologs, also known as eps, are involved in the synthesis of exopolysaccharides, important for the industrial use of S. thermophilus, as they confer the desired texture to yogurt 16 .…”

The interaction effect of mixing starter cultures on homemade natural yogurt’s pH and viscosity

“…S. thermophilus has the ability to breakdown lactose into glucose and galactose. S. thermophilus then proceeds to digest glucose monomers for growth (Broadbent et al, 2003;Drouault, Anba, & Corthier, 2002). Almost all formulations that contain S. thermophilus had high viscosity, especially when paired with L. acidophilus (formulation 8 and 10).…”

“…The key role of S. thermophilus is to breakdown lactose to lactic acid, and therefore reduce pH to preserve the product. S. thermophilus also produces secondary metabolites, such as exopolysaccharides and flavoured compounds (Broadbent, McMahon, Welker, Oberg, & Moineau, 2003). These probiotic starter cultures are now available for public use and sold in specialised shops for food ingredients.…”

Molecular characterization of an exopolysaccharide from a probiotic Lactobacillus plantarum MTCC 9510 and its efficacy to improve the texture of starchy food

“…EPS prevent syneresis and improve product stability firstly by increasing the viscosity and elasticity of the final product, and secondly by binding hydration water. Hydrocolloids are mainly used to improve mouth-feel, texture, visual and taste perception, storage stability, mechanical protection and prevention of syneresis in the final food products (Broadbent et al 2003;Hassan et al 2003;Sikora et al 2003). CMC or cellulose gum is presently used in food science as a viscosity modifier or thickener, and to stabilize emulsions in various products including ice-cream.…”