Exopolysaccharide (EPS)-Producing Streptococcus thermophilus: Functional and Probiotic Potential

Area of Science:

• Microbiology
• Food Science
• Biochemistry

Background:

• Streptococcus thermophilus is a key starter culture in dairy fermentations.
• Exopolysaccharides (EPS) produced by S. thermophilus can impart beneficial functional properties to food products.
• Characterizing EPS-producing strains from diverse sources like goat milk is crucial for identifying novel functional ingredients.

Purpose of the Study:

• To characterize exopolysaccharide (EPS)-producing Streptococcus thermophilus strains isolated from goat milk.
• To evaluate the structural and functional properties of the produced EPS.
• To assess the technological and probiotic potential of the selected S. thermophilus strains.

Main Methods:

• Isolation and characterization of S. thermophilus strains from goat milk.
• Fermentation analysis, carbohydrate utilization profiling, and enzymatic activity assays (e.g., β-galactosidase, aminopeptidases, acid phosphatase).
• Probiotic potential assessment: antibiotic sensitivity, antioxidant capacity, cholesterol-lowering ability, auto-aggregation, and co-aggregation with pathogens.
• EPS purification, structural analysis (composition, glycosidic linkages), and functional assays (antioxidant activity).

Main Results:

• Four S. thermophilus strains were isolated, showing efficient lactose fermentation and desirable enzyme activities.
• Strain GM4 exhibited significant probiotic characteristics: high β-galactosidase activity, moderate antioxidant and cholesterol-lowering abilities, and strong aggregation properties.
• GM4 produced a dextranase-resistant EPS composed mainly of glucose and mannose, with notable antioxidant activity.
• The EPS structure included specific glycosidic linkages, contributing to its functional properties.

Conclusions:

• Streptococcus thermophilus strain GM4 is a promising candidate for probiotic and functional food applications.
• The EPS produced by strain GM4 possesses significant antioxidant properties, suitable for incorporation into functional foods.
• Characterization of EPS-producing S. thermophilus from goat milk yields strains with valuable technological and health-promoting attributes.