Streptococcus thermophilus Strains: Properties and Microbial Consortia

Lactic acid strains require a comprehensive analysis prior to their use in new consortia with valuable production properties. Streptococcus thermophilus can be considered the second most important culture after Lactococcus lactis subsp. lactis. The natural intraspecific diversity of S. thermophilus makes it a promising consortium component for functional fermented products. This study investigated S. thermophilus strains (All-Russian Dairy Research Institute, Moscow, Russia) and their consortia using microbiological, biochemical, physicochemical, and proteomic methods. The S. thermophilus strains were tested for organic acids, vitamins, and enzymatic activity. The highest lactic acid content recorded was 6,643.5 mg/kg while the ability to synthesize vitamins B2 and B9 was straindependent. The cultures were rich in β-galactosidase. A proteomic analysis was performed to construct a matrix of functional protein distribution, revealing that several metabolic categories demonstrated pronounced strain specificity. To create microbial consortia with predictable properties, the strains were tested for biocompatibility with various probiotic cultures. The resulting data were used to design variants of microbial consortia, which were evaluated for sensory properties, fermentation activity, titratable and active acidity, and relative viscosity. The most promising S. thermophilus strains were incorporated into 18 multistrain consortia, nine of which demonstrated superior production-related characteristics.