DEVELOPMENT OF THE BIOTECHNOLOGY OF STREPTOCOCCUS THERMOPHILUS BACTERIA AS PRODUCERS OF EXOPOLYSACCHARIDESDEVELOPMENT OF THE BIOTECHNOLOGY OF STREPTOCOCCUS THERMOPHILUS BACTERIA AS PRODUCERS OF EXOPOLYSACCHARIDES

Abstract

On carrying out a screening, phage-resistant strains of Streptococcus thermophilus have been selected. As producers of exopolysaccharides, they can be used to form the texture of fermented milk and improve the rheological properties of fermented milk products in a natural, effective, and safe way. It has been suggested to use analysis of the capsule-formation of strains as an express method to evaluate the rheological properties. The technology of the bacterial concentrate Iprovit – Streptococcus thermophilus with phage-resistant producers of exopolysaccharides has been developed. The following technological modes were used: growing in a growth medium with the ratio of carbohydrates to soluble nitrogen C:N=3.5; biomass stabilisation (10% inulin protective medium, freezing at minus 60±1°C for 16±2 h, drying for 24±2 h to 32±1°C, moisture content in the preparation not more than 5%). These modes allowed obtaining 7.83±0.02 g of bacterial concentrate from 1 dm3 of the growth medium. Depending on the strain of Streptococcus thermophilus, the dry bacterial concentrate contained 4.4×1011–1.1×1011 CFU/g of active microbiota. A technique has been developed that allows improving the rheological properties of fermented milk products by blending bacterial preparations to produce various products with concentrate of the Streptococcus thermophilus strain. The optimal formulations of the mixtures have been selected. This has made it possible to modify the rheological characteristics of fermented products without using other thickeners. The effective viscosity of the products obtained has been increased by 13.3–54.3%, depending on the formulation of the mixture. The biotechnology of the bacterial concentrate Iprovit – Streptococcus thermophilus was implemented at the State Research Enterprise of the Institute of Food Resources, National Academy of Agricultural Sciences of Ukraine. Manufacture of the concentrate is regulated by the regulatory documents developed and approved: TU 15.5-00419880-100:2010 “Dry and liquid fermenting cultures. Specifications,” Technological Instructions for production of the fermented cultures IPROVIT for TU 15.5-00419880-100:2010 “Dry and liquid fermenting cultures. Specifications.” The novelty of the technological solutions was confirmed by Copyright Registration Certificate No. 51033.