We all know that dairy products are results of joint efforts of cows, which give milk, and bacteria, which make this milk sour via fermentation. Thus, we shouldn’t be surprised, when we find out that selectionists work not only with cows, but also with bacteria. Mentioned work is funded by the Russian foundation for Basic Research, and results of the investigation are published in the Biotechnology magazine.

Research fellows from State Science and Research Institute of Genetics and Selection of Industrial Microorganisms (SSRIGSIM) have discovered new strains of thermophilic Streptococcus, which can be used as starters in dairy food production. New strains show many valuable properties, such as splitting galactose, which is an unwanted compound in dairy products.

Thermophilic Streptococci are the only thermophilic dairy cocci, which Russian State Standards recommend for production of yoghurt, sour cream, ryazhenka (fermented baked milk, one of Russia’s favourites) and some sorts of cheese. Researchers from SSRIGSIM have studied 61 strain of thermophilic Streptococcus from lactobacteria, collected at the institute. Said lactobacteria were isolated from home-made dairy products from various Russian regions, as well as Ukraine, Italy, Croatia, Slovenia and France. After thorough tests scientists have selected several valuable bacterial strains for further studies and applications.

Said strains are valuable for several reasons. First, they are able to acidify growing substrate quite fast, thus making it suitable for production of dairy foods. Second, these microorganisms can synthesize polysaccharides and excrete them into environment. Polysaccharides make dairy products denser and slow down aliquation, which is important for production of cheeses, yoghurts and low-fat milky desserts. Ideal strain of thermophilic Streptococcus allows avoiding stabilizers and thickening agents – less chemistry, more health.

The most valuable property discovered in some Streptococcus strains is the ability to ferment galactose, which is not common for these microorganisms. It is lactose (milk sugar), which thermophilic Streptococcus strains usually consume and process very fast. Lactose is a disaccharide consisting of two monosaccharides – glucose and galactose. Streptococci pick glucose, as a most convenient energy source, leaving galactose unconsumed. There are several reasons galactose is an unwanted guest in foods. Human organism is not suitable for assimilating galactose, thus its excess may do harm. Galactose is the reason why mozzarella cheeses get dark with time and why putrefactive and pathogenic bacteria appear in dairy products. That is why Moscow scientists have chosen five thermophilic Streptococcus strains, able to assimilate galactose. Abovementioned strains can be very helpful as starters in production of dairy products for people, who are unable to assimilate galactose.

Source:
    Russian Science News

Kizilova Anna