New Insights into Various Production Characteristics of Streptococcus thermophilus Strains

Abstract

Streptococcus thermophilus is one of the most valuable homo-fermentative lactic acid bacteria, which, for a long time, has been widely used as a starter for the production of fermented dairy products. The key production characteristics of S. thermophilus, for example the production of extracellular polysaccharide, proteolytic enzymes and flavor substances as well as acidifying capacity etc., have an important effect on the quality of dairy products. The acidification capacity of the strains determines the manufacturing time and quality of dairy products. It depends on the sugar utilization ability of strains. The production of extracellular polysaccharide is beneficial for improving the texture of dairy products. Flavor substances increase the acceptability of dairy products. The proteolytic activity of the strain influences not only the absorption of the nitrogen source, but also the formation of flavor substances. Different strains have obvious differences in production characteristics via long-time evolution and adaptation to environment. Gaining new strains with novel and desirable characteristics is an important long-term goal for researchers and the fermenting industry. The understanding of the potential molecular mechanisms behind important characteristics of different strains will promote the screening and breeding of excellent strains. In this paper, key technological and functional properties of different S. thermophilus strains are discussed, including sugar metabolism, proteolytic system and amino acid metabolism, and polysaccharide and flavor substance biosynthesis. At the same time, diversity of genomes and plasmids of S. thermophilus are presented. Advances in research on key production characteristics and molecular levels of S. thermophilus will increase understanding of molecular mechanisms of different strains with different important characteristics, and improve the industrialization control level for fermented foods.

Genome Analysis and Physiological Characterization of Four Streptococcus thermophilus Strains Isolated From Chinese Traditional Fermented Milk

“…Meanwhile, this bacterium could synthesize some beneficial molecules, such as exopolysaccharide (EPS), aromatic compounds, and formic and folic acids, which contribute to many desirable production characteristics of dairy products including viscosity, texture, flavor, and water holding capacity, etc. (Hols et al, 2005;Cui et al, 2016Cui et al, , 2017. Furthermore, it has been confirmed that S. thermophilus has various health benefits such as antiinflammatory activity, antimicrobial activity, antioxidant activity, as well as immunomodulation (Junjua et al, 2016;Cui et al, 2017;Uriot et al, 2017).…”

“…The carbohydrate utilization and sugar transport systems of CS5, CS9, CS18, and CS20 were analyzed (Figure 5). S. thermophilus takes up carbohydrates through a phosphoenolpyruvate (PEP)-phosphotransferase system (PTS) or a secondary transport system (Cui et al, 2016). The PEP-PTS consists of a PEP-dependent phosphotransferase (enzyme I, EI), a histidine-containing phosphocarrier protein (HPr, heat-stable protein), and a sugar-specific permease (transporter), which is a membrane-bound complex known as enzyme II (EII).…”

“…Streptococcus thermophilus is a necessary starter culture for yogurt manufacturing and widely used in yogurt and cheese production worldwide (Cui et al, 2016;Uriot et al, 2017). It has rapid acidifying capacity during milk fermentation and accelerates the coagulation of milk proteins.…”

Proteomic analysis reveals potential factors associated with enhanced EPS production in Streptococcus thermophilus ASCC 1275

“…Initial step in EPS biosynthesis is the transport of sugars from the external environment into the cytoplasm 16 . The general transport systems found in S. thermophilus 1275 are group translocation systems, primary transport systems and secondary transport systems 18 . Group translocation systems are dependent on phosphoenolpyruvate (sugar) phosphotransferase (PEP-PTS).…”

“…Phosphorylation of the sugars transported into the cytoplasm determines its fate. Nucleotide sugars that lead to EPS biosynthesis are formed from sugar-1-phosphates, while sugar-6-phosphates enters glycolytic pathway 18 . In S. thermophilus 1275, glucose and sucrose are transported into the cell using PEP-PTS transporters that lead to the formation of sugar-6-phosphates.…”