Selective production of two prebiotic extracellular polysaccharides from an oral probiotic lactic acid bacterium, Streptococcus salivarius SY511

Streptococcus salivarius is a lactic acid bacterium and an oral probiotic species. Growth of S. salivarius in a sucrose medium can lead to the production of exopolysaccharides (EPSs) that are potential prebiotics. However, no studies have yet examined use of this species for the selective production of high concentrations of EPSs. In this study, we isolated S. salivarius SY511 from infant feces and grew it in a sucrose medium to produce high levels of water-insoluble and water-soluble EPSs. NMR and monosaccharide analysis demonstrated that water-insoluble glucan and water-soluble levan were the two main EPSs. Batch fermentation in MRS-sucrose medium led to the efficient production of these two EPSs, and Tween 80 was a key factor that affected their differential production. In the fed-batch fermentation, 22.7 g/L of water-insoluble glucan was produced in the MRS-sucrose medium, while 24.9 g/L of levan was produced in the MRS-sucrose medium without Tween 80. Compared to S. salivarius M18, S. salivarius SY511 had higher or similar antimicrobial activity against major oral pathogens. Furthermore, the water-insoluble glucan and levan from S. salivarius SY511 had excellent prebiotic, anti-inflammatory, and antioxidant effects. Our study of S. salivarius SY511 identified a method for the selective production of two EPSs.