Rheological properties of the mixture of Lentinan and saliva and its inhibitory effect on Streptococcus mutans

Lentinan (LNT) is extracted from the fruiting body of Lentinus edodes. Its active ingredient is & beta;-1,3-dextran and has many biological activities, but its rheological characteristics and antibacterial mechanism when mixed with saliva are rarely reported. In this study, the LNT and artificial saliva (AS) mixture was used to investigate the rheological analysis and antibacterial mechanism against Streptococcus mutans (S. mutans). The results showed that the apparent viscosity of the mixture was positively correlated with the concentration, showing a shear thinning behavior and a "non-Newtonian fluid" with a pseudoplastic behavior with the increase of shear rate. In dynamic rheology, the 8% and 6% mixtures became a gel trend and viscoelastic properties, showing elasticity of weak gel at low frequencies and liquid-like viscosity at high frequencies. Moreover, the compound could damage the structures of S. mutans and increased the leakage of intracellular macromolecules, electrical conductivity, and activities of alkaline phosphatase (AKP) and & beta;-galactoside but inhibited acid production, fluorescence intensity, and ATP synthesis by decreasing the levels of glucokinase (glk), acetate kinase (ackA), pyruvate kinase (pykf), phosphoglycerate kinase (pgk), 6-phosphofructokinase (pfk) in the glycolysis pathway. These results indicate that LNT plays a dominant role in the oral processing and antibacterial mechanism against S. mutans. It can provide an excellent theoretical basis for studying LNT as a functional food raw material.