Mutanase of Paenibacillus humicus from Fermented Food Has a Potential for Hydrolysis of Biofilms Synthesized by Streptococcus mutans

Abstract

Mutanase is an α-1,3-glucanase that cleaves the α-1,3-glucosidic linkages of glucan polysaccharides termed mutan. There has been interest in mutanase as it has the potential to be considered in preventive medicine. Previously, we identified the mutanase of Paenibacillus humicus from fermented soybeans and observed that the enzyme hydrolyzed insoluble glucans and mutan in vitro. Here we focused on the ability of mutanase in preventing dental caries. We proposed that the enzyme participates in the degradation of insoluble glucan biofilms in microplates, which were used as a model of biofilms on tooth surface. In this study, we investigated the potential of mutanase to hydrolyze insoluble glucan biofilms synthesized by a typical cariogenic streptococcus, Streptococcus mutans 10449, in 96-well microplates. The mutanase specifically hydrolyzed insoluble glucan biofilms composed of insoluble glucans synthesized by S. mutans. The mutanase hydrolyzed approximately 60% of S. mutans glucan biofilms in the wells and liberated oligosaccharides from the glucan films. We observed that recombinant mutanase could hydrolyze mutan biofilms, and the enzyme was characterized as an endo-α-1,3-glucanase because its hydrolysis of mutan biofilms, resulted in the predominant liberation of α-1,3-glucan tetrasaccharides. The present study suggests that Paenibacillus mutanase from fermented soybeans has potential application in preventive medicine because of its ability to degrade oral insoluble glucan biofilms.