The Japanese fermented food natto inhibits sucrose-dependent biofilm formation by cariogenic streptococci

Abstract

Our previous study indicated that certain commercially available proteases inhibit biofilm formation by cariogenic streptococci. Natto made from soybeans cultured with Bacillus subtilis natto contains an abundance of proteolytic enzymes. In this study, we investigated the correlation between the protease activity of extracts from 36 commercially available natto products and the inhibition of biofilm formation. The biofilm inhibitory effect was found to correlate with the level of protease activity in the natto extracts, without reducing the viable cell numbers. The natto extract markedly inhibited the production of a water-insoluble glucan by Streptococcus mutans, which is the main agent involved in the formation of biofilm by cariogenic streptococci. The characteristics of the protease present in the extract were similar to those of nattokinase. Our results indicate that the protease activity exhibited by extracts of the Japanese fermented food natto reduces the risk of caries by inhibiting biofilm formation.