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.

Subtilisin NAT, a subtilisin-like serine protease present in fermented soybean “natto” extract, inhibits <i>Streptococcus mutans</i> biofilm formation

“…This result was consistent with the inhibition of biofilm formation by commercially available subtilisin NAT: the presence of approximately 0.05 and 0.02 U/mL medium of commercially available subtilisin NAT reduced the safraninstained biofilm by about 80 % and 20 %, respectively (data not shown). These results strongly support our previous conclusion that subtilisin NAT is the biofilm inhibitor in natto extract (Iwamoto et al, 2018;Narisawa et al, 2014). Kitagawa et al (2017) showed that the natto peptide, which consists of 45 amino acid residues, has a bactericidal effect against Grampositive bacteria, such as S. pneumoniae and some Bacillus species; however, in our study, the natto extracts did not affect S. mutans growth in a liquid medium (Fig.…”

“…Natto, a fermented food product made from soybeans using Bacillus subtilis natto as a starter strain, is currently one of the most widely consumed fermented foods in Japan. In our previous study, a water-soluble fraction from a commercially available natto product interfered with the sucrose-dependent biofilm formation of S. mutans without reducing viable cell numbers (Iwamoto et al, 2018). Our results indicated that natto could be used as a safe functional food with anti-caries activity.…”

“…Our previous conclusion (Iwamoto et al, 2018;Narisawa et al, 2014) was also supported by the results of biofilm formation assay on HA discs: biofilm formation on the HA disc surfaces was also inhibited by the natto extracts made with the wild type strain (protease activity: 0.14 U/mL medium) and commercially available subtilisin NAT (0.10 U/mL medium), but not by the natto extracts made with the aprN − strain (protease activity: 0.02 U/mL medium) (Fig. 3).…”

“…The crude protease fraction obtained from commercially available natto inhibited water-insoluble glucan production (Iwamoto et al, 2018) (Liao et al, 2014), the genetics and physiology of the competence cascade through extracellular peptides (Li et al, 2002), and amyloid fibers on the cell surfaces (Besingi et al, 2017). Further studies are required to determine the target of subtilisin NAT for the inhibitory action.…”

The Effect of Probiotics Use on Salivary Cariogenic Bacteria in Orthodontic Patients with Various Caries Risk Status

“…Kolodkin-Gal et al found that Bacillus subtilis inhibited the formation of bacterial biofilms and triggered the scattering of mature biofilms by synthesizing D-tyrosine, D-leucine, D-methionine, and D-tryptophan [ 18 ]. The study by Iwamoto et al stated that natto made from soybeans cultured with Bacillus subtilis natto inhibits the formation of biofilm [ 19 ]. The study of Martin et al showed that Bacillus Natto was able to destroy the preformed biofilm [ 20 ], which might explain the mechanism by which the probiotics used in our study worked.…”