Absence of inhibitory effects of two new glucanases on streptococcus mutans growth

Abstract

Glucanohydrolases have shown promise in degrading exopolysaccharides in cariogenic biofilms, making them a potential strategy for biofilm control without disrupting the oral microbiota. However, their direct antimicrobial effects remain unclear. Aim: To determine the antimicrobial activity on S. mutans of two newly discovered glucanases characterized by our group, PmGH87 (mutanase) from Prevotella melaninogenica and CoGH66 (dextranase) from Capnocytophaga ochracea, using a commercial dextranase from Penicillum sp. as a control. Methods: Their effects on growth were assessed using a luciferase reporter system coupled with the promoter of the ldh gene in Streptococcus mutans. Results: Quantification of optical density and luminescence over a 10-hour growth period revealed that the commercial dextranase exhibited inhibitory effects on S. mutans growth. However, these effects were neutralized by heat treatment, suggesting the presence of a heat-sensitive contaminant or an additional antimicrobial property associated with the commercial dextranase from Penicillum sp. On the other hand, the purified mutanase and dextranase enzymes had no inhibitory effect on S. mutans growth. Conclusion: In conclusion, the absence of inhibitory effects on S. mutans growth by the newly discovered enzymes emphasizes their potential for biofilm control while preserving the delicate balance of the oral microbiota and preventing the emergence of resistance.