Antiadhesive and antibiofilm potential of Bacillus clausii derived biosurfactant against Streptococcus mutans, Enterococcus faecalis, and Candida albicans biofilms.

BACKGROUND: Oral biofilms are principal drivers of oral and dental diseases such as caries, periodontal disease, endodontic infections, and candidiasis. Conventional biocides can reduce microbial load but may irritate tissues and disturb oral homeostasis, limiting prolonged use. Biosurfactants represent a sustainable alternative strategy by modulating adhesion and biofilm structure rather than relying solely on direct bactericidal activity. Lipopeptide biosurfactants are particularly attractive due to their amphiphilic structure, surface activity, and reported antibiofilm properties. F7 is a crude biosurfactant produced by Bacillus clausii isolated from a crude-oil reservoir in Sumatra, Indonesia. This study evaluated its physicochemical properties and antiadhesive/antibiofilm activity against three clinically relevant oral pathogens: Streptococcus mutans, Enterococcus faecalis, and Candida albicans, in both single- and mixed-species biofilm models.

RESULTS: Fourier transform infrared spectroscopy (FTIR) analysis revealed absorption bands consistent with a lipopeptide biosurfactant. F7 reduced surface tension to 22 mN/m (critical micelle concentration (CMC) 158 mg/L; emulsification index 63%), confirming strong surface activity. No planktonic minimum inhibitory concentration (MIC) or minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) was observed within 0.6-10 mg/mL. However, at 10 mg/mL, the minimum biofilm inhibitory concentration (MBIC) of F7 against single-species were 43.5% (S. mutans), 40.9% (E. faecalis), and 78.8% (C. albicans), and the minimum biofilm eradication concentration (MBEC) were 50.0%, 43.5%, and 34.8%, respectively. In mixed-species models at 10 mg/mL, MBIC was 23.4% (S. mutans-C. albicans), 44.7% (E. faecalis-C. albicans), and 27.6% (three-species), whereas MBEC was 74.0% (S. mutans-C. albicans), 42.8% (E. faecalis-C. albicans), and 42.5% (three-species). Resazurin assays demonstrated concordant metabolic suppression, and field emission scanning electron microscopy (FESEM) revealed membrane and matrix-associated structural alterations consistent with surface-active lipopeptide activity.

CONCLUSION: Under the conditions tested, F7 functioned as an antibiofilm agent rather than a classical planktonic biocide. Notably, strong biofilm inhibition was observed against C. albicans, and the greatest biofilm reduction occurred in the mixed S. mutans-C. albicans consortium, accompanied by suppression of metabolic viability. These findings support a biofilm-modulating mechanism and suggest the potential of B. clausii-derived biosurfactants as non-biocidal adjuncts in oral biofilm management.