Fermentation-Derived 6-Shogaol from Zingiber officinale Rhizome Extract Inhibits Periodontal Biofilm Formation via Modulation of Quorum Sensing-Related Gene Expression

Microbial fermentation of plant-derived materials is increasingly recognized as a strategy to enhance biological activity through phytochemical bioconversion. In this study, we investigated the antibiofilm effects of fermented Zingiber officinale rhizome extract against major periodontal pathogens and examined the underlying mechanisms. Ginger extract fermented with plant-derived lactic acid bacteria showed significantly greater inhibition of biofilm formation by Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans than non-fermented extract. The inhibitory activity increased with fermentation time, resulting in approximately 60–70% reduction in biofilm formation at higher concentrations. Chromatographic analysis revealed decreased 6-gingerol and increased 6-shogaol levels after fermentation, suggesting bioconversion of 6-gingerol to 6-shogaol. Direct treatment with 6-shogaol inhibited biofilm formation in a dose-dependent manner in all tested pathogens. Quantitative PCR analysis further showed that 6-shogaol significantly downregulated the quorum sensing-related gene luxS and multiple adhesion- and virulence-associated genes, including flp, fimA, mfa1, radD, fadA, ltxA, and rgpB. These findings indicate that lactic acid bacterial fermentation enhances the antibiofilm activity of ginger extract through increased 6-shogaol production, highlighting its potential as a natural anti-biofilm and anti-virulence agent for periodontal disease prevention and management.