Unveiling the impact of allulose on oral microbiota and biofilm formation via a cariogenic potential assessment platform

Introduction: The increased consumption of refined carbohydrates, particularly sucrose, has contributed to metabolic disorders and oral diseases such as dental caries by promoting dysbiotic biofilm formation and reducing microbial diversity. Allulose, a rare sugar with physicochemical properties similar to sucrose, has been suggested to offer metabolic health benefits; however, its impact on oral biofilm ecology remains unclear. Methods: We evaluated the cariogenic potential of allulose using a multi-tiered in vitro platform consisting of single-species planktonic and biofilm models, a dual-species biofilm model involving Streptococcus mutans (pathogen) and Streptococcus oralis (commensal), and a saliva-derived microcosm biofilm model. Key virulence indicators, including bacterial growth, acid production, biofilm biomass, exopolysaccharide (EPS) synthesis, and microbial community composition, were quantitatively assessed. Results: Compared to sucrose, glucose, and fructose, allulose supported reduced bacterial growth and acid production, showing a profile similar to non-fermentable sugar alcohols such as xylitol and erythritol. Biofilms developed under allulose conditions lacked the dense EPS-enmeshed microcolonies and dome-shaped architecture characteristic of sucrose-induced S. mutans-dominant biofilms. In the saliva-derived microcosm model, allulose-treated biofilms maintained higher microbial diversity and preserved health-compatible genera such as Neisseria, Haemophilus, Veillonella, and Granulicatella. Discussion: These findings demonstrate that allulose supports lower bacterial virulence activity and minimal biofilm formation compared to common dietary sugars while preserving microbial diversity. This highlights its potential as a non-cariogenic sugar alternative with microbiome-conscious benefits and provides ecological insight into how allulose may modulate oral biofilm structure and function.