Bridging the gap of gut microbiome effects of new food additives in food risk assessment: MICODE gut model to test new chitosan from seafood waste

EFSA and FAO outlined guidelines to address data and methodological gaps in assessing the impact of food compounds on gut microbiota (GM) and human health, emphasizing the need for in vitro GM models and standardized biomarkers to integrate GM data into food safety risk assessments. Food texturizers are widespread in processed foods enhancing texture and stability, yet their effects on GM remain unclear. This study investigates three additives: a chitosan from seafood waste (CHIW), a chitosan standard (CHIC), and hydroxypropyl methylcellulose (HPMC), using fructo-oligosaccharides (FOS) as a prebiotic control. A standardized in vitro gastrointestinal model simulating digestion and colonic fermentation, combined with qPCR and GC–MS, assessed their influence on microbial composition and metabolic output, under the hypothesis that distinct carbohydrate polymers differently affect GM. CHIC and CHIW, derived from crustacean waste, promoted beneficial bacteria ( Clostridium group IV, Bifidobacteriaceae ) and boosted SCFAs production, including butyrate and propionate, with CHIW showing stronger prebiotic effects. HPMC was associated with reduced abundance of Lactobacillaceae and harmful metabolites. These findings support our hypothesis, demonstrate the responsiveness of in vitro GM models to dietary polymers, and reinforce the potential of GM-based screening in food safety assessment, suggesting native chitosan as a promising alternative to synthetic additives.