Food colorant brilliant blue causes persistent functional and structural changes in an in vitro simplified microbiota model system

The human gut microbiota plays a vital role in maintaining host health by acting as a barrier against pathogens, supporting the immune system, and metabolizing complex carbon sources into beneficial compounds such as short-chain fatty acids. Brilliant blue E-133 (BB), is a common food dye that is not absorbed or metabolized by the body, leading to substantial exposure of the gut microbiota. Despite this, its effects on the microbiota are not well-documented. In this study, we cultivated the Simplified Human Microbiota Model (SIHUMIx) in a three-stage in vitro approach (stabilization, exposure, and recovery). Using metaproteomic and metabolomic approaches, we observed significant shifts in microbial composition, including an increase in the relative abundance of <i>Bacteroides thetaiotaomicron</i> and a decrease in beneficial species such as <i>Bifidobacterium longum</i> and <i>Clostridium butyricum</i>. We observed lower protein abundance in energy metabolism, metabolic end products, and particularly lactate and butyrate. Disturbance in key metabolic pathways related to energy production, stress response, and amino acid metabolism were also observed, with some pathways affected independently of bacterial abundance. These functional changes persisted during the recovery phase, indicating that the microbiota did not fully return to its pre-exposure state. Our findings suggest that BB has a lasting impact on gut microbiota structure and function, raising concerns about its widespread use in the food industry. This study underscores the need for further research into the long-term effects of food colorants on the gut microbiota and their potential health implications.