D3.401 - A mechanism for loss of biodiversity in the gut: Toxic effects and metabolic alterations of food additives on human fecal microbiome

The gut microbiome is a complex microbial ecosystem essential for intestinal barrier integrity and immune homeostasis. While food additives are widely used in modern diets, their direct effects on gut microbial growth dynamics and functional responses remain poorly characterized. Here, we systematically examined the impact of commonly used food additives on human fecal microbiome growth under anaerobic conditions.

Fecal samples from healthy donors were transferred to an anaerobic chamber within two hours of collection, diluted to a 10⁻² slurry in sterile PBS, and inoculated into culture media containing graded concentrations of food additives, including monosodium glutamate (MSG), maltol, ethyl maltol, polysorbate-80 (P80), diacetyl tartaric acid ester of mono- and diglycerides (DATEM), soy lecithin, and sodium dodecyl sulfate (SDS). Microbial growth was monitored by optical density at 600 nm over 48 hours. Based on growth dynamics, representative concentrations were selected for downstream multi-omics analyses. Microbial pellets were collected for shotgun metagenomic sequencing, and proteins were prepared using the single-pot solid-phase-enhanced sample preparation (SP3) protocol for metaproteomic analysis.

Maltol, ethyl maltol, SDS, DATEM, and soy lecithin at daily doses inhibited microbial growth in a dose dependent manner, with effects detectable within 6 hours. DATEM and soy lecithin showed biphasic responses with early inhibition followed by partial recovery. Preliminary metaproteomic analysis revealed a clear separation of fecal microbiota derived protein profiles between the MSG and control groups, with increased abundance of proteins involved in glutamate metabolism, including glutaconyl-CoA decarboxylase subunit alpha and NAD-specific glutamate dehydrogenase. In contrast, the abundance of glutamine synthetase was reduced, indicating a shift in microbial glutamate utilization and nitrogen metabolism. These findings suggest functional alterations in the gut microbiota despite preserved overall growth.

Several commonly used food additives significantly affected gut microbiome growth dynamics. Although MSG and P80 did not inhibit overall bacterial growth, metaproteomic analysis revealed alterations in microbial protein abundance and functional profiles, highlighting potential functional impacts of food additives on the gut microbiota.