In Vitro Effects of Twelve Food Additives on Gut Microbiome and Its Fibre Fermentation Capacity in Adults with Crohn’s Disease in Remission and Healthy Controls

<b>Background/Objectives:</b> Animal studies have shown that food additives may adversely affect the gut microbiome. However, the effect of food additives on the microbiome in adults with Crohn's disease (CD) remains less explored. This study investigated the impact of food additives on gut microbiome and fibre fermentation capacity in adults with CD and healthy controls (HCs) using in vitro faecal fermentations. <b>Methods:</b> Faeces from 6 HCs and 6 patients with CD in clinical remission (Harvey Bradshaw Index < 5) were used for in vitro fermentation of a fibre mix with one of 12 food additives (calcium propionate, carboxymethylcellulose, carrageenan kappa, cinnamaldehyde, maltodextrin, polysorbate-80, potassium sorbate, sodium benzoate, sodium sulphite, titanium dioxide, turmeric, and xanthan gum). Short-chain fatty acids (SCFAs) were measured using gas chromatography, the microbiome was profiled with 16S rRNA amplicon sequencing and total bacterial load was measured with qPCR. <b>Results</b>: Maltodextrin increased acetate production in both groups. In HCs, turmeric increased acetate and butyrate production, sodium sulphite reduced acetate production, and maltodextrin reduced butyrate production. Microbiome Shannon α-diversity increased with titanium dioxide (both groups), and with carrageenan kappa only in patients with CD. In both groups, the addition of maltodextrin and polysorbate-80 induced significant shifts in microbiome structure (β-diversity). Significant shifts were seen with maltodextrin (HC: R² = 6.8%, <i>p</i> = 0.001; CD: R² = 5.1%, <i>p</i> = 0.004) and sodium sulphite (HC: R² = 6.9%, <i>p</i> = 0.001). Maltodextrin significantly decreased the estimated absolute abundance of <i>Escherichia-Shigella</i> in patients CD; sodium benzoate, potassium sorbate, and calcium propionate did so in HCs. <i>Faecalibacterium</i> decreased in the presence of polysorbate-80 in the HC and CD groups, as well as in the presence of maltodextrin in the CD group. Total bacterial load decreased with polysorbate-80, potassium sorbate, maltodextrin and calcium propionate in both groups. Xanthan gum decreased total bacterial load in HCs. <b>Conclusion:</b> Certain food additives significantly affected fibre fermentation capacity and microbiome structure, with only modest differences observed according to participants' health status.