Effect of TiO₂ on Selected Pathogenic and Opportunistic Intestinal Bacteria

Food-grade titanium dioxide (TiO₂) containing a nanoparticle fraction (TiO₂ NPs-nanoparticles) is widely used as a food additive (E171 in the EU). In recent years, questions concerning its effect on the gastrointestinal microbiota have been raised. In the present study, we examined interactions between bacteria and TiO₂. The study involved six pathogenic/opportunistic bacterial strains and four different-sized TiO₂ types: three types of food-grade E171 compounds and TiO₂ NPs (21 nm). Each bacterial strain was exposed to four concentrations of TiO₂ (60, 150, 300, and 600 mg/L TiO₂). The differences in the growth of the analyzed strains, caused by the type and concentration of TiO₂, were observed. The growth of a majority of the strains was shown to be inhibited after exposure to 300 and 600 mg/L of the food-grade E171 and TiO₂ NPs.