Effects of food-grade inorganic nanoparticles on the probiotic properties of Lactobacillus plantarum and Lactobacillus fermentum

Abstract Inorganic nanoparticles (NPs), such as silica (SiO2), zinc oxide (ZnO), and silver (Ag) NPs, are often added to food products and food packaging materials through which they can be ingested and passed into the gastrointestinal tract. The aim of this study was to investigate the amounts of adsorbed inorganic NPs and the antibacterial effects of different doses of these NPs on Lactobacillus plantarum (L. plantarum) and Lactobacillus fermentum (L. fermentum). Transmission electron microscopy (TEM) showed that inorganic NPs change the morphology of probiotics and destroy their cell membranes; this finding was further confirmed by confocal laser scanning microscopy (CLSM). After ZnO NPs adsorbed to L. plantarum, the mass change (Δm) reached 169.3 ng/cm2 according to quartz crystal microbalance with dissipation (QCM-D) measurements. The loss of intracellular nucleic acid from L. fermentum with NPs followed a dose-dependent trend. After treatment with NPs, the cell membrane permeability of L. plantarum increased. These results suggest that food-grade NPs have bactericidal effects on L. plantarum and L. fermentum.