Bioactivity assessment of selenium nanoparticles biosynthesized by Akkermansia muciniphila

Akkermansia muciniphila (AM) exhibits a capacity for the biosynthesis of selenium nanoparticles (SeNPs); however, the biological activities of these microbially derived nanoparticles remain unknown. This study investigated how key cultivation parameters influence the particle size distribution of AM-derived SeNPs. Furthermore, transcriptomic analysis was employed to elucidate the underlying biosynthetic mechanisms of SeNPs, and SeNPs representing distinct size profiles were selected for bioactivity evaluation. The results demonstrated that the temperature, initial medium pH, carbon source, and the timing and concentration of sodium selenite addition critically dictate SeNPs size. In a single-factor experiment, lactose supplementation yielded the smallest nanoparticles (Min-SeNPs; 105.0 ± 0.9 nm), whereas an initial pH of 7.0 produced the largest (Max-SeNPs; 140.0 ± 0.9 nm). Transcriptomic profiling of selenite-exposed AM revealed significant enrichment in KEGG pathways associated with oxidative phosphorylation, protein export, and bacterial secretion systems. Notably, the marked upregulation of genes encoding oxidoreductases highlighted that they may play a key role in the biogenesis of SeNPs. In vitro bioactivity assays indicated that neither Min-SeNPs nor Max-SeNPs exhibited good antibacterial efficacy against foodborne pathogens, except Shigella sonnei. Conversely, both SeNPs formulations effectively induced excessive reactive oxygen species (ROS) generation in CT-26 cells, resulting in significant cytotoxicity. Collectively, these findings demonstrate that the particle size of AM-synthesized SeNPs can be modulated via cultivation optimization. The resulting SeNPs exhibit biological activities, highlighting their promising potential for applications in functional foods and related biotechnological sectors.