Abstract: This study aimed to analyze the factors that influence the reduction of sodium selenite by Lactobacillus plantarum to form selenium nanoparticles and to compare the biological activity of selenium nanoparticles with different particle sizes. We selected strain WZ8 capable of tolerating sodium selenite from 13 strains of L. plantarum isolated from traditional fermented foods. After that, strain WZ8 was used to explore the effects of culture conditions, such as initial pH, temperature, inoculum concentration, the concentration of sodium selenite and stress time on the size of selenium nanoparticles by single factor experiments. In addition, the correlation between the size of selenium nanoparticles and its in vitro antibacterial and antioxidant activity. The results revealed that the size of selenium nanoparticles was affected by the culture conditions. Furthermore, the biological activity test showed that the smaller the size of selenium nanoparticles was, the stronger the bacteriostatic activities were against Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Listeria monocytogene. Selenium nanoparticles with different sizes had different total reducing powers and scavenging capacities against 1,1-diphenyl-2-picryhydrazyl (DPPH), 2,2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) cation and hydroxyl radicals.

Key words: Lactobacillus plantarum; size of selenium nanoparticles; culture condition; antibiotics activity; antioxidation activity