[Characteristics and antimicrobial activities of selenium nanoparticles biosynthesized by selenium-tolerant yeast]

Selenium is an essential trace element for the human body, enhancing the body resistance to a variety of diseases induced by oxidative stress. Selenium nanoparticles (SeNPs) possess advantages such as low toxicity and broad biocompatibility. In order to screen for a strain with high efficiency in synthesizing SeNPs, we investigated the selenium tolerance and SeNPs synthesis capacities of three selenium-tolerant yeast strains and the in vitro antioxidant activities and antimicrobial activities of the synthesized SeNPs. Furthermore, we characterized SeNPs synthesized by strain M16-28 with the best performance. The results indicated that strain M16-28 was capable of tolerating 300 mmol/L Na₂SeO₃, with a SeNPs synthesis capacity of 1 018.92 μg/mL, which was 2.86 times that of strain M1. The in vitro antioxidant experiments indicated that the synthesized SeNPs exhibited the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate of 65.7%, the hydroxyl radical scavenging rate of 57.5%, and the reducing power of 0.77. The antimicrobial experiments indicated that the synthesized SeNPs displayed significantly stronger inhibitory effects against Gram-positive bacteria than against Gram-negative bacteria, and they had a significant inhibitory effect on the pathogenic microorganisms causing stem rot of Lycium barbarum. The SeNPs synthesized by the three yeast strains exhibited an inhibition rate higher than 90% against Fusarium spp., and a lower inhibition rate against Alternaria alternata.The SeNPs produced by strain M16-28 exhibited the highest antimicrobial activity, with an inhibition rate of (66.53±1.37)%. Characterization results indicated that SeNPs were closely arranged, encapsulated by polysaccharides, and negatively charged, with a size ranging from 190 nm to 390 nm and the zeta potential of -7.87 mV. In conclusion, strain M16-28 demonstrates ideal performance of synthesizing SeNPs, and the capacity for selenium enrichment is positively correlated with the ability to synthesize SeNPs. This study provides a potential microbial resource for the efficient synthesis of SeNPs.