Incredible edible selenium nanoparticles produced by food-grade microorganisms

Abstract

Background: Microorganisms commonly employed in food industry, such as Lactobacillus plantarum and Saccharomyces cerevisiae, are also excellent natural nanotechnologists. They reduce selenite (SeO3 2- ) to form nanoparticles of red selenium (Se0 ) of exceptional quality and with interesting physical and (bio-)chemical properties. Objectives: The production of these nanoparticles has been studied in several relevant microorganisms to gain a better picture of the overall properties and quality of these particles, possible differences between producers, ease of production and, in particular, biological activity. Methods: Several common microorganisms, namely L. plantarum, S. cerevisiae and Escherichia coli have been cultured under standard conditions and 1mM concentrations of SeO3 2- have been converted to red particles of elemental selenium. These particles have been characterized extensively with respect to uniformity, size, shape, consistency and, in particular, biological activity against infectious microbes. Results: Highly uniform amorphous spherical particles of 100 nm to 200 nm in diameter could be produced by several microorganisms, including Lactobacillus. Although originating in bacteria and yeast, these particles exhibit antimicrobial activity when employed at concentrations of around 100 µM. This activity may in part be due to the inherent chemistry of selenium and /or of the protein coating of the particles. Interestingly, yeast also forms larger rod-like structures. These micro-needles with around 85 nm in diameter and up to 3 µm in length exhibit considerable antibacterial activity, possibly resulting from additional, physical interactions with cellular structures. Conclusion: Common microorganisms traditionally employed in the preparation of food produce nanoparticles of selenium which may be harvested and explored as natural antimicrobial agents or antioxidants. These particles provide a fine example of and lead for natural nanotechnology with biological activity and applications in food and food supplementation, medicine, agriculture and cosmetics.