The Preparation And Optimization Of Biological Selenium Nanoparticles

Selenium (Se) is an essential element for human physiological activity. Neither selenium excess nor selenium deficiency would be beneficial to biological health. Most of the countrys and reagions in the world, especially china were in the lack of selenium supplyment from food. The development of the health food rich of selenium would gain a promising expectation because of the huge-but long-term market-demand of this kind of selenium food.Selenium nanoparticles (SeNPs) is one of the type of elemental selenium with nano-size. SeNPs possess the ability to supply selenium to human body with low toxicity. The bio-safety of selenium to humanbody would be improved to a certain extent by selenium nanoparticles. Thus the study on selenium nanoparticles becomes one of the most important prospects when developing selenium supplement with high efficiency but limited toxic effects.In this paper, the Bacillus amyloliquefaciens was elected to be the experimental strains to synthesize the biosynthetic selenium nanoparticles (BioSeNPs) with its reduction ability for the reduction of SeO32-to elemental selenium nanoparticles (SeNPs). Meantime, this study investigated the role of EPS in synthesizing BioSeNPs, BioSeNPs were covered by an organic layer contained proteins component, which were responsible and long term stabilization of BioSeNPs. In this paper, we investigate the effects of reaction time, temperature, pH, initial concentration of bacteria, rotation speed, liquid volume on selenium nanoparticles conversion rates in order to find the best experimental conditions. However, the conversion rate of SeNPs was relatively low by the current biological method. Therefore, we try to find a way to improve the properties of proteins and other component functional groups in extracellular polymeric substances (EPS) of Bacillus amyloliquefaciens in order to improve the conversion rate of SeNPs. In this paper, we use the fetal bovine serum (FBS) or chitosanas theadditional agent, which could promote cell growth, enhance the biological activity of the enzyme, and thus increase the reaction rate, improve the conversion rate of SeNPs, optimizing selenium nanoparticles traits and stabilize the SeNPs. This study investigated the effect of FBS and chitosan on component and structure of EPS. FT-IR spectroscopy and XPS measurements confirmed the increasing of proteins and carbohydrates by additional FBS and chitosan in Bacillus amyloliquefaciens, which would promote the cell activities, conversion efficiency and reaction rate of BioSeNPs. XRD and EDX analysis showed that this synthesis method yielded a large amount of stable colloidal spherical BioSeNPs with high crystallinity in the presence of FBS and chitosan. Furthermore, compared with BioSeNPs, FBS-BioSeNPs had a higher ζ-potential and iso-electric point that can improve the stability of BioSeNPs.