Development and application of a new biological nano-selenium fermentation broth based on Bacillus subtilis SE201412

Abstract

In order to improve the functionality and additional value of agricultural products, this study developing nano-selenium fermentation broth and established a new application strategy of bio-nano-selenium by screening and identifying selenium-rich microorganisms. We isolated a new strain from tobacco waste and named it Bacillus subtilis SE201412 (GenBank accession no. OP854680), which could aerobically grow under the condition of 66,000 mg L−1 selenite concentration, and could convert 99.19% of selenite into biological nano-selenium (BioSeNPs) within 18 h. Using strain SE201412, we industrially produced the different concentrations of fermentation broth containing 5000–3000 mg L−1 pure selenium for commercial use. The synthesized selenium nanoparticles (SeNPs) were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nanoparticle tracking analysis (NTA). TEM and SEM results showed that SeNPs were distributed outside cells. NTA assay of fermentation broth indicated that the nanoparticles were spherical with an average particle size of 126 ± 0.5 nm. Toxicity test revealed that the median lethal dose (LD50) of the fermentation broth to mice was 2710 mg kg−1, indicating its low toxicity and high safety. In addition, we applied BioSeNP fermentation broth to rice and wheat through field experiments. The results showed that the application of fermentation broth significantly increased the total selenium content and organic selenium percentage in rice and wheat grains. Our findings provide valuable reference for the development of BioSeNPs with extensive application prospects.

Selenium Nanoparticles: Green Synthesis and Biomedical Application

“…The following hypotheses of SeNP export from the cell can be found in the literature: (1) the bubbles' formation on the outer membrane (membrane vesicles), occurring in response to stress by encapsulating various harmful substances in the bubbles of a lipid bilayer membrane for removal outside the cell; (2) secretion due to the specialized proteins (for example, the SefA protein in Thauera elenatis) [53,54]. Extracellular SeNP synthesis was shown for Pseudomonas alcaligenes [55], Enterococcus faecalis [56], Bacillus subtilis [57], on the membrane surface of bacteria isolated from wastewater from glass factories [58], etc. Such synthesis is preferable to intracellular because it does not require further isolation of nanoparticles from the cell.…”

“…However, nanoparticles with a smaller diameter are of the greatest interest for further biomedical use because SeNPs with a particle size of less than 200 nm easily penetrate into cells, participate in metabolic processes, and, thus, exhibit higher biological activity [57]. The initial selenite concentration for the synthesis is also important: an increase in the sodium selenite concentration in the medium led to the formation of small amounts of bacterial SeNPs [57].…”

Arsenite Mediates Selenite Resistance and Reduction in Enterobacter sp. Z1, Thereby Enhancing Bacterial Survival in Selenium Environments

“…Selenium (Se) is an essential trace element for humans and animals and has an uneven regional distribution . Approximately 15% of the global population suffers from Se deficiency. , Owing to its relatively limited occurrence and uneven dispersion within the earth’s crust, Se ranks as the 69th element in terms of abundance. , The primary chemical forms of Se include selenate [Se­(VI)], selenite [Se­(IV)], and Se nanoparticles (SeNPs). , Among these variants, Se­(IV) exhibits the maximum cytotoxicity, followed by Se­(VI), and SeNPs demonstrate minimal phytotoxic effects. − The bioactivity and stability of SeNPs surpass those of other Se species, thus rendering them a desirable choice for agriculture production. − Consequently, an increasing number of studies have focused on reducing Se into SeNPs. , Several bacterial proteins reportedly possess Se­(IV) reduction capabilities, including the ferredoxin protein FesR found in Alishewanella sp. WH16-1, respiratory Se­(IV) reductase complex SrrABC identified in the Bacillus selenitireducens strain MLS10, glutathione reductase GorA discovered in the Pseudomonas stutzeri strain TS44, and a potential periplasm molybdenum oxidoreductase named SerT detected in the Comamonas testosteroni strain S44 …”