Bioconversion of inorganic selenium to less toxic selenium forms by microbes: A review

Abstract

In recent years, microbial conversion of inorganic selenium into an efficient and low-toxic form of selenium has attracted much attention. With the improvement of scientific awareness and the continuous progress of nanotechnology, selenium nanoparticles can not only play the unique functions of organic selenium and inorganic selenium but also have higher safety, absorption and biological activity than other selenium forms. Therefore, the focus of attention has gradually shifted beyond the level of selenium enrichment in yeast to the combination of biosynthetic selenium nanoparticles (BioSeNPs). This paper primarily reviews inorganic selenium and its conversion to less toxic organic selenium and BioSeNPs by microbes. The synthesis method and potential mechanism of organic selenium and BioSeNPs are also introduced, which provide a basis for the production of specific forms of selenium. The methods to characterize selenium in different forms are discussed to understand the morphology, size and other characteristics of selenium. In general, to obtain safer and higher selenium content products, it is necessary to develop yeast resources with higher selenium conversion and accumulation.

Superoxide Dismutase Catalyzed Size-Adjustable Selenium Nanoparticles in Saccharomyces boulardii

“…7 Bacteria and fungi metabolize selenite to organic selenium and BioSeNPs through various enzymatic processes, and BioSeNPs can be generated when sodium selenite is present at a high concentration. 8,9 To defend against excessive toxic chemicals and eliminate high surface energy, defensive proteins, such as bacterial elongation flagellin (FliC), can assemble SeNPs by coating the surface of the nanoparticles and promoting stability. 7 These coating proteins, named protein coronas, are key components that direct biological activity; can change the size, morphology, stability, surface charge, and resistance to aggregation of nanoparticles; reduce the toxicity of nanoparticles; and provide a practicable drug delivery system for biomedical applications.…”

“…However, they are more unstable than biologically synthesized SeNPs (BioSeNPs), particularly under highly ionic, acidic, and alkaline conditions, because of their thermodynamic instability and high surface energy, thus limiting their applications . Bacteria and fungi metabolize selenite to organic selenium and BioSeNPs through various enzymatic processes, and BioSeNPs can be generated when sodium selenite is present at a high concentration. , To defend against excessive toxic chemicals and eliminate high surface energy, defensive proteins, such as bacterial elongation flagellin (FliC), can assemble SeNPs by coating the surface of the nanoparticles and promoting stability . These coating proteins, named protein coronas, are key components that direct biological activity; can change the size, morphology, stability, surface charge, and resistance to aggregation of nanoparticles; reduce the toxicity of nanoparticles; and provide a practicable drug delivery system for biomedical applications. , In addition, the composition of the protein corona depends on the type of biological source and nanoparticle and is believed to be biologically related to the nanoparticles, which affects circulation time, stability, and cellular interaction/uptake, thus having a significant impact on their function .…”

Catechins and Selenium Species—How They React with Each Other

“…The biological activities of selenium are determined not only by the intake dose but also by its chemical form. Compared with inorganic selenium species (selenite and selenate), its organic compounds, such as selenoaminoacids, are less toxic and have greater bioavailability [23]. The newest investigated Se form, selenium nanoparticles (SeNPs), has the advantages of high biological activity and low toxicity.…”