Accumulation and metabolism of selenium by yeast cells

Selenite Reduction by Proteus sp. YS02: New Insights Revealed by Comparative Transcriptomics and Antibacterial Effectiveness of the Biogenic Se0 Nanoparticles

Biotransformation of selenite by microorganisms is an effective detoxification (in cases of dissimilatory reduction, e.g., to Se⁰) and assimilation process (when Se is assimilated by cells). However, the current knowledge of the molecular mechanism of selenite reduction remains limited. In this study, a selenite-resistant bacterium was isolated and identified as Proteus sp. YS02. Strain YS02 reduced 93.2% of 5.0 mM selenite to selenium nanoparticles (SeNPs) within 24 h, and the produced SeNPs were spherical and localized intracellularly or extracellularly, with an average dimension of 140 ± 43 nm. The morphology and composition of the isolated and purified SeNPs were characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectrometry, and Fourier transform infrared (FTIR) spectroscopy. FTIR spectroscopy indicated the presence of proteins, polysaccharides, and lipids on the surface of the isolated SeNPs. Furthermore, the SeNPs showed excellent antimicrobial activity against several Gram-positive and Gram-negative pathogenic bacteria. Comparative transcriptome analysis was performed to elucidate the selenite reduction mechanism and biosynthesis of SeNPs. It is revealed that 197 genes were significantly upregulated, and 276 genes were significantly downregulated under selenite treatment. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that genes associated with ABC transporters, sulfur metabolism, pentose phosphate pathway (PPP), and pyruvate dehydrogenase were significantly enhanced, indicating selenite is reduced by sulfite reductase with PPP and pyruvate dehydrogenase supplying reducing equivalents and energy. This work suggests numerous genes are involved in the response to selenite stress, providing new insights into the molecular mechanisms of selenite bioreduction with the formation of SeNPs.

The protective role of selenium against uptake and accumulation of cadmium and lead in white oyster (Pleurotus ostreatus) and pink oyster (Pleurotus djamor) mushrooms

Mushrooms are bioaccumulators and have been used to produce Se-enriched foods. However, these fungi can also bioaccumulate potentially toxic metals, producing food dangerous to human health. It is known that co-exposure to Se plays a protective role against metal accumulation and toxicity in some organisms due to its antioxidant properties. Thus, this study aimed to evaluate the protective effect of Se(IV) and Se(VI) on elemental uptake and accumulation as well as proteins and protein-bound Se, Cd, and Pb distribution in Pleurotus mushrooms. Pink oyster and white oyster mushrooms showed high ability to bioaccumulate Se (19-205 µg g^-1), Cd (4.5 to 18.8 µg g^-1), and Pb (1.6 to 7.0 µg g^-1). Growth substrate supplementation with Se(IV) or Se(VI) decreased the Cd total concentration in mushrooms by 4 to 89%, while Se(VI) increased the Pb total concentration by 9% to 187%, compared to growth in absence of Se. It was found that despite molecular weights distributions of mushrooms grown on Se(IV) and Se(VI)-supplemented substrates being similar, Se(VI) supplementation favoured Se interaction with proteins of medium molecular weight (17-44 kDa), when compared to supplementation with Se(IV). Therefore, we propose the supplementation of growth substrates with Se(VI) to reduce eventual Cd accumulation and produce Se-enriched oyster mushrooms.

Assessment of hexavalent chromium (VI) biosorption competence of indigenous Aspergillus tubingensis AF3 isolated from bauxite mine tailing

The intention of this research was to find the most eminent metal tolerant and absorbing autochthonous fungal species from the waste dump of a bauxite mine. Out of the 4 (BI-1, BI-II, BI-III, and BI-IV) predominant isolates, BI-II had an excellent metal tolerance potential against most of the metals in the subsequent order: Cr(VI) (1500), Cu(II) (600), Pb(II) (500), and Zn(II) (500-1500 μg mL^-1). BI-II had shown tolerance to Cr(VI) up to 1500 mg L^-1. The excellent metal tolerant isolate was characterized and identified as Aspergillus tubingensis AF3 through 18S rRNA sequencing method and submitted to GenBank and received an accession number (MN901243). A. tubingensis AF3 had the efficiency to absorb Cr(VI) and Cu(II) at <70 & 46.3% respectively under the standard growth conditions. Under the optimized conditions (25 °C, pH 7.0, 0.5% of dextrose, and 12 days of incubation), A. tubingensis AF3 absorbed 74.48% of Cr(VI) in 12 days (reduction occurred as 822.3, 719.13, 296.66, and 255.2 mg L^-1 of Cr(VI) on the 3^rd, the 6^th, the 9^th and the 12^th day, respectively). The adsorbed metal was sequestered in the mycelia of the fungus in a precipitated form; it was confirmed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray analysis (EDX) analyses. The possible biosorption mechanisms were analyzed by Fourier-Transform Infrared Spectroscopy (FTIR) analysis, the results showed the presence of N-H primary amines (1649.98 cm^-1) and Alkanes (914.30 cm^-1) in the cell wall of the fungus, while being treated with Cr(VI) they supported and enhanced the Cr(VI) absorption. The entire results concluded that the biomass of A. tubingensis AF3 had the potential to absorb a high concentration of Cr(VI).

Purification and comparative study of bioactivities of a natural selenized polysaccharide from Ganoderma Lucidum mycelia

The development of selenized polysaccharides is a promising strategy for the dietary selenium supplementation. The purpose of this research is to determine the influence of selenium on the structure and bioactivity of a polysaccharide fraction (MPN) isolated from Ganoderma lucidum mycelia. After biological selenium enrichment, the selenium content in the selenized polysaccharide (SeMPN) was 18.91 ± 1.8 μg/g. SeMPN had a slightly lower molecular weight than MPN, but the carbohydrate content and monosaccharide composition remained identical. Additionally, the band at 606 cm^-1 in MPN changed to 615 cm^-1 in SeMPN as revealed by FT-IR spectra. No significant changes were observed in the types and ratios of glycosidic linkages, as determined by NMR spectroscopy. Extracellular and intracellular antioxidant assays demonstrated that SeMPN was more effective than MPN in scavenging free radicals, inhibiting AAPH-induced erythrocyte hemolysis, and protecting catalase (CAT) and glutathione peroxidase (GSH-Px) activity in H₂O₂-injured PC12 cells. Additionally, SeMPN had a higher increase effect on RAW 264.7 cells's pinocytic and phagocytic capacity, as well as their production of NO, TNF-α, and IL-6. SeMPN could be as potential functional selenium supplementation.

Recent development in Se-enriched yeast, lactic acid bacteria and bifidobacteria

Endemic selenium (Se) deficiency is a major worldwide nutritional challenge. Organic Se can be synthesized through physical and chemical methods that are conducive to human absorption, but its high production cost and low output cannot meet the actual demand for Se supplementation. Some microbes are known to convert inorganic Se into organic forms of high nutritional value and Se-enriched probiotics are the main representatives. The aim of the present review is to describe the characteristics of Se-enriched yeast, lactic acid bacteria, bifidobacteria and discuss their Se enrichment mechanisms. Se products metabolized by Se-enriched probiotics have been classified, such as Se nanoparticles (SeNPs) and selenoprotein, and their bioactivities have been assessed. The factors affecting the Se enrichment capacity of probiotics and their application in animal feed, food additives, and functional food production have been summarized. Moreover, a brief summary and the development of Se-enriched probiotics, particularly their potential applications in the field of biomedicine have been provided. In conclusion, Se-enriched probiotics not just have a wide range of applications in the food industry but also have great potential for application in the field of biomedicine in the future.

Evolutionary and functional analyses demonstrate conserved ferroptosis protection by Arabidopsis GPXs in mammalian cells

Species have evolved unique mechanisms to combat the effects of oxidative stress inside cells. A particularly devastating consequence of an unhindered oxidation of membrane lipids in the presence of iron results in cell death, known as ferroptosis. Hallmarks of ferroptosis, including peroxidation of polyunsaturated fatty acids, are conserved among animals and plants, however, early divergence of an ancestral mammalian GPX4 (mGPX4) has complicated our understanding of mechanistic similarities between species. To this end, we performed a comprehensive phylogenetic analysis and identified that orthologous Arabidopsis GPXs (AtGPXs) are more highly related to mGPX4 than mGPX4 is to other mammalian GPXs. This high degree of conservation suggested that experimental substitution may be possible. We, therefore, ectopically expressed AtGPX1-8 in ferroptosis-sensitive mouse fibroblasts. This substitution experiment revealed highest protection against ferroptosis induction by AtGPX5, as well as moderate protection by AtGPX2, -7, and -8. Further analysis of these cells revealed substantial abatement of lipid peroxidation in response to pharmacological challenge. The results suggest that the presence of ancestral GPX4 resulted in later functional divergence and specialization of GPXs in plants. The results also challenge a strict requirement for selenocysteine activity and suggest thioredoxin as a potent parallel antioxidant system in both plants and mammals.

Compilation of selenium metabolite data in selenized yeasts

Selenium-enriched yeast has long been recognized as an important nutritional source of selenium and studies have suggested that supplementation with this material provides chemo-preventative benefits beyond those observed for selenomethionine supplementation, despite the fact that selenomethionine accounts for 60-84% of the total selenium in selenized yeasts. There is much ongoing research into the characterization of the species comprising the remaining 16-40% of the selenium, with nearly 100 unique selenium-containing metabolites identified in aqueous extracts of selenized yeasts (Saccharomyces cerevisiae). Herein, we discuss the analytical approaches involved in the identification and quantification of these metabolites, and present a recently created online database (DOI: 10.4224/40001921) of reported selenium species along with chemical structures and unique mass spectral features.

Tellurium: A Rare Element with Influence on Prokaryotic and Eukaryotic Biological Systems

Metalloid tellurium is characterized as a chemical element belonging to the chalcogen group without known biological function. However, its compounds, especially the oxyanions, exert numerous negative effects on both prokaryotic and eukaryotic organisms. Recent evidence suggests that increasing environmental pollution with tellurium has a causal link to autoimmune, neurodegenerative and oncological diseases. In this review, we provide an overview about the current knowledge on the mechanisms of tellurium compounds' toxicity in bacteria and humans and we summarise the various ways organisms cope and detoxify these compounds. Over the last decades, several gene clusters conferring resistance to tellurium compounds have been identified in a variety of bacterial species and strains. These genetic determinants exhibit great genetic and functional diversity. Besides the existence of specific resistance mechanisms, tellurium and its toxic compounds interact with molecular systems, mediating general detoxification and mitigation of oxidative stress. We also discuss the similarity of tellurium and selenium biochemistry and the impact of their compounds on humans.

Effect of Selenium on the Growth and Lipid Accumulation of Yarrowia lipolytica Yeast

Nowadays, there is an increase attention on the effect of selenium (Se) on metabolic processes of microorganisms. Strains belonging to the genus of Yarrowia are of great biotechnological interest for various industries. In this study, we evaluated the effect of 10 mg/L of Se on the growth and lipid production of two Yarrowia lipolytica strains: the ACA DC 50109 and one more with increased oleagenicity, derived after ALE methodology (referred here as Y. lipolytica ALE_70). The presence of Se in the growth medium negatively affected both cell mass production and total lipid accumulation, for both Y. lipolytica strains. Fractionation of total lipids showed an inhibition on neutral lipid (NL) synthesis and consequently, an increase of polar lipids (glycolipids plus sphingolipids, and phospholipids) on the lipids of the Se-enriched ACA DC 50109 strain; however, the NL/polar ratio of the Se-enriched ALE_70 indicated that Se, apart from the inhibition of NL synthesis, provoked also the accumulation of polar lipids in this strain. In addition, the fatty acid (FA) composition was differently affected by Se. Se-enriched total lipids of the ALE_70 strain were enriched in linoleic acid (C18:2 n-6), which resulted in increase of the unsaturated index. On the other hand, Se-enriched lipids of the ACA DC 50109 strain were more saturated, as the percentage of palmitic (C16:0) and stearic (C18:0) acids increased in the total FAs. Moreover, it seems that Se influenced the activity or the expression of desaturases and elongase in both strains. Finally, the supplementation of growth medium with Se affected cell morphology, as well as the size and distribution of lipid droplets inside the yeast cells. According to our opinion, Se caused stress conditions and the consequence of that was the occurrence of metabolic disorders that affected cell mass, lipid content, and/or morphological structures. The results of the present study suggest that further research should be carried out to understand the background of the lipogenesis process in yeast cells cultured under stress conditions.

NAD(P)H-dependent thioredoxin-disulfide reductase TrxR is essential for tellurite and selenite reduction and resistance in Bacillus sp. Y3

Microbial reduction of selenite [Se(IV)] and tellurite [Te(IV)] to Se(0) and Te(0) can function as a detoxification mechanism and serve in energy conservation. In this study, Bacillus sp. Y3 was isolated and demonstrated to have an ability of simultaneous reduction of Se(IV) and Te(IV) during aerobic cultivation, with reduction efficiencies of 100% and 90%, respectively. Proteomics analysis revealed that the putative thioredoxin disulfide reductase (TrxR) and sulfate and energy metabolic pathway proteins were significantly upregulated after the addition of Se(IV) and Te(IV). qRT-PCR also showed an increased trxR transcription level in the presence of Se(IV) and Te(IV). Compared with a wild-type Escherichia coli strain, the TrxR-overexpressed E. coli strain showed higher Se(IV) and Te(IV) resistance levels and reduction efficiencies. Additionally, the TrxR showed in vitro Se(IV) and Te(IV) reduction activities when NADPH or NADH were present. When NADPH was used as the electron donor, the optimum conditions for enzyme activities were pH 8.0 and 37°C. The Km values of Te(IV) and Se(IV) were 16.31 and 2.91 mM, and the Vmax values of Te(IV) and Se(IV) were 12.23 and 11.20 µM min-1 mg-1, respectively. The discovery of the new reductive enzyme TrxR enriches the repertoire of the bacterial Se(IV) and Te(IV) resistance and reduction mechanisms. Bacillus sp. Y3 can efficiently reduce Se(IV) and Te(IV) simultaneously. Strain Y3 provides potential applications for selenite and tellurite bioremediation. The TrxR enzyme shows high catalytic activity for reducing Se(IV) and Te(IV). The discovery of TrxR enriches the bacterial Se(IV) and Te(IV) reduction mechanisms.

In situ synthesis of silver or selenium nanoparticles on cationized cellulose fabrics for antimicrobial application

In this study, we developed a method to prepare inorganic nanoparticles in situ on the surface of cationized cellulose using a rapid microwave-assisted synthesis. Selenium nanoparticles (SeNPs) were employed as a novel type of antimicrobial agent and, using the same method, silver nanoparticles (AgNPs) were also prepared. The results demonstrated that both SeNPs and AgNPs of about 100 nm in size were generated on the cationized cellulose fabrics. The antibacterial tests revealed that the presence of SeNPs clearly improved the antibacterial performance of cationized cellulose in a similar way as AgNPs. The functionalised fabrics demonstrated strong antibacterial activity when assessed using the challenge test method, even after repeated washing. Microscopic investigations revealed that the bacterial cells were visually damaged through contact with the functionalised fabrics. Furthermore, the functionalised fabrics showed low cytotoxicity towards human cells when tested in vitro using an indirect contact method. In conclusion, this study provides a new approach to prepare cationic cellulose fabrics functionalised with Se or Ag nanoparticles, which exhibit excellent antimicrobial performance, low cytotoxicity and good laundry durability. We have demonstrated that SeNPs can be a good alternative to AgNPs and the functionalised fabrics have great potential to serve as an anti-infective material.

Selenium-Containing Proteins/Peptides from Plants: A Review on the Structures and Functions

Selenium is an essential microelement required for biological processes. Traditional selenium supplements (selenite and selenomethionine mainly) remain concerns due to toxicity and bioavailability. In recent decades, biofortification strategies have been applied to produce selenium-enriched edible plants to address the challenges of superior nutritional quality requirements. Plant-derived selenium-containing proteins/peptides offer potential health benefits beyond the basic nutritional requirements of Se. Highly nucleophilic seleno-amino acids, special peptide sequences, and favorable bioavailability contribute to the biological activities of selenium-containing proteins/peptides, such as antioxidant, antihypertensive, anti-inflammatory, and immunomodulatory effects. However, their applications on a commercial scale are insufficient owing to the complexity of purification and identification techniques and the sparse information on bioavailability and metabolism. In this review, selenium status, structural features, bioactivities, structure-activity relationships, and bioavailability, as well as the mechanisms underlying the bioactivities and metabolism of plant-derived selenium-containing proteins/peptides, are summarized and discussed for their nutraceutical use.

A New Approach for the Production of Selenium-Enriched and Probiotic Yeast Biomass from Agro-Industrial by-Products in a Stirred-Tank Bioreactor

The production of biomolecules using agro-industrial by-products as feedstock is a growing trend worldwide. Selenium (Se) is a trace element essential for health, and the Se-enrichment of yeast biomass can enhance its benefits. This study investigated the feasibility of the production of Saccharomyces cerevisiae Se-enriched biomass using a medium composed of corn bran and soybean bran acid hydrolysates as carbon and nitrogen sources in a stirred-tank reactor. After hydrolysis, hydrolysates presented complex composition and high concentrations of sugars, proteins, and minerals. The use of a stirred-tank bioreactor leads to the production of 9 g/L S. cerevisiae biomass enriched with 236.93 μg/g Se, and 99% cell viability. Likewise, the combination of sugarcane molasses and soybean bran hydrolysate was effective for cell growth of a probiotic strain of S. cerevisiae with a 24.08% β-glucan content. The results demonstrated that starchy acid hydrolysates are low-cost and efficient substrates for the production of yeast biomass and derivate products and may contribute to further studies for a sustainable development of biorefinery technologies.

Selenium accumulation, speciation, and its effect on nutritive value of Flammulina velutipes (Golden needle mushroom)

Flammulina velutipes is one of the most popular edible mushrooms worldwide. A selenium-biofortification method for its fruiting body was developed using selenite. This study investigated the selenium content, distribution, speciation and the effect of selenium on mushroom growth, nutritive value, and mineral accumulation. Results showed that F. velutipes accumulated nearly 108 μg/g of organic selenium under treatment with 20 μg/g selenite, which accounts for over 97% of total selenium. Most (60-74%) of selenium combined with the protein fraction, whereas 15-21% combined with the polysaccharide fraction. Selenomethionine (56.8%), selenocysteine (22.8%), and methylselenocysteine (17.3%) were the main organic selenium compounds in the fruiting body. Selenium biofortification increased the biomass yield of fruiting body and elevated the content of polysaccharides, proteins, total amino acids, essential amino acids, and several minerals, including iron, calcium, and copper. F. velutipes might become a suitable selenium supplement.

Development of Selenized Lactic Acid Bacteria and their Selenium Bioaccummulation Capacity

Selenized lactic acid bacteria (LAB) represent potentially safe and effective sources of selenium (Se), essential for human health, as lactic acid fermentation improves Se bioavailability and reduces its toxicity. LAB are generally recognized as safe (GRAS) and widely used in fermented dairy products. To facilitate selenized LAB implementation as a functional food, we developed and characterized new Se-enriched strains based on the food industry commercial strains Streptococcus thermophilus CCDM 144 and Enterococcus faecium CCDM 922A as representatives of two LAB genera. We evaluated Se bioaccumulation capacity, Se biotransformation and growth ability in the presence of different sodium selenite concentrations (0–50 mg/L), and antioxidant properties (2, 2-diphenyl-1-picrylhydrazyl (DPPH) method) and cell surface hydrophobicity between Se-enriched and parental strains in vitro. Sodium selenite addition did not negatively influence growth of either strain; thus, 50 mg/L was chosen as the optimal concentration based on strain accumulation capacity. Selenization improved the antioxidant properties of both strains and significantly increased their cell surface hydrophobicity (p < 0.05). To our knowledge, this represents the first report of Se-enriched strain hydrophobicity as well as the first on Se speciation in families Enterococcaceae and Streptococcaceae. Moreover, both tested strains demonstrated good potential for Se-enrichment, providing a foundation for further in vitro and in vivo studies to confirm the suitability of these Se-enriched strains for industrial applications.

Metabolic Response of the Yeast Candida utilis During Enrichment in Selenium

Selenium (Se) was found to inhibit the growth of the yeast Candida utilis ATCC 9950. Cells cultured in 30 mg selenite/L supplemented medium could bind 1368 µg Se/g of dry weight in their structures. Increased accumulation of trehalose and glycogen was observed, which indicated cell response to stress conditions. The activity of antioxidative enzymes (glutathione peroxidase, glutathione reductase, thioredoxin reductase, and glutathione S-transferase) was significantly higher than that of the control without Se addition. Most Se was bound to water-insoluble protein fraction; in addition, the yeast produced 20–30 nm Se nanoparticles (SeNPs). Part of Se was metabolized to selenomethionine (10%) and selenocysteine (20%). The HPLC-ESI-Orbitrap MS analysis showed the presence of five Se compounds combined with glutathione in the yeast. The obtained results form the basis for further research on the mechanisms of Se metabolism in yeast cells.

Adsorptive Removal of Se(IV) by Citrus Peels: Effect of Adsorbent Entrapment in Calcium Alginate Beads

Selenium (Se) contamination in natural waters impacted by anthropogenic activities is becoming a prevalent and widespread problem. Investigation of novel, low-cost, and sustainable food-waste-sourced adsorbents for Se removal has largely been unexplored. Here, we report on the Se(IV) biosorption from a liquid solution using three waste-derived/low-cost biosorbents, namely citrus peels (bare), Ca-alginate gel beads, and Ca-alginate-citrus peels composite beads (Ca-alginate@citrus). The entrapment of citrus peels by Ca-alginate not only provided a structural framework for the citrus peel particles but also preserved the high-efficiency Se(IV) removal property of the citrus peels. From the modeling results, it was established that Se(IV) biosorption followed the fixed-film diffusion model, along with pseudo-second-order kinetics. Investigation of pH impacts along with initial dosing of sorbent/sorbate demonstrated that all of the three biosorbents exhibited optimum biosorption of Se(IV) at pH 6-8, 50-75 mg·L^-1 of Se(IV), and 1-5 mg·L^-1 of biosorbent. Overall, the maximum Se(IV) biosorption capacities were measured to be 116.2, 72.1, and 111.9 mg·g^-1 for citrus peels, Ca-alginate, and Ca-alginate@citrus, respectively, with citrus peels (bare and immobilized) showing among the highest reported values in the literature for Se(IV) adsorption. This work provides a platform for the future development of an efficient filtration system using Ca-alginate@citrus as an inexpensive, novel, and sustainable biosorbent to treat Se(IV) contaminated water.

Selenium biofortification in Hericium erinaceus (Lion's Mane mushroom) and its in vitro bioaccessibility

Hericium erinaceus is a traditional edible mushroom. Selenium (Se) is an essential trace element for humans and other mammals. To develop a Se biofortification strategy for H. erinaceus, the effects of selenate, selenite, and selenomethionine (SeMet) on Se uptake and mushroom growth were investigated. Selenium bioaccessibility and the major Se species present in Se-enriched H. erinaceus were tested in vitro . The H. erinaceus growth was efficiently affected by SeMet than by selenite and selenate. Selenium concentrations in fruiting bodies increased with substrate Se concentration and disturbed accumulation of other microelements. Substrate Se was absorbed and transformed into organic forms. The major Se species in Se-enriched fruiting bodies was SeMet (>63.9%). During in vitro gastrointestinal digestion tests, 51% of total Se was released, and selenocystine (SeCys₂ ) (90%) and Se-methylselenocysteine (MeSeCys) (76%) were more easily digested than SeMet (51%). H. erinaceus is suggested as a novel dietary source of supplemental bioavailable Se.

Population Kinetics and Mechanistic Aspects of Saccharomyces cerevisiae Growth in Relation to Selenium Sulfide Nanoparticle Synthesis

Biosynthesis of nanoparticles (NPs) by microorganisms is a cost- and energy-effective approach. However, how the production of NPs affects the population of producing organism remains as an unresolved question. The present study aimed to evaluate the kinetics of Saccharomyces cerevisiae growth in relation to synthesis of selenium sulfide nanoparticles by using a population model. To this end, the population of S. cerevisiae cells was investigated in terms of colony forming units (CFU) in the presence of the substrate in different time points. Fluctuation of sulfite reductase (SiR) activity, expression of MET5 and MET10 genes, and concentrations of sulfite and selenium were evaluated to support the population findings. CFU values in the test groups were lower than those in the control counterparts. The rise and fall of the SiR activity and MET5 and MET10 gene expression conformed to the variations of CFU values. The rate of reduction in the selenium and sulfite concentrations tended to decrease over the time. In conclusion, the cells population was negatively and positively affected by selenium and sulfite concentrations, respectively. The indirect relationship of the selenium ions concentration in the path analysis revealed that the product, selenium sulfide nanoparticles, caused this drop in S. cerevisiae cells population.

Transcriptomic analysis of selenium accumulation in Puccinellia distans (Jacq.) Parl., a boron hyperaccumulator

Selenium (Se) is present in a wide variety of natural and man-made materials on Earth. Plants are able to tolerate and (hyper)accumulate Se to different extents. In fact, some species can tolerate and accumulate multiple elements. Puccinellia distans (P. distans), weeping alkali grass, is known to hyperaccumulate extreme concentrations of boron and tolerate high levels of salinity, therefore, we investigated the Se accumulation and tolerance capacities of this species. In addition, P. distans' Se tolerance mechanism was studied using a transcriptomic approach. The results of this study indicated that, when grown in a hydroponic system containing 80 or 120 μM Se, P. distans shoots accumulated from 1500 to 2500-fold more Se than plants grown without the element. Thus, P. distans was discovered to be a novel Se accumulator plant. RNA sequencing results and biochemical analyses helped to shed light on the Se tolerance and accumulation mechanism of P. distans. Here, we suggest that upregulation of Se assimilation and stress response genes may be due to induction of jasmonic acid signaling. In addition, we propose that the cell wall may play an important role in restriction of Se movement to the cytoplasm. Also, we hypothesize that Se accumulates in cells by sequestration of selenate in the vacuole.

Accumulation of Selenium in Candida utilis Growing in Media of Increasing Concentration of this Element

Selenium is considered an essential component of all living organisms. Studies on the enrichment of yeast cells with selenium, using the ability of cell biomass to bind this element, are being reported more and more. Yeast cultures were cultivated in YPD medium enriched with Na2SeO3 salts for 72 h at 28 °C on a shaker utilizing reciprocating motion. Selenium in cell biomass was determined with the use of ICP–MS. It was observed that the addition of selenium to the experimental medium (in the range of 4–100 mg/L) increased the content of this element in the yeast cell biomass. During the extension of cultivation time, the number of yeast cells and biomass yield exhibited a decreasing trend. Based on the obtained results, it was concluded that yeast cells exhibited the ability to accumulate selenium in both logarithmic and stationary growth phases. The dose of 20 and 30 mg/L of selenium in the culture medium meets the expectations in terms of both the content of selenium bound to yeast cells (1944 ± 110.8 μg/g dry weight) under 48-h cultivation. The obtained results confirmed that the Candida utilis ATCC 9950 strain exhibits the ability to bind selenium, which means that the biomass of these yeasts may be used as a natural source of selenium in the diet of humans and animals.

Acclimation of copper absorption ability of Candida utilis

The use of inorganic copper in feed is hazardous. As probiotics of animals, Candida utilis can absorb copper ions and transform them to organic copper. This study aimed to domesticate the ability of C. utilis (CICC 32211) to absorb and transform copper ions. So, C. utilis (CICC 32211) was cultured in media with different concentrations of copper ions for 24, 48 and 72 h to identify the optimum copper ion concentration. C. utilis (CICC 32211) strains were domesticated for three generations, then the absorption and distribution of copper ions in the yeast cells were studied. We found that the optimum concentration of copper ions was 110 µg/mL. After 48 h, the number of yeast cells was low, but copper ion absorption efficiency was maximized (43.83%). Most of the enriched copper ions were distributed in the yeast cell wall (up to 30.58% when grown in the medium with 110 µg/mL copper ions), while the intracellular copper ion content was low (2.095%). High concentrations of copper ions affected the morphological structure, element content and distribution of yeast cells.

Transcriptome analysis reveals the mechanism underlying improved glutathione biosynthesis and secretion in Candida utilis during selenium enrichment

The effect of sodium selenite on batch culture of Candida utilis CCTCC M 209298 was investigated. Cell growth was inhibited while glutathione biosynthesis and secretion were improved during selenium enrichment. To reveal the mechanism underlying the decrease in biomass and the increase in glutathione, both metabolic flux analysis of key intermediates involved in glutathione metabolic pathway and transcriptome analysis of C. utilis by RNA-seq were carried out for selenized cells and the control without selenium enrichment. Results indicated that sodium selenite decreased carbon fluxes towards biomass but increased fluxes towards amino acids for the biosynthesis of glutathione and related amino acids. Selenium enrichment down-regulated a large number of genes involved in cell components and the cell cycle, resulting in decreased biomass as well as increased cell permeability. Moreover, several genes associated with transportation, binding, and mitochondrial and ribosomal functions for energy metabolism and protein synthesis were up-regulated in the presence of sodium selenite. All of these results disclosed the physiological response of C. utilis to sodium selenite.

Effects of selenium feed supplements on functional properties of eggs

The aim of the present study was to assess the effects of selenium feed supplements on the functional properties of eggs. The hens in experimental groups were fed diets supplemented with 0.2 mg/kg selenium from sodium selenite (Group 1), selenium-enriched yeast (Group 2), synthetic L-selenomethionine (Group 3), or hydroxy analog of selenomethionine (Group 4). The Control Group (Group C) was fed with basal feed without supplementation. The highest values of albumen gel firmness were shown in Group C eggs; differences with all experimental groups were significant (p < 0.001 to p = 0.009). It was ascertained that albumen gel firmness correlated with albumen pH (r_s = 0.490; p < 0.001), which was highest in eggs from non-supplemented hens. Group 1 eggs and Group C eggs showed lower albumen foaming capacity (p < 0.001) compared to eggs from other groups. Both albumen foaming capacity and albumen foam stability were higher in Group 2 eggs than in Group C eggs (p < 0.001). The highest yolk foaming capacity was found in Group 2 eggs (p < 0.001). Sponge cakes baked with Group C eggs had a smaller volume than those baked with eggs from Group 2 (p = 0.005), Group 3 (p = 0.004) and Group 4 (p = 0.024). The results of the study confirmed that selenium added to the laying hen feed significantly affected the monitored functional properties of both albumen and yolk. The most distinctive effect of selenium was shown in eggs from the group supplemented with selenium-enriched yeast, for which the results of albumen foam capacity and stability and yolk foaming capacity were the best.

Selenium-Yeast Alleviated Inflammatory Damage Caused by Lead via Inhibiting Ras/ERK Pathway and Inflammatory Factors in Chicken Skeletal Muscles

The aim of this study was to investigate the ameliorative effects of selenium-enriched yeast (Se-yeast) on the inflammatory damage induced by lead (Pb) in chicken skeletal muscles. A total of 108 1-day-old broiler chickens were randomly allocated into four groups (n = 27/group): the control group (C group), the Se-yeast-supplemented group (Se group), the lead-treated group (Pb group), and finally the Se- and Pb-combined group (Pb/Se group). The C group was fed with a basic diet comprising 0.049 mg/kg Se and 0.1 mg/kg Pb while the Se group was fed a Se-yeast diet containing 0.30 mg/kg Se and 0.1 mg/kg Pb. Similarly, the Pb group was fed a Pb acetate diet containing 0.049 mg/kg Se and 350 mg/kg Pb while the Pb/Se group was fed with a Se-yeast diet containing 0.30 mg/kg Se and 350 mg/kg Pb. On days 7, 21, and 35 after commencing the experiment, nine chicks belonging to each group were euthanized and the samples were analyzed by employing the techniques of inductively coupled plasma mass spectrometry and real-time quantitative PCR, along with Western blotting. The results indicated that excess Pb increased the nitric oxide concentration, enhanced the activity of inducible nitric oxide synthase (iNOS), and the mRNA levels of interleukin 1β (IL-1β), interleukin 4 (IL-4), interleukin 10 (IL-10), and interferon gamma (IFN-γ) in a time-dependent manner. Further, it was found that Se reduced damage caused by Pb by decreasing the expression of inflammatory factors in chicken skeletal muscles. Taken together, the results from this study provide the theoretical basis for an alleviate effect of Se on Pb-induced inflammatory damage in chicken skeletal muscles, mediated by inhibiting the Ras/extracellular signal-regulated kinase (ERK) pathway and the inflammatory factors.

Improvement of selenium enrichment in Rhodotorula glutinis X-20 through combining process optimization and selenium transport

Selenium-enriched yeast can transform toxic inorganic selenium into absorbable organic selenium, which is of great significance for human health and pharmaceutical industry. A yeast Rhodotorula glutinis X-20 we obtained before has good selenium-enriched ability, but its selenium content is still low for industrial application. In this study, strategies of process optimization and transport regulation of selenium were thus employed to further improve the cell growth and selenium enrichment. Through engineering phosphate transporters from Saccharomyces cerevisiae into R. glutinis X-20, the selenium content was increased by 21.1%. Through using mixed carbon culture (20 g L⁻¹, glycerol: glucose 3:7), both biomass and selenium content were finally increased to 5.3 g L⁻¹ and 5349.6 µg g⁻¹ (cell dry weight, DWC), which were 1.14 folds and 6.77 folds compared to their original values, respectively. Our results indicate that high selenium-enrichment ability and biomass production can be achieved through combining process optimization and regulation of selenium transport.

Physicochemical properties, antifungal activity and cytotoxicity of selenium sulfide nanoparticles green synthesized by Saccharomyces cerevisiae

Selenium sulfide is a well-known bioactive chemical whose biosynthesis as a nanoparticle (NP) is a controversial issue. In the present study, we employed Saccharomyces cerevisiae to generate a novel synthetic process of selenium sulfide NPs. The addition of selenium/sulfur precursors to S. cerevisiae culture produced NPs, which we isolated and characterized the physicochemical properties, toxicity, and antifungal activity. Transmission electron microscopy indicated the presence of the NPs inside the cells. Selenium sulfide NPs were successfully synthesized with average size of 6.0 and 153 nm with scanning electron micrographs and 360 and 289 nm in Zeta sizer using different precursors. The presence of sulfur/selenium in the particles was confirmed by energy-dispersive X-ray spectroscopy and elemental mapping. Fourier-transform infrared spectroscopy supported the production of selenium sulfide NPs. X-ray diffractograms showed the presence of characteristic peaks of selenium sulfide NPs which were further confirmed by mass spectrometry. The obtained NPs strongly inhibited the growth of pathogenic fungi that belonged to the genera Aspergillus, Candida, Alternaria and the dermatophytes, while no cytotoxicity was observed in MTT assay. In conclusion, efficient green synthesis of selenium sulfide NPs with appropriate physicochemical properties is possible in bio-systems like S. cerevisiae.

Selenium⁻Fascinating Microelement, Properties and Sources in Food

Selenium is a micronutrient that is essential for the proper functioning of all organisms. Studies on the functions of selenium are rapidly developing. This element is a cofactor of many enzymes, for example, glutathione peroxidase or thioredoxin reductase. Insufficient supplementation of this element results in the increased risk of developing many chronic degenerative diseases. Selenium is important for the protection against oxidative stress, demonstrating the highest activity as a free radical scavenger and anti-cancer agent. In food, it is present in organic forms, as exemplified by selenomethionine and selenocysteine. In dietary supplementation, the inorganic forms of selenium (selenite and selenate) are used. Organic compounds are more easily absorbed by human organisms in comparison with inorganic compounds. Currently, selenium is considered an essential trace element of fundamental importance for human health. Extreme selenium deficiencies are widespread among people all over the world. Therefore, it is essential to supplement the deficiency of this micronutrient with selenium-enriched food or yeast cell biomass in the diet.

Effect of selenium on growth and antioxidative system of yeast cells

Selenium exhibits health-promoting properties in humans and animals. Therefore, the development of selenium-enriched dietary supplements has been growing worldwide. However, it may also exhibit toxicity at higher concentrations, causing increased oxidative stress. Different species of yeasts may exhibit different tolerances toward selenium. Therefore, in this study, we aimed to determine the effect of selenium on growth and on the antioxidative system in Candida utilis ATCC 9950 and Saccharomyces cerevisiae ATCC MYA-2200 yeast cells. The results of this study have demonstrated that high doses of selenium causes oxidative stress in yeasts, thereby increasing the process of lipid peroxidation. In addition, we obtained an increased level of GSSG from aqueous solutions of yeast biomass grown with selenium supplementation (40-60 mg/L). Increased levels of selenium in aqueous solutions resulted in an increase in the activity of antioxidant enzymes, including glutathione peroxidase and glutathione reductase. These results should encourage future research on the possibility of a thorough understanding of antioxidant system functioning in yeast cells.

Crustin-capped selenium nanowires against microbial pathogens and Japanese encephalitis mosquito vectors - Insights on their toxicity and internalization

Herein, we reported a method to synthesize selenium nanowires (Cr-SeNWs) relying to purified cysteine-rich antimicrobial peptide crustin in presence of ascorbic acid. Cr-SeNWs were characterized by UV-vis, XRD, FTIR and Raman spectroscopy, as well as SEM, HR-TEM and EDAX. The UV-vis spectroscopy peak was noted at 350 nm. XRD showed the crystalline nature of Cr-SeNWs through diffraction peaks observed 2θ at 12° and 28° corresponding to (020), and (241) lattice planes, respectively. HR-TEM results shed light on the size of Cr-SeNWs, ranging from 17 to 47 nm. Raman spectroscopy and EDAX analysis of Cr-SeNWs showed presence of 57% selenium element. Furthermore, Cr-SeNWs showed higher antimicrobial activity on Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis) over Gram-negative ones (Pseudomonas aeruginosa, Escherichia coli). The zone of inhibition was larger on S. aureus (50 μg/ml = 4.0 mm, 75 μg/ml = 7.2 mm) and E. faecalis (50 μg/ml = 3.1 mm, 75 μg/ml = 5.1 mm), over P. aeruginosa (50 μg/ml = 2.1 mm, 75 μg/ml = 4.8 mm), E. coli (50 μg/ml = 1.3 mm, 75 μg/ml = 4.3 mm) bacteria. The antibiofilm activity of Cr-SeNWs was also investigated and biofilm reduction was observed at 75 μg/ml. In addition, Cr-SeNWs were highly effective as larvicides against Zika virus and Japanese encephalitis mosquito vectors, i.e., Culex quinquefasciatus and Culex tritaeniorhynchus, with LC₅₀ values of 4.15 and 4.85 mg/l, respectively. The nanowire toxicity and internalization was investigated through confocal laser scanning microscopy and histological studies. To investigate the potential of Cr-SeNWs for real-world applications, we also evaluated Cr-SeNWs in hemolytic assays, showing no cytotoxicity till 5 mg/ml. Besides, higher antioxidant activity at the concentration at 100 μg/ml was noted, if compared with purified crustin. The strong antioxidant potential of this nanomaterial can be helpful to boost the shelf-life potential of Cr-SeNWs-based pesticides and antimicrobials.

Effect of Selenium on Lipid and Amino Acid Metabolism in Yeast Cells

This article discusses the effect of selenium in aqueous solutions on aspects of lipid and amino acid metabolism in the cell biomass of Saccharomyces cerevisiae MYA-2200 and Candida utilis ATCC 9950 yeasts. The yeast biomass was obtained by using waste products (potato wastewater and glycerol). Selenium, at a dose of 20 mg/L of aqueous solution, affected the differentiation of cellular morphology. Yeast enriched with selenium was characterized by a large functional diversity in terms of protein and amino acid content. The protein content in the biomass of S. cerevisiae enriched with selenium (42.6%) decreased slightly as compared to that in the control sample without additional selenium supplementation (48.4%). Moreover, yeasts of both strains enriched with selenium contained a large amount of glutamic acid, aspartic acid, lysine, and leucine. Analysis of fatty acid profiles in S. cerevisiae yeast supplemented with selenium showed an increase in the unsaturated fatty acid content (e.g., C18:1). The presence of margaric acid (C17:0) and hexadecanoic acid (C17:1) was found in the C. utilis biomass enriched with selenium, in contrast to that of S. cerevisiae. These results indicate that selenium may induce lipid peroxidation, which consequently affects the loss of integrity of the cytoplasmic membrane. Yeast enriched with selenium with optimal amino acid and lipid composition can be used to prepare a novel formula of dietary supplements, which can be applied directly to various diets for both humans and animals.

Sourdough Fermentation Favorably Influences Selenium Biotransformation and the Biological Effects of Flatbread

Although selenium is of great importance for the human body, in several world regions the intake of this essential trace element does not meet the dietary reference values. To achieve optimal intake, fortification of bread by using selenium-enriched flour has been put forward. Less is known on the potential effect of sourdough fermentation, which might be worth exploring as the biological effects of selenium strongly depend on its chemical form and sourdough fermentation is known to cause transformations of nutrients and phytochemicals, including the conversion of inorganic selenium into organic selenocompounds. Here we investigated the bio transformation of selenium by sourdough fermentation in a typical Italian flatbread (piadina) made with standard (control) or selenium-enriched flour. The different piadina were submitted to in vitro digestion, and the biological activity of the resulting hydrolysates was tested by means of cultured human liver cells exposed to an exogenous oxidative stress. The use of selenium-enriched flour and sourdough fermentation increased the total content of bioaccessible selenium in organic form, compared to conventional fermentation, and led to protective effects counteracting oxidative damage in cultured cells. The present study suggests that selenium-rich, sourdough-fermented bakery products show promise for improving human selenium nutrition whenever necessary.

Selenium Nanoparticle Synthesized by Proteus mirabilis YC801: An Efficacious Pathway for Selenite Biotransformation and Detoxification

Selenite is extremely biotoxic, and as a result of this, exploitation of microorganisms able to reduce selenite to non-toxic elemental selenium (Se⁰) has attracted great interest. In this study, a bacterial strain exhibiting extreme tolerance to selenite (up to 100 mM) was isolated from the gut of adult Monochamus alternatus and identified as Proteus mirabilis YC801. This strain demonstrated efficient transformation of selenite into red selenium nanoparticles (SeNPs) by reducing nearly 100% of 1.0 and 5.0 mM selenite within 42 and 48 h, respectively. Electron microscopy and energy dispersive X-ray analysis demonstrated that the SeNPs were spherical and primarily localized extracellularly, with an average hydrodynamic diameter of 178.3 ± 11.5 nm. In vitro selenite reduction activity assays and real-time PCR indicated that thioredoxin reductase and similar proteins present in the cytoplasm were likely to be involved in selenite reduction, and that NADPH or NADH served as electron donors. Finally, Fourier-transform infrared spectral analysis confirmed the presence of protein and lipid residues on the surfaces of SeNPs. This is the first report on the capability of P. mirabilis to reduce selenite to SeNPs. P. mirabilis YC801 might provide an eco-friendly approach to bioremediate selenium-contaminated soil/water, as well as a bacterial catalyst for the biogenesis of SeNPs.

Speciation Analysis of Selenium in Candida utilis Yeast Cells Using HPLC-ICP-MS and UHPLC-ESI-Orbitrap MS Techniques

Selenium plays a key role in the proper metabolism of living organisms. The search for new selenium compounds opens up new possibilities for understanding selenometabolome in yeast cells. This study was aimed at the identification of compounds containing selenium in the feed yeasts Candida utilis ATCC 9950. Yeast biomass was kept in aqueous solutions enriched with inorganic selenium (20 mg·L−1) for 24 h. Speciation analysis of the element was performed using the HPLC-ICP-MS and UHPLC-ESI-Orbitrap MS techniques. The obtained selenium value in the yeast was 629 μg·g−1, while the selenomethionine value was 31.57 μg·g−1. The UHPLC-ESI-Orbitrap MS analysis conducted allowed for the identification of six selenium compounds: dehydro-selenomethionine-oxide, selenomethionine, selenomethionine-NH3, a Se-S conjugate of selenoglutathione-cysteine, methylthioselenoglutathione, and 2,3-DHP-selenocysteine-cysteine. In order to explain the structure of selenium compounds, the selected ions were subjected to fragmentation. The selenium compounds obtained with a low mass play a significant role in the metabolism of the compound. However, the bioavailability of such components and their properties have not been fully understood. The number of signals indicating the presence of selenium compounds obtained using the UHPLC-ESI-Orbitrap MS method was characterized by higher sensitivity than when using the HPLC-ICP-MS method. The obtained results will expand upon knowledge about the biotransformation of selenium in eukaryotic yeast cells. Future research should focus on understanding the entire selenium metabolism in cells and on the search for new transformation pathways for this element. This opens up new possibilities for obtaining functional food, rich in easily absorbable selenium sources, and constituting an alternative to dietary supplements based on this compound found primarily in inorganic form.

Selenite Reduction and the Biogenesis of Selenium Nanoparticles by Alcaligenesfaecalis Se03 Isolated from the Gut of Monochamus alternatus (Coleoptera: Cerambycidae)

In this study, a bacterial strain exhibiting high selenite (Na₂SeO₃) tolerance and reduction capacity was isolated from the gut of Monochamus alternatus larvae and identified as Alcaligenes faecalis Se03. The isolate exhibited extreme tolerance to selenite (up to 120 mM) when grown aerobically. In the liquid culture medium, it was capable of reducing nearly 100% of 1.0 and 5.0 mM Na₂SeO₃ within 24 and 42 h, respectively, leading to the formation of selenium nanoparticles (SeNPs). Electron microscopy and energy dispersive X-ray analysis demonstrated that A. faecalis Se03 produced spherical electron-dense SeNPs with an average hydrodynamic diameter of 273.8 ± 16.9 nm, localized mainly in the extracellular space. In vitro selenite reduction activity and real-time PCR indicated that proteins such as sulfite reductase and thioredoxin reductase present in the cytoplasm were likely to be involved in selenite reduction and the SeNPs synthesis process in the presence of NADPH or NADH as electron donors. Finally, using Fourier-transform infrared spectrometry, protein and lipid residues were detected on the surface of the biogenic SeNPs. Based on these observations, A. faecalis Se03 has the potential to be an eco-friendly candidate for the bioremediation of selenium-contaminated soil/water and a bacterial catalyst for the biogenesis of SeNPs.

Equilibrium modeling of selenium binding from aqueous solutions by Candida utilis ATCC 9950 yeasts

The study investigated the effectiveness of selenium binding from its salt solution by Candida utilis ATCC 9950 yeast biomass cultured on a medium prepared from the agro-food industry wastes, containing an available source of carbon and nitrogen. Selenium binding by C. utilis yeast strain after 48 h of culturing at 28 °C from aqueous solutions with the addition of 30 mg Se/L reached a value of 2.28 mg Se/g of yeast biomass. The kinetics of selenium binding by the yeasts showed a better fit for the pseudo-second-order kinetic model compared to the pseudo-first-order one. Accumulation stability data were analyzed using the Freundlich and Langmuir isotherm models. The presence of competing anions such as SO 4 2 - , and HPO 4 2 - at a concentration of 0.5 mM resulted in about 35% reduction of selenium binding by the examined C. utilis strain. FTIR analysis showed that sulfur compounds were involved in selenium biosorption by the yeast. Compounds containing ammonium groups appeared to be very important for selenium binding. The results of the study demonstrated that the yeast can be used to effectively bind selenium from aqueous solution. At the same time, it gives the opportunity to obtain a biomass rich in this deficient element, which can also be used in dietary supplement production.

Directed Evolution of Saccharomyces cerevisiae for Increased Selenium Accumulation

Selenium-enriched yeast (selenium yeast) are one of the most popular sources of selenium supplementation used in the agriculture and human nutritional supplements industries. To enhance the production efficiency of selenium yeast, we sought to develop a method to identify, and ultimately select for, strains of yeast with enhanced selenium accumulation capabilities. Selenite resistance of four genetically diverse strains of Saccharomyces cerevisiae was assayed in various conditions, including varying carbon sources, nitrogen sources, and phosphate amounts, and they were correlated with selenium accumulation in a commercially relevant selenium-containing growth medium. Glycerol- and selenite-containing media was used to select for six yeast isolates with enhanced selenite resistance. One isolate was found to accumulate 10-fold greater selenium (0.13 to 1.4 mg Se g⁻¹ yeast) than its parental strain. Glycerol- and selenium-containing medium can be used to select for strains of yeast with enhanced selenium accumulation capability. The methods identified can lead to isolation of industrial yeast strains with enhanced selenium accumulation capabilities that can result in greater cost efficiency of selenium yeast production. Additionally, the selection method does not involve the construction of transgenic yeast, and thus produces yeasts suitable for use in human food and nutrient supplements.

Synergistic antifungal effect of chitosan-stabilized selenium nanoparticles synthesized by pulsed laser ablation in liquids against Candida albicans biofilms

BACKGROUND

Candida albicans is a major opportunistic fungal pathogen. One of the most important virulence factors that contribute to the pathogenesis of candidiasis is its ability to form biofilms. A key characteristic of Candida biofilms is their resistance to antifungal agents. Due to significant morbidity and mortality rates related to biofilm-associated drug resistance, there is an urgency to develop novel nanotechnology-based approaches preventing biofilm-related infections.

METHODS

In this study, we report, for the first time, the synthesis of selenium nanoparticles by irradiating selenium pellets by nanosecond pulsed laser ablation in liquid chitosan as a capping agent. Synergy of the fungicidal effect of selenium nanoparticles and chitosan was quantified by the combination index theorem of Chou-Talalay.

RESULTS

This drug combination resulted in a potent fungicidal effect against a preformed C. albicans biofilm in a dose-response manner. By advanced electron microscopy techniques, we documented the adhesive and permeabilizing properties of chitosan, therefore allowing selenium nanoparticles to enter as the cell wall of the yeast became disrupted and distorted. Most importantly, we demonstrated a potent quantitative synergistic effect when compounds such as selenium and chitosan are combined.

CONCLUSION

These chitosan-stabilized selenium nanoparticles could be used for ex vivo applications such as sterilizers for surfaces and biomedical devices.

Selenium Deficiency Augments the Levels of Inflammatory Factors and Heat Shock Proteins via the Redox Regulatory Pathway in the Skeletal Muscles of Mice

Dietary selenium (Se) deficiency is known to cause myodynia syndrome and Se influences immune responses by changing the expression of inflammatory cytokines and heat shock proteins (Hsps), but the details are not completely elucidated. In the present study, 72 1-day-old mice were divided into two groups; the first group was fed a Se-sufficient diet, while the second group was fed a Se-deficient diet. Skeletal muscles and blood samples were taken from all mice after 42 days of treatment. The activities of glutathione peroxidase (GPX) and glutathione (GSH), mRNA and protein expression levels of inflammatory cytokines (including TNF-α, inducible NO synthase, cyclooxygenase-2, and prostaglandin E synthases), protein expression levels of NF-κB, and the mRNA expression levels of Hsps in the skeletal muscles of mice were examined. The results showed that GPX and GSH activities were decreased, while the mRNA and protein expression levels of inflammatory cytokines and the mRNA levels of Hsps were increased by Se deficiency in mouse skeletal muscles. In the present study, the protective role of Se in oxidative stress, inflammatory cytokines, and Hsps in the skeletal muscles of mice was summarized.

Expanding beyond canonical metabolism: Interfacing alternative elements, synthetic biology, and metabolic engineering

Metabolic engineering offers an exquisite capacity to produce new molecules in a renewable manner. However, most industrial applications have focused on only a small subset of elements from the periodic table, centered around carbon biochemistry. This review aims to illustrate the expanse of chemical elements that can currently (and potentially) be integrated into useful products using cellular systems. Specifically, we describe recent advances in expanding the cellular scope to include the halogens, selenium and the metalloids, and a variety of metal incorporations. These examples range from small molecules, heteroatom-linked uncommon elements, and natural products to biomining and nanotechnology applications. Collectively, this review covers the promise of an expanded range of elemental incorporations and the future impacts it may have on biotechnology.

Recent advances in the mechanism of selenoamino acids toxicity in eukaryotic cells

Selenium is an essential trace element due to its incorporation into selenoproteins with important biological functions. However, at high doses it is toxic. Selenium toxicity is generally attributed to the induction of oxidative stress. However, it has become apparent that the mode of action of seleno-compounds varies, depending on its chemical form and speciation. Recent studies in various eukaryotic systems, in particular the model organism Saccharomyces cerevisiae, provide new insights on the cytotoxic mechanisms of selenomethionine and selenocysteine. This review first summarizes current knowledge on reactive oxygen species (ROS)-induced genotoxicity of inorganic selenium species. Then, we discuss recent advances on our understanding of the molecular mechanisms of selenocysteine and selenomethionine cytotoxicity. We present evidences indicating that both oxidative stress and ROS-independent mechanisms contribute to selenoamino acids cytotoxicity. These latter mechanisms include disruption of protein homeostasis by selenocysteine misincorporation in proteins and/or reaction of selenols with protein thiols.