Distribution and speciation of selenium in soybean proteins and its effect on protein structure and functionality

Bioaccumulation and biotransformation of selenium nanoparticles in soybean and natto, and the bioaccessibility of multi-elements and amino acids

Soybean is a food crop with strong selenium (Se) enrichment ability. Selenium nanoparticles (SeNPs) are a low-toxic Se source. To develop strategies in SeNPs biofortification of soybean and natto, the effects of Se enrichment and natto fermentation on selenoamino acids, mineral elements, free amino acids, γ-polyglutamic acid, nattokinase, and bioaccessibility were investigated. Soybean grains were able to convert SeNPs into selenomethionine (SeMet). Selenium enrichment and natto fermentation influenced the enrichment and distribution of multi-elements in soybean, as well as the composition of free and bound amino acids. Selenium enrichment had no significant effect on the bioaccessibility of amino acids. After natto fermentation, the bioaccessibility of SeMet, Fe, Mn, Cu, and Zn in the gastrointestinal tract increased significantly by 10.1-18.9 %. These findings indicate that SeNPs can enhance the Se content of soybean grains, and natto fermentation can further improve the nutritional quality of Se-enriched soybean.

Effects of selenium biofortification on Pleurotus eryngii protein structure and digestive properties and its mitigation of lead toxicity: An in vitro and in vivo study

The development of safe and efficient dietary selenium sources to promote lead excretion is of great importance for public health. In this research, proteins from original Pleurotus eryngii (PEP) and Se-enriched P. eryngii (SePEP, Se content: 360.64 ± 3.11 mg/kg) were extracted and purified respectively for the further comparison of structural and digestive characteristics. Caco-2 monolayer membrane, in vitro simulated fermentation and acute lead exposure mice model were constructed to evaluate the effects of PEP and SePEP on lead excretion. The results indicated that Se biofortification significantly altered the amino acid composition and reduced the total sulfhydryl content of proteins (p < 0.05). SePEP could better alleviate lead-induced intestinal barrier damage and inhibit the absorption and accumulation of lead in both cell and mice models. Furthermore, SePEP promoted fecal adsorption and excretion of lead via regulating gut microbiota composition. SePEP can be considered a potentially functional Se source to promote lead excretion.

Effect of exogenous selenium on physicochemical, structural, functional, thermal, and gel rheological properties of mung bean (Vigna radiate L.) protein

Selenium (Se) biofortification during the growth process of mung bean is an effective method to improve the Se content and quality. However, the effect of Se biofortification on the physicochemical properties of mung bean protein is unclear. The objective of this study was to clarify the changes in the composition, Se forms, particle structure, functional properties, thermal stability, and gel properties of mung bean protein at four Se application levels. The results showed that the Se content of mung bean protein increased in a dose-dependent manner, with 7.96-fold (P1) and 8.52-fold (P2) enhancement at the highest concentration. Exogenous Se application promotes the conversion of inorganic Se to organic Se. Among them, selenomethionine (SeMet) and methyl selenocysteine (MeSeCys) replaced Met and Cys through the S metabolic pathway and became the dominant organic Se forms in Se-enriched mung bean protein, accounting for more than 80 % of the total Se content. Exogenous Se at 30 g/hm2 significantly up-regulated protein content and promoted the synthesis of sulfur-containing protein components and hydrophobic amino acids in the presence of increased levels of SeMet and MeSeCys. Meanwhile, Cys and Met substitution altered the sulfhydryl groups (SH), β-sheets, and β-turns of protein. The particle size and microstructural characteristics depend on the protein itself and were not affected by exogenous Se. The Se-induced increase in the content of hydrophobic amino acids and β-sheets synergistically increases the thermal stability of the protein. Moderate Se application altered the functional properties of mung bean protein, which was mainly reflected in the significant increase in oil holding capacity (OHC) and foaming capacity (FC). In addition, the increase in SH and β-sheets induced by exogenous Se could alter the protein intermolecular network, contributing to the increase in storage modulus (G') and loss modulus (G″), which resulted in the formation of more highly elastic gels. This study further promotes the application of mung bean protein in the field of food processing and provides a theoretical basis for the extensive development of Se-enriched mung bean protein.

Liposomes as selenium nanocarriers for foliar application to wheat plants: A biofortification strategy

In the present work, liposomes have been used as nanocarriers in the biofortification of wheat plants with selenium (Se) through foliar application. Liposomal formulations were prepared using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and Phospholipon®90H (P90H) (average size <100 nm), loaded with different concentrations of inorganic Se (selenite and selenate) and applied twice to the plants in the stage of vegetative growth. Liposomes enhanced Se uptake by wheat plants compared to direct application. The highest Se enrichment was achieved using the phospholipid DPPC and a concentration of 1000 μmol·L-1 of Se without affecting the biomass, chlorophylls, carotenoids, and the concentration of mineral nutrients of the plants. The chemical speciation of Se in the plants was further investigated by X-ray absorption spectroscopy (XAS). The results from XAS spectra revealed that most of the inorganic Se was transformed to organic Se and that the use of liposomes influenced the proportion of C-Se-C over C-Se-Se-C species.

Characterization of Selenium Speciation in Se-Enriched Crops: Crop Selection Approach

Accurately quantifying selenium (Se) speciation and transformation in Se-enriched crops is highly significant for human health. The investigation of Se species in Se-enriched crops involves assessing the enrichment of both organic and inorganic Se species, considering their plant families and edible parts. The staple crops of rice, corn, and wheat showed no or less inorganic Se with the increase of total Se; however, potatoes expressed a proportion of selenate [Se(VI)]. In addition, the organic Se proportions in Se-enriched crops of Cruciferous, Brassicaceae, and Umbelliferae plant families were relatively lower than the proportion of inorganic Se. Concurrently, the edible parts of the Se-enriched gramineous or cereal crops enriched with organic Se and crops with fruit, stem, leaf, and root as edible parts contain the maximum percentage of organic Se with a certain proportion of inorganic Se. This study contributes to a sparse body of literature by meticulously discerning appropriate Se-enriched crop selection through a comprehensive evaluation of Se speciation and its organic and inorganic accumulation potential.

Selenoproteins in Health

Selenium (Se) is a naturally occurring essential micronutrient that is required for human health. The existing form of Se includes inorganic and organic. In contrast to the inorganic Se, which has low bioavailability and high cytotoxicity, organic Se exhibits higher bioavailability, lower toxicity, and has a more diverse composition and structure. This review presents the nutritional benefits of Se by listing and linking selenoprotein (SeP) functions to evidence of health benefits. The research status of SeP from foods in recent years is introduced systematically, particularly the sources, biochemical transformation and speciation, and the bioactivities. These aspects are elaborated with references for further research and utilization of organic Se compounds in the field of health.

Foliar Application of Selenium Associated with a Multi-Nutrient Fertilizer in Soybean: Yield, Grain Quality, and Critical Se Threshold

Selenium uptake and its content in soybean grains are affected by Se application methods. This study evaluated the impact of Se foliar application combined with a multi-nutrient fertilizer (MNF) on soybean, establishing a Se threshold to better understand the relationship between Se content in grains and yield of two genotypes (58I60 Lança and M5917). Two trials were conducted in a 4 × 2 factorial design: four Se rates (0, 10, 40, 80 g Se ha-1) and two methods of foliar Se application (Se combined or not with MNF). Foliar fertilizers were applied twice, at phenological stages of beginning of pod development and grain filling. Grain yield increased with the application of MNF, yet Se rates increased Se contents linearly up to 80 g Se ha-1, regardless of the use of MNF. Lança and M5917 genotypes had grain Se critical thresholds of 1.0 and 3.0 mg kg-1, respectively. The application of Se favored higher contents of K, P, and S in grains of genotype Lança and higher contents of Mn and Fe in grains of genotype M5917. Our findings highlight the importance of addressing different Se fertilization strategies as well as genotypic variations when assessing the effects of Se on soybean yield and grain quality.

Illumina RNA and SMRT Sequencing Reveals the Mechanism of Uptake and Transformation of Selenium Nanoparticles in Soybean Seedlings

Selenium (Se) is an essential element for mammals, and its deficiency in the diet is a global problem. Agronomic biofortification through exogenous Se provides a valuable strategy to enhance human Se intake. Selenium nanoparticles (SeNPs) have been regarded to be higher bioavailability and less toxicity in comparison with selenite and selenate. Still, little has been known about the mechanism of their metabolism in plants. Soybean (Glycine max L.) can enrich Se, providing an ideal carrier for Se biofortification. In this study, soybean sprouts were treated with SeNPs, and a combination of next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing was applied to clarify the underlying molecular mechanism of SeNPs metabolism. A total of 74,662 nonredundant transcripts were obtained, and 2109 transcription factors, 9687 alternative splice events, and 3309 long non-coding RNAs (lncRNAs) were predicted, respectively. KEGG enrichment analysis of the DEGs revealed that metabolic pathways, biosynthesis of secondary metabolites, and peroxisome were most enriched both in roots and leaves after exposure to SeNPs. A total of 117 transcripts were identified to be putatively involved in SeNPs transport and biotransformation in soybean. The top six hub genes and their closely coexpressed Se metabolism-related genes, such as adenylylsulfate reductase (APR3), methionine-tRNA ligase (SYM), and chloroplastic Nifs-like cysteine desulfurases (CNIF1), were screened by WGCNA and identified to play crucial roles in SeNPs accumulation and tolerance in soybean. Finally, a putative metabolism pathway of SeNPs in soybean was proposed. These findings have provided a theoretical foundation for future elucidation of the mechanism of SeNPs metabolism in plants.

Selenium biofortification of soybean genotypes in a tropical soil via Se-enriched phosphate fertilizers

Soybean is a major crop in Brazil and is usually grown in oxidic soils that need high rates of phosphate (P) fertilizers. Soybean is also very suitable for biofortification with Se, since its grains have high protein contents and are widely consumed worldwide (directly or indirectly). Few studies have addressed Se application under field conditions for soybean biofortification, especially in tropical soils. Here, we evaluated agronomic and physiological responses resulting from different strategies for biofortifying soybean grains with Se by applying this element via soil, using both conventional and enhanced-efficiency P fertilizers as Se carriers. The experiment was carried out at the Uva Farm, in Capão Bonito (São Paulo), Brazil. The experimental design was a randomized block split-plot design, with four fertilizer sources-conventional monoammonium phosphate (C-MAP), conventional monoammonium phosphate + Se (C-MAP + Se), enhanced-efficiency monoammonium phosphate (E-MAP), and enhanced-efficiency monoammonium phosphate + Se (E-MAP + Se), and four soybean genotypes (M5917, 58I60 LANÇA, TMG7061, and NA5909). The selenium rate applied via C-MAP + Se and E-MAP + Se was 80 g ha^-1. The application of the tested fertilizers was carried out at the sowing of the 2018/2019 cropping season, with their residual effect being also assessed in the 2019/2020 cropping season. Selenium application increased grain yield for the TMG7061 genotype. For all evaluated genotypes, Se content in grains increased in the 2018/2019 harvest with the application of Se via C-MAP + Se and E-MAP + Se. In general, the application of Se via C-MAP favored an increase in amino acid contents in grains and decreased lipid peroxidation. In summary, the application of Se-enriched P fertilizers via soil increased soybean grain yield, leading to better grain quality. No residual effects for biofortifying soybean grains were detected in a subsequent soybean cropping season.

Selenium Biofortification of Soybean Sprouts: Effects of Selenium Enrichment on Proteins, Protein Structure, and Functional Properties

Selenium (Se) biofortification during germination is an efficient method for producing Se-enriched soybean sprouts; however, few studies have investigated Se distribution in different germinated soybean proteins and its effects on protein fractions. Herein, we examined Se distribution and speciation in the dominant proteins 7S and 11S of raw soybean (RS), germinated soybean (GS), and germinated soybean with Se biofortification (GS-Se). The effects of germination and Se treatment on protein structure, functional properties, and antioxidant capacity were also determined. The Se concentration in GS-Se was 79.8-fold higher than that in GS. Selenomethionine and methylselenocysteine were the dominant Se species in GS-Se, accounting for 41.5–80.5 and 19.5–21.2% of the total Se with different concentrations of Se treatment, respectively. Se treatment had no significant effects on amino acids but decreased methionine in 11S. In addition, the α-helix contents decreased as the Se concentration increased; the other structures showed no significant changes. The Se treatment also had no significant effects on the water and oil-holding capacities in protein but increased the foaming capacity and emulsion activity index (EAI) of 7S, but only the EAI of 11S. The Se treatment also significantly increased the antioxidant capacity in 7S but not in 11S. This study indicates that the dominant proteins 7S and 11S have different Se enrichment abilities, and the protein structures, functional properties, and antioxidant capacity of GS can be altered by Se biofortification.

Influence of Selenium Biofortification of Soybeans on Speciation and Transformation during Seed Germination and Sprouts Quality

Selenium (Se) biofortification during seed germination is important not only to meet nutritional demands but also to prevent Se-deficiency-related diseases by producing Se-enriched foods. In this study, we evaluated effects of Se biofortification of soybeans on the Se concentration, speciation, and species transformation as well as nutrients and bioactive compounds in sprouts during germination. Soybean (Glycine max L.) seedlings were cultivated in the dark in an incubator with controlled temperature and water conditions and harvested at different time points after soaking in Se solutions (0, 5, 10, 20, 40, and 60 mg/L). Five Se species and main nutrients in the sprouts were determined. The total Se content increased by 87.3 times, and a large portion of inorganic Se was transformed into organic Se during 24 h of germination, with 89.3% of the total Se was bound to soybean protein. Methylselenocysteine (MeSeCys) and selenomethionine (SeMet) were the dominant Se species, MeSeCys decreased during the germination, but SeMet had opposite trend. Se biofortification increased contents of total polyphenol and isoflavonoid compounds and amino acids (both total and essential), especially in low-concentration Se treatment. In conclusion, Se-enriched soybean sprouts have promising potential for Se supplementation and as functional foods.

Selenomethionine-Dominated Selenium-Enriched Peanut Protein Ameliorates Alcohol-Induced Liver Disease in Mice by Suppressing Oxidative Stress

Numerous natural compounds are considered as potential therapeutic agents against alcohol-induced liver disease (ALD). Research shows that selenium (Se) has a variety of bioactivities, including liver protecting ability. The present study based on in vitro cell culture models and in vivo mouse models was aimed at examining the contribution of selenomethionine (SeMet)-dominated Se-enriched peanut protein (SePP) to liver protection. SeMet and especially SePP reversed cell viability and cell death, inhibited ethanol induced CYP2E1 activation, decreased reactive oxygen species level, and restored GSH level. Hence, SeMet-dominated SePP alleviates alcohol-induced AML-12 cytotoxicity by suppressing oxidative stress. The p38-dependent mechanism was found to be responsible for SePP-induced Nrf-2 activation. Furthermore, supplementation with SePP and SeMet regulated lipid metabolism and reduced oxidative stress, minimizing liver damage in mice. Selenomethionine-dominated SePP possesses potential therapeutic properties and can be used to treat ALD through the suppression of oxidative stress.