Benefit-risk assessment of dietary selenium and its associated metals intake in China (2017-2019): Is current selenium-rich agro-food safe enough?

Risk assessment and impact prediction of associated heavy metal pollution in selenium-rich farmland

Selenium (Se)-rich farmland is a valuable and nonrenewable resource for addressing the global challenge of Se deficiency. However, frequent warnings of heavy metal pollution have threatened the safety and legitimacy of Se-rich functional agriculture, eventually damaged public health security. Definitive and judgmental quantitative studies on this hazardous phenomenon are still missing. Relevant reviews published in the past have summarized textual descriptions of the problem, lacking the support of the necessary statistical analysis of the data. Based on the collected publications, the present study evaluated and analyzed the sources, risks and impacts of heavy metal pollution in Se-rich farmland. Concentrations of cadmium (Cd), arsenic, lead and zinc in Se-rich farmland were significantly higher than those in non-Se-rich farmland, especially Cd. Pollution source analyses indicated that Se enrichment and heavy metal pollution occurred simultaneously in farmland, related to Se-heavy metal homology in rocks. According to environmental risk assessment, both serious Cd pollution and the narrow Se concentration range of safety utilization limited the availability of Se-rich farmland. Pollution impact predictions showed that the pollution in Se-rich farmland would result in serious human health risks to consumers and economic losses of 4000 yuan/hm2 on production side. Tackling Cd pollution was anticipated to recover economic losses (81 %) while lowering the carcinogenic (60 %) and non-carcinogenic (10 %) health risks. Our study also provided recommendations to address heavy metal pollution in Se-rich farmland. The two criteria should be followed by pollution control strategies applied to Se-rich functional agriculture including (i) not affecting the original Se enrichment in plant and (ii) not being interfered by Se in soil-plant systems. This will provide valuable information for Se-rich functional agriculture and public health security.

Selenium-Mediated (-)-Epigallocatechin-3-Gallate Dynamics via Flavanone-3-Hydroxylase Regulation of Flavonoid Biosynthesis in Fu Tea (Camellia sinensis (L.) O. Kuntze)

Tea (Camellia sinensis (L.) O. Kuntze) is a highly selenium enrichment capacity plant; high selenium concentration contributes to the occurrence of oxidative stress and protein misfolding in tea plants, whereas flavonoids can chelate heavy metals to protect plants from oxidative stress caused by metal exposure. Nevertheless, the role of catechins in flavonoid synthesis and nutrient metabolism under selenium stress remains unidentified. Combining Word2vec and HNSW utilizing UHPLC-Q-Orbitrap HRMS-MS/MS to implement rapid matching annotation of the structural information on metabolites in Fu tea, we found that selenium-mediated changes in catechins in Fu tea were mainly associated with flavonoid biosynthesis pathways. The results demonstrated that selenium treatment increased benign selenol analogues (glutathioselenol) in tea and identified the novel selenopeptide PRSeMW (m/z 636.22571, Pro-Arg-SeMet-Trp) in selenium-enriched Fu tea samples to enhance the health benefits of tea. The selenium levels were negatively correlated with N5-ethyl-l-glutamine (11.63 to 4.26 mg kg-1) and (-)-epigallocatechin (13.26 to 11.19 mg kg-1), increasing the accumulation of tea polyphenols ((-)-catechin gallate, (-)-epigallocatechin 3-gallate, and (+)-gallocatechin), and decreasing the level of caffeine. These discoveries provide new insights into the mechanism of tea polyphenol-mediated transformation of selenium in Fu tea and theoretical support for the quality assessment of selenium-enriched tea.

Comprehensive physiology and proteomics analysis revealed the molecular toxicological mechanism of Se stress on indica and japonica rice

Selenium pollution can lead to a decrease in crop yield and quality. However, the toxicological mechanisms of high Se concentrations on crops remain unclear. This study aimed to elucidate the physiological and proteomic molecular responses to Se stress in Oryza sativa. The results showed that under selenium stress, enzymatic activities of catalase, peroxidase, and superoxide dismutase in indica rice decreased by 61%, 28%, and 68%, respectively. The contents of non-enzymatic antioxidant substances ascorbic acid, glutathione, cysteine, proline, anthocyanidin, and flavonoids were decreased by 13%, 39%, 46%, 32%, 20%, and 5%, respectively, which significantly inhibited the antioxidant stress process of plants. At the same time, the results of proteomics analysis showed that rice seedlings, under Se stress, are involved in photosynthesis, photosynthesis-antenna proteins, carbon fixation, porphyrin metabolism, glyoxylate, and dicarboxylate. The differentially expressed proteins in metabolism and glutathione metabolism pathways showed a downward trend. It significantly inhibited the anti-oxidative stress, photosynthesis, and energy cycling process in plant cells, destroyed the homeostasis balance of rice plants, and inhibited the growth and development of rice. This finding reveals the molecular toxicological mechanism of Se stress on rice seedlings and provides a possible way to improve Se-resistant rice seedlings.

Selenium Nanomaterials Enhance Sheath Blight Resistance and Nutritional Quality of Rice: Mechanisms of Action and Human Health Benefit

In the current work, the foliar application of selenium nanomaterials (Se0 NMs) suppressed sheath blight in rice (Oryza sativa). The beneficial effects were nanoscale specific and concentration dependent. Specifically, foliar amendment of 5 mg/L Se0 NMs decreased the disease severity by 68.8% in Rhizoctonia solani-infected rice; this level of control was 1.57- and 2.20-fold greater than that of the Se ions with equivalent Se mass and a commercially available pesticide (Thifluzamide). Mechanistically, (1) the controlled release ability of Se0 NMs enabled a wider safe concentration range and greater bioavailability to Se0 NMs, and (2) transcriptomic and metabolomic analyses demonstrated that Se0 NMs simultaneously promoted the salicylic acid- and jasmonic-acid-dependent acquired disease resistance pathways, antioxidative system, and flavonoid biosynthesis. Additionally, Se0 NMs improved rice yield by 31.1%, increased the nutritional quality by 6.4-7.2%, enhanced organic Se content by 44.8%, and decreased arsenic and cadmium contents by 38.7 and 42.1%, respectively, in grains as compared with infected controls. Human simulated gastrointestinal tract model results showed that the application of Se0 NMs enhanced the bioaccessibility of Se in grains by 22.0% and decreased the bioaccessibility of As and Cd in grains by 20.3 and 13.4%, respectively. These findings demonstrate that Se0 NMs can serve as an effective and sustainable strategy to increase food quality and security.

Protective effects and mechanism of chemical- and plant-based selenocystine against cadmium-induced liver damage

Although selenium (Se) and cadmium (Cd) often coexist naturally in the soil of China, the health risks to local residents consuming Se-Cd co-enriched foods are unknown. In the present study, we investigated the effects of chemical-based selenocystine (SeCys2) on cadmium chloride-induced human hepatocarcinoma (HepG2) cell injury and plant (Cardamine hupingshanensis)-derived SeCys2 against Cd-induced liver injury in mice. We found that chemical- and plant-based SeCys2 showed protective effects against Cd-induced HepG2 cell injury and liver damage in mice, respectively. Compared with Cd intervention group, co-treatment with chemical- or plant-based SeCys2 both alleviated liver toxicity and ferroptosis by decreasing ferrous iron, acyl-CoA synthetase long-chain (ACSL) family member 4, lysophosphatidylcholine acyltransferase 3, reactive oxygen species and lipid peroxide levels, and increasing ACSL3, peroxisome proliferator-activated receptor α, solute carrier family 7 member 11 (SLC7A11) and glutathione and glutathione peroxidase 4 (GPX4) levels. In conclusion, chemical- and plant-based SeCys2 alleviated Cd-induced hepatotoxicity and ferroptosis by regulating SLC7A11/GPX4 signaling and lipid peroxidation. Our findings indicate that potential Cd toxicity from consuming foods grown in Se- and Cd-rich soils should be re-evaluated. This study offers a new perspective for the development of SeCys2-enriched agricultural products.

Selenium-oxidizing Agrobacterium sp. T3F4 decreases arsenic uptake by Brassica rapa L. under a native polluted soil

Toxic arsenic (As) and trace element selenium (Se) are transformed by microorganisms but their complex interactions in soil-plant systems have not been fully understood. An As- and Se- oxidizing bacterium, Agrobacterium sp. T3F4, was applied to a native seleniferous As-polluted soil to investigate As/Se uptake by the vegetable Brassica rapa L. and As-Se interaction as mediated by strain T3F4. The Se content in the aboveground plants was significantly enhanced by 34.1%, but the As content was significantly decreased by 20.5% in the T3F4-inoculated pot culture compared to the control (P < 0.05). Similar result was shown in treatment with additional 5 mg/kg of Se(IV) in soil. In addition, the As contents in roots were significantly decreased by more than 35% under T3F4 or Se(IV) treatments (P<0.05). Analysis of As-Se-bacterium interaction in a soil simulation experiment showed that the bioavailability of Se significantly increased and As was immobilized with the addition of the T3F4 strain (P < 0.05). Furthermore, an As/Se co-exposure hydroponic experiment demonstrated that As uptake and accumulation in plants was reduced by increasing Se(IV) concentrations. The 50% growth inhibition concentration (IC50) values for As in plants were increased about one-fold and two-fold under co-exposure with 5 and 10 µmol/L Se(IV), respectively. In conclusion, strain T3F4 improves Se uptake but decreases As uptake by plants via oxidation of As and Se, resulting in decrease of soil As bioavailability and As/Se competitive absorption by plants. This provides a potential bioremediation strategy for Se biofortification and As immobilization in As-polluted soil.

Health risk assessment of heavy metals in saffron (Crocus sativus L.) cultivated in domestic wastewater and lake water irrigated soils

Irrigation of crops with domestic wastewater (DW) is a common practice in developing countries like India. However, domestic wastewater irrigation poses a risk of migration of toxic heavy metals to edible parts of crops, which requires serious measures to prevent their uptake. In this study, the effect of DW irrigation in comparison with Sarbal Lake water (SLW) and borewell water (BW) on soil characteristics and cultivated saffron (Crocus sativus L.) was investigated. For this purpose, samples of water, soil, and saffron (corm, petal, and stigma) were collected from the suburban area of Pampore, Srinagar district, Jammu and Kashmir, India. The results showed that DW irrigation had the maximum significant (p < 0.05) influence on the physico-chemical and nutrient characteristics of the soil, followed by SLW and BW irrigation, respectively. The growth and yield parameters of saffron were also significantly (p < 0.05) increased in the case of DW irrigation as compared to SLW and BW. The quality ranking of the cultivated saffron was found to be in accordance with the ISO standard (III: BW and II: DW and SLW). On the other hand, DW irrigation showed a significant increase in heavy metal contents (mg/kg) of saffron plant parts such as As (0.21-0.40), Cd (0.04-0.09), Cr (0.16-0.41), Cu (7.31-14. 75), Fe (142.38-303.15), Pb (0.18-0.31), Mn (15.26-22.81), Hg (0.18-0.25), Ni (0.74-1.18), Se (0.13-0.22), and Zn (3.44-4.59), followed by SLW and BW. However, the levels of heavy metals did not exceed the FAO/WHO safe limits. Bioaccumulation factor (BAF), dietary intake modeling (DIM<0.006496), health risk assessment (HRI<0.028571), and target hazard quotient (THQ<1) analyses showed no potential health hazard associated with the consumption of saffron irrigated with DW and SLW. Therefore, the results of this study provide valuable insights into the optimization of irrigation sources for saffron cultivation.

Heavy metals in meat products from Shandong, China and risk assessment

In this study 13 heavy metals were analysed in representative livestock meat, poultry meat, livestock offal and poultry offal samples (20 per category) from marketplaces and retail stores in 16 cities in Shandong province, China. The investigated heavy metals were Cu, Cr, V, Ni, As, Se, Sn, Cd, Pb, Sb, Mn, Ba and Hg. Results revealed mean levels of total heavy metals in meat and offal of 1.56 mg/kg and 39.8 mg/kg, respectively. Cu, Cr, Mn, Ni, Se, Ba and Pb were found in all samples (100%), followed by Hg (95.0%), V (91.3%), Sn (73.8%), Cd (51.3%), As (21.3%) and Sb (11.3%). Hazard Quotient (HQ) and Hazard Index (HI) values showed that high meat intake can cause potential health risks. Thus, continuous monitoring of health risks and trends of heavy metals in meat products is needed, both for food safety and consumer's health.

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.

Impacts, causes and biofortification strategy of rice selenium deficiency based on publication collection

Selenium (Se) deficiency in rice will result in a Se hidden hunger threat to the general public's human health, particularly in areas where rice consumption is high. Nevertheless, the impact scope and coping strategies have not been given sufficient focus on a worldwide scale. In order to evaluate the impacts, causes and biofortification strategies of Se-deficient rice, this study collected data from the publications on three themes: market survey, field sampling and controlled experiments. According to the market survey, global rice Se concentrations were 0.079 mg/kg on mean and 0.062 mg/kg on median. East Asia has a human Se intake gap due to the region's high rice consumption and the lowest rice Se concentration in markets globally. Total Se concentrations in East Asian paddy soils were found to be adequate based on the field sampling. However, over 70 % of East Asian paddy fields were inadequate to yield rice that met the global mean for rice Se concentration. The Se-deficient rice was probably caused by widespread low Se bioavailability in East Asian paddy fields. There were two important factors influencing rice Se enrichment including root Se uptake and iron oxide in soils. Concentrating on these processes is beneficial to rice Se biofortification. Since Se is adequate in the paddy soils of East Asia. Rather of adding Se exogenously, activating the native Se in paddy soil is probably a more appropriate strategy for rice Se biofortification in East Asia. Meta-analysis revealed water management had the greatest impact on rice Se biofortification. The risks and solutions for rice Se deficiency were discussed in our farmland-to-table survey, which will be a valuable information in addressing the global challenge of Se hidden hunger. This study also provided new perspectives and their justifications, critically analyzing both present and future strategies to address Se hidden hunger.

Removal and recycling of aqueous selenite anions using cobalt-based metal-organic-framework coated on multi-walled carbon nanotubes composite membrane

The utilization of selenium as a novel functional material is rapidly expanding, and the retrieval of selenium from waste containing selenium is gaining recognition in the industry. This study prepared a novel composite membrane coated with the cobalt-based metal-organic framework coated on multi-walled carbon nanotubes (Co-MOF@MWCNTs). The MWCNTs served as the skeleton to support the active components of Co-MOF, which enabled efficient removal and resource utilization of liquid selenite (SeO32-). The morphology, structure, and composition of the prepared membrane were characterized using field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc.. Applying a permeate flux of 67.08 L m-2 h-1, the SeO32- removal efficiency of the composite membrane reached up to 92.2%. The composite membrane containing CoSeO4 can be used as an electrocatalytic oxygen evolution catalyst. Density functional theory calculations and electrochemical analysis showed that the conversion from O* to OOH* was a rate-determining step. Under 1.0 M KOH conditions, the lowest overpotential for Co-MOF@MWCNTs-40 at 10 mA cm-2 was 360 mV. In this study, the process of selenium resource utilization and the mechanism of SeO32- removal by Co-MOF@MWCNTs are revealed. It demonstrates that membrane-based sequestration of SeO32- can provide a viable approach for SeO32- removal and utilization in wastewater.

Topsoil selenium (Se) under Se-rich farming in China: Current status, cropping impacts and ecological risk assessment

Selenium (Se), as an essential microelement, can be supplied through Se-biofortified food from Se-rich soils and associated farming practices for human health, while it can also cause eco-risks if overapplied. In this study, a multi-scale spatiotemporal meta-analysis was conducted to guide sustainable Se-rich farming in China by combining a long-term survey with a reviewed database. The weighted mean concentration, spatial distribution of soil Se, nationwide topsoil Se variation from cropping impacts and its bioavailability-based ecological risks were assessed and quantified. The results showed that the weighted mean content (0.3 mg kg-1) of China was slightly higher than that of previous nationwide topsoil Se surveys, as more Se-rich areas were found in recent high-density sampling surveys. Cropping has overall reduced Se content by 9.5% from farmland across China and deprived more with the increase in farming rotation driven by geo-climatic conditions. Long-term cropping removed Se from Se-rich areas but accumulated it in Se-deficient areas. Additionally, the bioavailable Se content of topsoil in China ranged from 0 to 332 μg kg-1, and the bioavailability-based eco-risks indicated that high eco-risks only existed in overfertilized and extremely high-Se soils, such as in Enshi, Ziyang and some coalfield areas. This work provides evidence for the development of sustainable Se-rich farming with proper utilization of soil Se resources, simultaneously protecting the soil eco-environment.

Effect of Soil Acidification on the Production of Se-Rich Tea

Selenium (Se)-enriched tea is a well-regarded natural beverage that is often consumed for its Se supplementation benefits. However, the production of this tea, particularly in Se-abundant tea plantations, is challenging due to soil acidification. Therefore, this study aimed to investigate the effects of changes in Se under acidified soil conditions. Eight tea plantation soil monitoring sites in Southern Jiangsu were first selected. Simulated acid rain experiments and experiments with different acidification methods were designed and soil pH, as well as various Al-ion and Se-ion concentrations were systematically determined. The data were analyzed using R statistical software, and a correlation analysis was carried out. The results indicated that as the pH value dropped, exchangeable selenium (Exc-Se) and residual selenium (Res-Se) were transformed into acid-soluble selenium (Fmo-Se) and manganese oxide selenium (Om-Se). As the pH increased, exchange state aluminum (Alex) and water-soluble aluminum (Alw) decreased, Fmo-Se and Om-Se declined, and Exc-Se and Res-Se increased, a phenomenon attributed to the weakened substitution of Se ions by Al ions. In the simulated acid rain experiment, P1 compared to the control (CK), the pH value of the YJW tea plantation decreased by 0.13, Exc-Se decreased by 4 ug mg-1, Res-Se decreased by 54.65 ug kg-1, Fmo-Se increased by 2.78 ug mg-1, and Om-Se increased by 5.94 ug mg-1 while Alex increased by 28.53 mg kg-1. The decrease in pH led to an increase in the content of Alex and Alw, which further resulted in the conversion of Exc-Se to Fmo-Se and Om-Se. In various acidification experiments, compared with CK, the pH value of T6 decreased by 0.23, Exc-Se content decreased by 8.35 ug kg-1, Res-Se content decreased by 40.62 ug kg-1, and Fmo-Se content increased by 15.52 ug kg-1 while Alex increased by 33.67 mg kg-1, Alw increased by 1.7 mg kg-1, and Alh decreased by 573.89 mg kg-1. Acidification can trigger the conversion of Exc-Se to Fmo-Se and Om-Se, while the content of available Se may decrease due to the complexation interplay between Alex and Exc-Se. This study provides a theoretical basis for solving the problem of Se-enriched in tea caused by soil acidification.

The importance of selenium in food enrichment processes. A comprehensive review

Selenium is an essential element that determines the proper life functions of human and animal organisms. The content of selenium in food varies depending on the region and soil conditions. Therefore, the main source is a properly selected diet. However, in many countries, there are shortages of this element in the soil and local food. Too low an amount of this element in food can lead to many adverse changes in the body. The consequence of this may also be the occurrence of numerous potentially life-threatening diseases. Therefore, it is very important to properly introduce methods that condition the supplementation of the appropriate chemical form of this element, especially in areas with deficient selenium content. This review aims to summarize the published literature on the characterization of different types of selenium-enriched foods. At the same time, legal regulations and prospects for the future related to the production of food enriched with this element are presented. It should be noted that there are limitations and concerns with the production of such food due to the narrow safety range between the necessary and the toxic dose of this element. Therefore, selenium has been treated with special care for a very long time. For this reason, the presented mechanisms of production processes related to increasing the scale of selenium supplementation should be constantly monitored. Appropriate monitoring and development of the technological process for the production of selenium-enriched food is very important. Such food should ensure consumer safety and repeatability of the obtained product. Understanding the mechanisms and possibilities of selenium accumulation by plants and animals is one of the most important directions in the development of modern bromatology and the science of supplementation. This is particularly important in the case of rational nutrition and supplementing the human diet with an essential element such as selenium. Food technology is facing these challenges today.

Different levels of arsenic exposure through cooked rice and its associated benefit-risk assessment from rural and urban populations of West Bengal, India: a probabilistic approach with sensitivity analysis

Rice arsenic (As) contamination and its consumption poses a significant health threat to humans. The present study focuses on the contribution of arsenic, micronutrients, and associated benefit-risk assessment through cooked rice from rural (exposed and control) and urban (apparently control) populations. The mean decreased percentages of As from uncooked to cooked rice for exposed (Gaighata), apparently control (Kolkata), and control (Pingla) areas are 73.8, 78.5, and 61.3%, respectively. The margin of exposure through cooked rice (MoE_{cooked rice}) < 1 signifies the existence of health risk for all the studied exposed and control age groups. The respective contributions of iAs (inorganic arsenic) in uncooked and cooked rice are nearly 96.6, 94.7, and 100% and 92.2, 90.2, and 94.2% from exposed, apparently control, and control areas. LCR analysis for the exposed, apparently control, and control populations (adult male: 2.1 × 10^-3, 2.8 × 10^-4, 4.7 × 10^-4; adult female: 1.9 × 10^-3, 2.1 × 10^-4, 4.4 × 10^-4; and children: 5.8 × 10^-4, 4.9 × 10^-5, 1.1 × 10^-4) through cooked rice is higher than the recommended value, i.e., 1 × 10^-6, respectively, whereas HQ > 1 has been observed for all age groups from the exposed area and adult male group from the control area. Adults and children from rural area showed that ingestion rate (IR) and concentration are the respective influencing factors towards cooked rice As, whereas IR is solely responsible for all age groups from urban area. A vital suggestion is to reduce the IR of cooked rice for control population to avoid the As-induced health risks. The average intake (μg/day) of micronutrients is in the order of Zn > Se for all the studied populations and Se intake is lower for the exposed population (53.9) compared to the apparently control (140) and control (208) populations. Benefit-risk assessment supported that the Se-rich values in cooked rice are effective in avoiding the toxic effect and potential risk from the associated metal (As).

Dietary Protection against Cognitive Impairment, Neuroinflammation and Oxidative Stress in Alzheimer's Disease Animal Models of Lipopolysaccharide-Induced Inflammation

Alzheimer's disease (AD) is a rapidly growing epidemic with a heavy social and economic burden. Evidence suggests that systemic inflammation, dysregulation of the immune response and the resulting neuroinflammation and neurodegeneration play a significant role in AD pathogenesis. Currently, given that there is no fully convincing cure for AD, the interest in lifestyle factors (such as diet), which potentially delay onset and reduce the severity of symptoms, is increasing. This review is aimed at summarizing the effects of dietary supplementation on cognitive decline, neuroinflammation and oxidative stress in AD-like animal models with a focus on neuroinflammation induced by lipopolysaccharide (LPS) injection, which mimics systemic inflammation in animals. The compounds reviewed include curcumin, krill oil, chicoric acid, plasmalogens, lycopene, tryptophan-related dipeptides, hesperetin and selenium peptides. Despite the heterogeneity of these compounds, there is a strong consensus on their counteracting action on LPS-induced cognitive deficits and neuroinflammatory responses in rodents by modulating cell-signaling processes, such as the NF-κB pathway. Overall, dietary interventions could represent an important resource to oppose AD due to their influence in neuroprotection and immune regulation.

Differences in selenium concentration and bioavailability between paddy and dryland soils of China: A study based on literature collection and field sampling

Lack systematic understanding of differences in environmental behavior of selenium between paddy and dryland soils affects Se biofortification and leads to human Se-related health risks. Therefore, this study investigated differences in Se concentration and bioavailability between paddy and dryland soils using data collected from literatures and field sampling. Our analysis showed paddy soil Se concentration in Se-rich area of China was significantly lower than that in dryland soil. Selenium biological concentration factor of rice grain (BCF_grain) in Se-rich area was lower than that in non-Se-rich area attributed to higher percentage of selenite in available Se. Concentration and percentage of available Se were in dryland soil lower than those in paddy soil and this affected BCF_grain of maize, whereas BCF_grain of rice was further influenced by its Se transport capacity. The ranges of Se concentration in Se-rich paddy (0.14-3.63 mg kg^-1) and dryland (0.45-1.17 mg kg^-1) soils were derived using a linear regression model. The current soil Se concentration evaluation standard was only suitable for dryland but overestimated Se-deficiency and Se-toxicity levels in paddy field. The present study provides theoretical foundations for understanding Se concentrations and bioavailability in soils and selecting efficient and safe approach on cultivated land use.

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.

Iron plaque effects on selenium and cadmium stabilization in Cd-contaminated seleniferous rice seedlings

Dietary intake of selenium (Se)-enriched rice has benefit for avoiding Se-deficient disease, but there is a risk of excessive cadmium (Cd) intake. Through hydroponic culture and adsorption-desorption experiments, this paper focused on Se and Cd uptake in rice seedlings associated with the interactive effects of Se (Se⁴⁺ or Se⁶⁺), Cd, and iron (Fe) plaque. The formation of Fe plaque was promoted by Fe²⁺ and inhibited by Cd but not related with Se species. Shoot Se (Se⁴⁺ or Se⁶⁺) uptake was not affected by Fe plaque in most treatments, except that shoot Se concentrations were decreased by Fe plaque when Se⁴⁺ and Cd co-exposure. Shoot Cd concentrations were always inhibited by Fe plaque, regardless of Se species. Inhibiting Cd adsorption onto root surface (Se⁴⁺  + Cd) or increased Cd retention in Fe plaque (Se⁶⁺  + Cd) is an important mechanism for Fe plaque to reduce Cd uptake by rice. However, we found that DCB Cd concentrations (Cd adsorbed by Fe plaque) were not always positively correlated with Fe plaque amounts and always negatively correlated with the distribution ratios of Cd mass in root to that in Fe plaque (abbreviated as DRCMRF; r =  - 0.942^**); meanwhile, with the increase of DCB Fe concentration, the directions of variations of DCB Cd concentration and DRCMRF were affected by Se species. It indicated that the root system is also an important factor to affect DCB Cd concentration and inhibit Cd uptake, which is mediated by Se species. This paper provides a new understanding of Fe plaque-mediated interactive effect of Se and Cd uptakes in rice, which is beneficial for the remediation of Cd-contaminated and Cd-contaminated seleniferous areas.

Preharvest application of selenite enhances the quality of Chinese flowering cabbage during storage via regulating the ascorbate-glutathione cycle and phenylpropanoid metabolisms

Chinese flowering cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) is a candidate of selenium (Se) accumulator, but it is not clear whether and how preharvest Se treatment affects its quality after harvest. Here, we showed that preharvest application of 100 μmol/L selenite to roots enhanced storage quality of Chinese flowering cabbage. It increased antioxidant capacity and reduced weight loss, leaf yellowing, and protein degradation after harvest. Furthermore, it increased the activities of antioxidant enzymes such as POD, CAT, GSH-Px, and GR, as well as contents of AsA, GSH, phenolics, and flavonoids during storage. Metabolome analysis revealed that phenolic acids including p-Coumaric acid, caffeic acid, and ferulic acid; flavonoids such as naringenin, eriodictyol, apigenin, quercetin, kaempferol, and their derivatives were notably increased by preharvest selenite treatment. Consistently, the total antioxidant capacity, evaluated by DPPH, ABTS, and FRAP methods, were all markedly enhanced in selenite-treated cabbage compared to the control. Transcriptomics analysis showed that the DEGs induced by selenite were significantly enriched in AsA-GSH metabolisms and phenylpropanoids biosynthesis pathways. Moreover, preharvest selenite treatment significantly up-regulated the expressions of BrGST, BrGSH-Px, BrAPX, BrASO, BrC4H, BrCOMT, BrCHS, and BrFLS during storage. These results suggest that preharvest selenite treatment enhanced quality of cabbage not only by increasing Se biological accumulation, but also through regulating AsA-GSH cycle and increasing phenolics and flavonoids synthesis after harvest. This study provides a novel insight into the effects of preharvest Se treatment on quality of Chinese flowering cabbage during storage.

Solid-Water Interface Interaction of Selenium with Fe(II)-Bearing Minerals and Aqueous Fe(II) and S(-II) Ions in the Near-Field of the Radioactive Waste Disposal System

Selenium can be highly toxic in excess for both animals and humans. However, since its mobile forms can be easily adsorbed with ferric minerals, its mobility in the natural oxic environment is generally not an issue. Still, the removal and immobilization of the long-lived radioactive isotope ⁷⁹Se from the contaminated anoxic waters is currently a significant concern. ⁷⁹Se can be accessible in the case of radionuclides' leaching from radioactive waste disposals, where anoxic conditions prevail and where ferrous ions and Fe(II)-bearing minerals predominate after corrosion processes (e.g., magnetite). Therefore, reductive and adsorptive immobilizations by Fe(II)-bearing minerals are the primary mechanisms for removing redox-sensitive selenium. Even though the information on the sorptive interactions of selenium and Fe(II)-bearing minerals seems to be well documented, this review focuses specifically on the state of the available information on the effects of the redox properties of Fe(II)-bearing solid phases (e.g., ferrous oxides, hydroxides, sulfides, and carbonates) on selenium speciation via redox transformation and co-occurring coprecipitation.

Effects of selenium application concentration, period and method on the selenium content and grain yield of Tartary buckwheat of different varieties

BACKGROUND

As a potential selenium-enriched crop, it is of great significance to study the selenium application of Tartary buckwheat. Therefore, to study the effects of selenium application concentration, variety, selenium application period and method on the grain selenium content and yield of Tartary buckwheat, an orthogonal experimental design was used to carry out field experiments in the Jinzhong and Northwest Shanxi ecological regions at the same time. Heifeng 1 and Jinqiao 2 were applied at the branching stage and flowering stage in the Jinzhong, and Heifeng 1 and Jinqiao 6 were applied at the early flowering stage and peak flowering stage in the Northwest Shanxi with different concentrations of sodium selenite (0, 1.37, 2.74, 5.48, 8.22, 12.33, 18.495, 27.7425 g hm^-2 ) by foliar spraying and soil application.

RESULTS

The results showed that the selenium content in Tartary buckwheat grains was positively correlated with the selenium application concentration and increased with increasing selenium application concentration, while the yield of Tartary buckwheat first increased and then decreased with the selenium application concentration. The grain selenium content and yield of Tartary buckwheat were affected by the selenium application concentration, variety and application method.

CONCLUSION

The most effective selenium biofortification program was spraying 2.32 g hm^-2 sodium selenite on the leaves of Heifeng 1 at the early flowering stage in the Jinzhong. In the Northwest Shanxi, spraying 11.01 g hm^-2 sodium selenite on the leaves of Jinqiao 6 at the flowering stage was the most effective selenium biofortification program. © 2022 Society of Chemical Industry.

Emerging roles of selenium on metabolism and type 2 diabetes

Selenium is recognized as an essential element for human health and enters human body mainly via diet. Selenium is a key constituent in selenoproteins, which exert essential biological functions, including antioxidant and anti-inflammatory effects. Several selenoproteins including glutathione peroxidases, selenoprotein P and selenoprotein S are known to play roles in the regulation of type 2 diabetes. Although there is a close association between certain selenoproteins with glucose metabolism or insulin resistance, the relationship between selenium and type 2 diabetes is complex and remains uncertain. Here we review recent advances in the field with an emphasis on roles of selenium on metabolism and type 2 diabetes. Understanding the association between selenium and type 2 diabetes is important for developing clinical practice guidelines, establishing and implementing effective public health policies, and ultimately combating relative health issues.

Advances in Research on the Involvement of Selenium in Regulating Plant Ecosystems

Selenium is an essential trace element which plays an important role in human immune regulation and disease prevention. Plants absorb inorganic selenium (selenite or selenate) from the soil and convert it into various organic selenides (such as seleno amino acids, selenoproteins, and volatile selenides) via the sulfur metabolic pathway. These organic selenides are important sources of dietary selenium supplementation for humans. Organoselenides can promote plant growth, improve nutritional quality, and play an important regulatory function in plant ecosystems. The release of selenium-containing compounds into the soil by Se hyperaccumulators can promote the growth of Se accumulators but inhibit the growth and distribution of non-Se accumulators. Volatile selenides with specific odors have a deterrent effect on herbivores, reducing their feeding on plants. Soil microorganisms can effectively promote the uptake and transformation of selenium in plants, and organic selenides in plants can improve the tolerance of plants to pathogenic bacteria. Although selenium is not an essential trace element for plants, the right amount of selenium has important physiological and ecological benefits for them. This review summarizes recent research related to the functions of selenium in plant ecosystems to provide a deeper understanding of the significance of this element in plant physiology and ecosystems and to serve as a theoretical basis and technical support for the full exploitation and rational application of the ecological functions of selenium-accumulating plants.

Advances in physiological mechanisms of selenium to improve heavy metal stress tolerance in plants

Selenium (Se) is a metalloid mineral nutrient for human and animal health. Plants are the main foodstuff source of the Se intake of humans. For plants, the addition of an appropriate amount of Se could promotes growth and development, and improves the tolerance to environmental stress, especially stress from some of heavy metals (HM) stress, such as cadmium (Cd) and mercury (Hg). This paper mainly reviews and summarizes the physiological mechanism of Se in enhancing HM stress tolerance in plants. The antagonistic effect of Se on HM is a comprehensive effect that includes many physiological mechanisms. Se can promote the removal of excessive reactive oxygen species and reduce the oxidative damage of plant cells under HM elements stress. Se participates in the regulation of the transportation and distribution of HM ions in plants, and alleviates the damage caused by of HM stress. Moreover, Se combine with HM elements to form Se-HM complexes and promote the production of phytochelatins (PCs), thereby reducing the accumulation of HM ions in plants. Overall, Se plays an important role in plant response to HM stress, but current studies mainly focus on physiological mechanism, and further in-depth study on the molecular mechanism is essential to confirm the participation of Se in plant response to environmental stress. This review helps to comprehensively understand the physiological mechanism of Se in plant tolerance against to HM stress of plants, and provides important theoretical support for the practical application of Se in environmental remediation and agricultural development.

Prediction models for monitoring selenium and its associated heavy-metal accumulation in four kinds of agro-foods in seleniferous area

Se-rich agro-foods are effective Se supplements for Se-deficient people, but the associated metals have potential risks to human health. Factors affecting the accumulation of Se and its associated metals in Se-rich agro-foods were obscure, and the prediction models for the accumulation of Se and its associated metals have not been established. In this study, 661 samples of Se-rich rice, garlic, black fungus, and eggs, four typical Se-rich agro-foods in China, and soil, matrix, feed, irrigation, and feeding water were collected and analyzed. The major associated metal for Se-rich rice and garlic was Cd, and that for Se-rich black fungus and egg was Cr. Se and its associated metal contents in Se-rich agro-foods were positively correlated with Se and metal contents in soil, matrix, feed, and matrix organic contents. The Se and Cd contents in Se-rich rice grain and garlic were positively and negatively correlated with soil pH, respectively. Eight models for predicting the content of Se and its main associated metals in Se-rich rice, garlic, black fungus, and eggs were established by multiple linear regression. The accuracy of the constructed models was further validated with blind samples. In summary, this study revealed the main associated metals, factors, and prediction models for Se and metal accumulation in four kinds of Se-rich agro-foods, thus helpful in producing high-quality and healthy Se-rich.

Research Progress on the Effects of Selenium on the Growth and Quality of Tea Plants

Selenium (Se) is an essential trace element for humans and animals, and it plays an important role in immune regulation and disease prevention. Tea is one of the top three beverages in the world, and it contains active ingredients such as polyphenols, theanine, flavonoids, and volatile substances, which have important health benefits. The tea tree has suitable Se aggregation ability, which can absorb inorganic Se and transform it into safe and effective organic Se through absorption by the human body, thereby improving human immunity and preventing the occurrence of many diseases. Recent studies have proven that 50~100.0 mg/L exogenous Se can promote photosynthesis and absorption of mineral elements in tea trees and increase their biomass. The content of total Se and organic selenides in tea leaves significantly increases and promotes the accumulation of polyphenols, theanine, flavonoids, and volatile secondary metabolites, thereby improving the nutritional quality of tea leaves. This paper summarizes previous research on the effects of exogenous Se treatment on the growth and quality of tea trees to provide a theoretical basis and technical support for the germplasm selection and exploitation of Se-rich tea.

The decrease of selenoprotein K induced by selenium deficiency in diet improves apoptosis and cell progression block in chicken liver via the PTEN/PI3K/AKT pathway

Selenoprotein K (SELK) is imperative for normal development of chicken. It does regulate to chicken's physiological function. However, the injury of SELK-deficiency done on chicken liver and its underlying mechanism involved has not yet been covered. Therefore, we built SELK- deficiency model by feeding diet which contained low concentration of selenium (Se) to discuss SELK's regulation mechanism. Through using TUNEL, TEM, western blot and qRT-PCR we found apoptosis occurred in chicken liver in the SELK-deficiency groups. In the meanwhile, our study showed there were differentially expressed of the PTEN/PI3K/AKT pathway, calcium homeostasis, endoplasmic reticulum healthy and cell cycle progression in SELK-deficiency chicken liver tissues. In order to claim the regulation mechanism of SELK, we set SELK-knock down model in the LMH. The results in vitro were coincided with those in vivo. In the SELK-deficiency groups, the PTEN/PI3K/AKT pathway was activated and then induced ERS which eventually resulted in apoptosis in chicken liver. As the same time, the PTEN/PI3K/AKT pathway also regulated the combined effective of MDM2-p53, which leaned liver cells to G1/S blocking. Our findings support the potential of SELK in maintain the health of chicken liver, and indicate that adding proper amount of Se on the daily dietary may alleviate the deficiency of selenium.

Occurrence, distribution, and associations of essential and non-essential elements in the medicinal and edible fungus "Fuling" from southern China

In Asian countries, the sclerotia of the wild-grown fungus Pachyma hoelen ("Fuling"), have been used as food and as medicinal products for centuries. To close the knowledge gaps about the value and possible environmental impacts, the occurrence, distribution, and associations of a range of elements (Ag, Al, As, Ba, Cd, Co, Cr, Cs, Cu, Li, Mg, Mn, Ni, Pb, Rb, Sb, Sr, Tl, U, V, and Zn) were studied in the inner (core) and outer (shell) morphological parts of the sclerotia from a diverse collection in Southern China. Quality of forest and agricultural soil in terms of a geogenic element source and composition can be considered as the main factor determining the occurrence of minerals in sclerotia through the host wood, largely of Pinus yunnanensis, while the anthropogenic impact (basically at remote rural areas of cultivation) in Southern China was negligible. In general, the mean concentration of each element in the outer part was significantly higher than that in the inner part (t-test, p < 0.01), except for Ag. The concentration of a given element in the outer part tended to have a positive relationship with that in the inner part, except for Cu, Se, Ag, and Zn. The elements in different morphological parts of sclerotia present different relation patterns. Compared to the outer part, there were stronger associations of elements in the inner part, suggesting homeostatic regulation of multiple elements in the inner parts. Further study on the sclerotia, infected wood substrate, and surrounding soil from a range of wild sample collections and intentional cultivation should provide a more complex view and allow assessment of the relationship between minerals and bioactive organic compounds produced by P. hoelen.

Assessment of heavy metals should be performed before the development of the selenium-rich soil: A case study in China

The use of selenium (Se)-rich soils in China is an effective method for rural revitalization, but assessment of heavy metals is essential prior to the development of Se-rich soils. This study was focused on the Jiangjin district, a typical Se-rich area located in Sichuan Basin of China, to investigate contamination, influencing factors, and sources of As, Cr, Cu, Cd, Ni, Pb, Sb, and Zn based on 156 topsoil samples. This study analyzed and compared the enrichment factor (EF), Nemerow index (P_N), geographical information system (GIS), and positive matrix factorization (PMF). Results demonstrate that the average values of As, Cu, Cd, Sb, and Zn in topsoil were higher than the soil background values of western Chongqing by approximately 1.75, 1.11, 1.27, 1.71, and 2.58 times, respectively, indicating that some heavy metals have been enriched in the soils. The polluted areas of As, Cu, Cd, and Zn in topsoil were mainly distributed in the northern and central Jiangjin district, whereas high-Sb soils were located in the southeast. The Cr, Cu, Cd, Pb, and Sb were concentrated in Se-rich soils, indicating that heavy metals pollution should be carefully considered for the utilization of Se-rich soils. Four potential sources of heavy metals were found in this study area: 1) the parent materials (Cr, Ni, Cu); 2) industrial activities with high coal consumption (As); 3) mechanical and chemical industrial activities (Zn, Sb); and 4) transportation and agricultural activities (Pb, Cd). These observations provide a scientific basis for the development, utilization, and protection of Se-rich soil resources.

Characteristics of Se in water-soil-plant system and threshold of soil Se in seleniferous areas in Enshi, China

Se-enrichment characteristics in water-soil-plant system and dietary Se status of local residents in seleniferous areas were investigated. Results showed that Se in well water might mainly derived from Se-enriched shales and coals, and Se mobility in seleniferous soils was relatively low with less than 6.7% bioavailable forms in high-Se areas. Soil Se with irrigation, precipitation and fertilization sources contributed more to soil Se than Se-enriched shales and coals in low-Se areas, resulting in slightly higher mobility of Se in low-Se soils. Se concentration in edible parts of main crops ranged from 0.005 mg kg^-1 to 4.17 mg kg^-1, and cereal plants had a higher Se-enrichment ability than tuber plants. The probable dietary Se intake (PDI) in high-Se areas was decreased to 959.3 μg d^-1 in recent years, which might be attributed to tap water as drinking water in recent year rather than well water-dependent and changes in dietary structure, but still far above the permissible value of 400 μg d^-1. Reducing cereal-derived dietary Se intake is an important strategy to better Se nutrition status in high-Se areas. After synthesis considerations on soil Se bioavailability and PDI of Se, the soil total Se of 4 mg kg^-1 and the soil available Se content of 0.32 mg kg^-1 were proposed to be the reference threshold values of soil Se excess in high-Se areas in Enshi, respectively.

Investigation of selenium nutritional status and dietary pattern among children in Kashin-Beck disease endemic areas in Shaanxi Province, China using duplicate portion sampling method

BACKGROUND AND OBJECTIVES

Selenium deficiency is a primary risk factor of Kashin-Beck disease (KBD). This study aimed to investigate whether children in endemic areas could maintain sufficient selenium intake after termination of selenium supplement administration, and evaluate their comprehensive nutritional status and dietary structure.

METHODS

Duplicate portion sampling combined with a questionnaire was adopted to collect data on categories and quantity of all food ingested in three consecutive days. Occipital hair was also collected to detect selenium content by hydride generation atomic fluorescence spectrometry (HGAFS). CDGSS3.0 software and factor analysis were integrated to assess the children's comprehensive nutritional status and dietary structure.

RESULTS

This study included 240 sex-matched (1:1) children aged 7-12 years from KBD endemic (n = 120) and non-endemic (n = 120) areas. Overall, 720 solid food, 720 liquid, and 240 hair samples were collected for selenium determination. The mean selenium level in hair of children in endemic areas (0.38 ± 0.16 mg/kg) was significantly lower than that in children in non-endemic areas (0.56 ± 0.28 mg/kg, Z = -5.249, p < 0.001). The dietary selenium intake of children in endemic areas was 40.0% lower than that in children in non-endemic areas (Z = -9.374, p < 0.001). Children in endemic areas consumed significantly less diverse dietary items leading to significantly less intake of multiple nutrients compared to children in non-endemic areas.

CONCLUSIONS

The dietary selenium intake of most children in endemic areas was less than the recommended amount. The dietary structure of children was undiversified, which limited the intake of multiple nutrients. Therefore, comprehensive nutrition rather than sole selenium intake should be the primary concern in the future.

Transcriptome analysis provides new insight into the distribution and transport of selenium and its associated metals in selenium-rich rice

Selenium is an essential trace element for humans and obtained from diary diets. The consumption of selenium-rich agricultural food is an efficient way to obtain selenium, but the quality and safety of selenium-rich agro-food are always affected by their associated heavy metals, even poses a potential threaten to human health. In this research, a sampling survey of heavy metals contents in selenium-rich rice was conducted, 182 sets of selenium-rich rice samples were collected from five selenium-rich rice-producing areas of China, and the accumulation of selenium and cadmium were found to be associated in rice and soil. Subsequently, a pot experiment was performed in the greenhouse via treating the soil samples with 12 different concentrations of selenium and heavy metals, and the contents of selenium and cadmium in rice grain were confirmed to be significantly associated. Moreover, transcriptome analysis revealed that the up-regulation of transporter-coding may promote the absorption of selenium and cadmium. The expression of antioxidant-coding genes and cadmium chelator transporter coding-genes was up-regulated to reduce the toxicity of cadmium. Meanwhile, the up-regulation of key genes of the ascorbic acid-glutathione metabolic pathway were responsible for the association between selenium and cadmium in Se-rich rice. Our work suggested the correlation between selenium and cadmium accumulation in selenium-rich rice, clarified their accumulation mechanism, provides a direction for the scientific production of selenium-rich agro-foods.

Natural selenium stress influences the changes of antibiotic resistome in seleniferous forest soils

BACKGROUND

Metal(loid)s can promote the spread and enrichment of antibiotic resistance genes (ARGs) in the environment through a co-selection effect. However, it remains unclear whether exposure of microorganisms to varying concentrations of selenium (Se), an essential but potentially deleterious metal(loid) to living organisms, can influence the migration and distribution of ARGs in forest soils.

RESULTS

Precisely 235 ARGs conferring resistance to seven classes of antibiotics were detected along a Se gradient (0.06-20.65 mg kg^-1) across 24 forest soils. (flor)/(chlor)/(am)phenicol resistance genes were the most abundant in all samples. The total abundance of ARGs first increased and then decreased with an elevated available Se content threshold of 0.034 mg kg^-1 (P = 2E-05). A structural equation model revealed that the dominant mechanism through which Se indirectly influences the vertical migration of ARGs is by regulating the abundance of the bacterial community. In addition, the methylation of Se (mediated by tehB) and the repairing of DNA damages (mediated by ruvB and recG) were the dominant mechanisms involved in Se resistance in the forest soils. The co-occurrence network analysis revealed a significant correlated cluster between Se-resistance genes, MGEs and ARGs, suggesting the co-transfer potential. Lelliottia amnigena YTB01 isolated from the soil was able to tolerate 50 μg mL^-1 ampicillin and 1000 mg kg^-1 sodium selenite, and harbored both Se resistant genes and ARGs in the genome.

CONCLUSIONS

Our study demonstrated that the spread and enrichment of ARGs are enhanced under moderate Se pressure but inhibited under severe Se pressure in the forest soil (threshold at 0.034 mg kg^-1 available Se content). The data generated in this pilot study points to the potential health risk associated with Se contamination and its associated influence on ARGs distribution in soil.

Effect of micronutrient selenium on greenhouse gas emissions and related functional genes during goat manure composting

To explore the effect of microelement selenium on greenhouse gas emission, nitrogen loss and related functional genes during the composting. Selenite and selenate were respectively mixed with goat manure and wheat straw and then composted the mixture without selenium regarded as control. The results indicated adding selenite prolonged the thermophilic phase and improved the organic matter degradation, while the selenate presented the opposite results. Selenite and selenate influenced ammonium transformation while prompting the formation of nitrate. Compared to the control, adding selenite and selenate both decreased NH₃ emissions (by 26.7%-53.1%) and increased the total nitrogen content of compost. The addition of selenium increased mcrA in the early phase of composting, thereby promoting CH₄ emission (by 3.5-18.4%). Meanwhile, adding selenate significantly reduced nirK abundance and consequently reduced N₂O emission. Moreover, selenate added treatment presented the highest compost maturity (88.77%) and the lowest global warm potential (117.46 g/kg CO₂-eq.) among all treatments.

Novel Selenium Peptides Obtained from Selenium-Enriched Cordyceps militaris Alleviate Neuroinflammation and Gut Microbiota Dysbacteriosis in LPS-Injured Mice

Increasing attention focuses on the relationship between neuroinflammation and Alzheimer's disease (AD). The reports on the microbiota-gut-brain axis reveal that the regulation by gut microbiota is an effective way to intervene in neuroinflammation-related AD. In this study, two novel selenium peptides (Se-Ps), VPRKL(Se)M (Se-P1) and RYNA(Se)MNDYT (Se-P2), with neuroprotection effects were obtained from Se-enriched Cordyceps militaris. Se-P1 and Se-P2 pre-protection led to a 30 and 33% increase in the PC-12 cell viability compared to the damage group, respectively. Moreover, Se-Ps exhibited a significant pre-protection against LPS-induced inflammatory and oxidative stress in the colon and brain by inhibiting the production of pro-inflammatory mediators (p < 0.05) and malondialdehyde, as well as promoting anti-inflammatory cytokine level and antioxidant enzyme activity (p < 0.05), which may alleviate the cognitive impairment in LPS-injured mice (p < 0.05). Se-Ps not only repaired the intestinal mucosa damage of LPS-injured mice but also had a positive effect on gut microbiota dysbacteriosis by increasing the abundance of Lactobacillus and Alistipes and decreasing the abundance of Akkermansia and Bacteroides. Collectively, the antioxidant, anti-inflammatory, and regulating properties on gut microflora of Se-Ps contribute to their neuroprotection, supporting that Se-Ps could be a promising dietary supplement in the prevention and/or treatment of AD.

The occurrence, transformation and control of selenium in coal-fired power plants: Status quo and development

As a trace element, selenium can cause serious harm to organisms when the concentration is too high. Coal-fired power plants are the main source of man-made selenium emissions. How to control the selenium pollution of coal-fired power plants to realize the renewable selenium and the sustainability of coal has not attracted enough attention from the whole world. This paper outlines the conversion and occurrence of selenium in coal-fired power plants. A small part of the selenium produced by combustion can be removed by selective catalytic reduction (SCR) and electrostatic precipitator (ESP) after the gas phase undergoes physical condensation and chemical adsorption to combine with the particulate matter in the flue gas.Because the chemical precipitation method has poor selenium removal effect, the remaining part enters the flue gas desulfurization absorption tower and can be enriched in the desulfurization slurry. The occurrence situation and conversion pathway of selenium in desulfurization slurry are introduced subsequently, the research progress of selenium removal from wet desulfurization wastewater is reviewed from three aspects: physics, biology and chemistry. We believe that the coupling application of oxidation-reduction potential (ORP) and pH can optimize selenium removal in the desulfurization system by improving the oxidation control. As a technology for wet desulfurization system to treat selenium pollution, it has a good development prospect in near future.Implications: Selenium is a trace element present in coal. It is not only of great significance to the life activities of organisms, but also a kind of rare resource. As the most important source of man-made emissions, coal-fired power plants will cause waste of selenium resources and selenium pollution in the surrounding environment. In this study, the occurrence, conversion and control of selenium in coal-fired power plants were systematically sorted out and analyzed. It is helpful for scholars to study the selenium transformation process more deeply. It is of great significance for policy formulation of recommended control technologies and emission limits. It is of great value for the formulation of recommended control technology and the in-depth study of the selenium transformation process.

Construction of Polygonatum sibiricum Polysaccharide Functionalized Selenium Nanoparticles for the Enhancement of Stability and Antioxidant Activity

Although selenium nanoparticles (SeNPs) have attracted great attention due to their potential antioxidant activity and low toxicity, the application of SeNPs is still restricted by their poor stability. A combination of polysaccharides and SeNPs is an effective strategy to overcome the limitations. In this study, Polygonatum sibiricum polysaccharide (PSP) was used as a stabilizer to fabricate SeNPs under a simple redox system. Dynamic light scattering, transmission electron microscopy, energy dispersive X-ray, ultraviolet-visible spectroscopy, Fourier transform infrared, and X-ray photoelectron spectrometer were applied to characterize the synthesized PSP-SeNPs. The stability and the antioxidant activity of PSP-SeNPs were also investigated. The results revealed that the zero-valent and well-dispersed spherical PSP-SeNPs with an average size of 105 nm and a negative ζ-potential of −34.9 mV were successfully synthesized using 0.1 mg/mL PSP as a stabilizer. The prepared PSP-SeNPs were stable for 30 days at 4 °C. The decoration of the nanoparticle surface with PSP significantly improved the free radical scavenging ability of SeNPs. Compared to the H2O2-induced oxidative stress model group, the viability of PC-12 cells pretreated with 20 μg/mL PSP-SeNPs increased from 56% to 98%. Moreover, PSP-SeNPs exhibited a higher protective effect on the H2O2-induced oxidative damage on PC-12 cells and lower cytotoxicity than sodium selenite and SeNPs. In summary, these results suggest the great potential of PSP-SeNPs as a novel antioxidant agent in the food or nutraceuticals area.

Synergistic inhibitory effect of selenium, iron, and humic acid on cadmium uptake in rice (Oryza sativa L.) seedlings in hydroponic culture

Selenium (Se), iron (Fe), and humic acid (HA) are beneficial fertilizers that inhibit cadmium (Cd) uptake in crops and are crucial for agricultural yields as well as human health. However, the joined effect of Se, Fe, and HA on Cd uptake in rice are still poorly understood. Therefore, a hydroponic culture experiment was established to evaluate the combined effect of Se (Se⁴⁺ or Se⁶⁺), Fe, and HA on the biomass, Cd uptake, and Cd translocation of/in rice seedlings. Compared to Se⁶⁺ application, Se⁴⁺ application in most treatments resulted in lower Cd translocations from roots to shoots, leading to a significant decrease in shoot Cd concentrations. Compared to the treatments with Se⁴⁺ or Fe²⁺ application, joined application of Se⁴⁺ and Fe²⁺ inhibited Cd uptake in shoots by decreasing Cd adsorption onto (iron plaque) and uptake by roots, and alleviating Cd translocation from root to shoot. Compared to the treatments with Se⁶⁺ or Fe²⁺ application, joined application of Se⁶⁺ and Fe²⁺ inhibited Cd uptake in shoots by sequestering (retaining) Cd onto root surface (iron plaque). HA inhibited Cd uptake in all treatments by decreasing the bioavailability of Cd in the nutrient solution through complexation. The simultaneous application of Se, Fe, and HA decreased the shoot Cd concentrations the most, followed by the combined application of two fertilizers and their individual application; the mean shoot Cd concentration in the Fe-SeIV-HA2 treatment was the lowest among all the treatments, at only 11.39 % of those in the control treatments. The 3-way ANOVA results indicated that the Cd concentrations in shoots were significantly affected by Se, Fe, HA, and certain of their interactions (Fe×Se and Se×HA) (p< 0.05). The above findings suggest that the joined application of Se, Fe, and HA ameliorated Cd uptake mainly by inhibiting Cd adsorption onto (iron plaque) and uptake by roots and the translocation from roots to shoots (Fe×Se⁴⁺), retaining (sequestering) Cd in iron plaque (Fe×Se⁶⁺), and decreasing Cd availability in nutrient solution (HA).

The Effect of High Selenite and Selenate Concentrations on Ferric Oxyhydroxides Transformation under Alkaline Conditions

Iron-based nanomaterials have high technological impacts on various pro-environmental applications, including wastewater treatment using the co-precipitation method. The purpose of this research was to identify the changes of iron nanomaterial's structure caused by the presence of selenium, a typical water contaminant, which might affect the removal when the iron co-precipitation method is used. Therefore, we have investigated the maturation of co-precipitated nanosized ferric oxyhydroxides under alkaline conditions and their thermal transformation into hematite in the presence of selenite and selenate with high concentrations. Since the association of selenium with precipitates surfaces has been proven to be weak, the mineralogy of the system was affected insignificantly, and the goethite was identified as an only ferric phase in all treatments. However, the morphology and the crystallinity of ferric oxyhydroxides was slightly altered. Selenium affected the structural order of precipitates, especially at the initial phase of co-precipitation. Still, the crystal integrity and homogeneity increased with time almost constantly, regardless of the treatment. The thermal transformation into well crystalized hematite was more pronounced in the presence of selenite, while selenate-treated and selenium-free samples indicated the presence of highly disordered fraction. This highlights that the aftermath of selenium release does not result in destabilization of ferric phases; however, since weak interactions of selenium are dominant at alkaline conditions with goethite's surfaces, it still poses a high risk for the environment. The findings of this study should be applicable in waters affected by mining and metallurgical operations.

Seaweeds as a “Palatable” Challenge between Innovation and Sustainability: A Systematic Review of Food Safety

Moderate or severe food insecurity affect 2 billion people worldwide. The four pillars of food security (availability, access, use and stability) are in danger due to the impact of climatic and anthropogenic factors which impact on the food system. Novel foods, like seaweeds, have the potential to increase food yields so that to contribute in preventing or avoiding future global food shortages. The purpose of this systematic review was to assess microbiological, chemical, physical, and allergenic risks associated with seaweed consumption. Four research strings have been used to search for these risks. Preferred Reporting Item for Systematic Reviews and Meta-analysis (PRISMA) guidelines were applied. Finally, 39 articles met the selected criteria. No significant hazards for microbiological, allergenic, and physical risks were detected. Regarding chemical risk, algae can accumulate various heavy metals, especially when harvested in polluted sites. Cultivating seaweeds in a controlled environment allows to avoid this risk. Periodic checks will be necessary on the finished products to monitor heavy metals levels. Since the consumption of algae seems to be on the rise everywhere, it seems to be urgent that food control authorities establish the safety levels to which eating algae does not represent any risk for human health.

Effects of selenate on Se, flavonoid, and glucosinolate in broccoli florets by combined transcriptome and metabolome analyses

Broccoli is a nutritious vegetable popular all over the world. This study investigated the effects of different concentrations of selenate (0, 0.1, 0.2, 0.4, 0.8, and 1.6 mmol/L) on the selenium (Se), glucosinolate, and flavonoid contents of broccoli florets. Results showed that the total Se, selenomethionine, and methyl selenocysteine contents increased following selenate dosage. Interestingly, selenate treatment of 0.4 mmol/L decreased the flavonoid but increased the glucosinolate content. Metabolome analysis revealed changes in the individual contents of glucosinolates and flavonoids. Conjoint analysis of transcriptome and metabolome showed that the glucosinolate and flavonoid compounds were potentially regulated by two sulfate transporter genes (Sultr3;1 and Sultr4;2) and several cytochrome P450 genes (e.g., CYP71B21, CYP72C1, and CYP81F1). These new findings indicated that Se treatment may influence glucosinolate and flavonoid accumulation by regulating the expression of these genes. The results of this study provide some novel insights into the effects of Se on glucosinolates and flavonoids in broccoli florets and deepen our understanding of the regulatory network between some specific genes and these compounds.