Selenium biofortification and its effect on multi-element change in Auricularia auricular

Insight into selenium biofortification and the selenite metabolic mechanism of Monascus ruber M7

Monascus species are functional fermentation fungi with great potential for selenium (Se) supplementation. This study investigated the effects of Se bio-fortification on the growth, morphology, and biosynthesis of Monascus ruber M7. The results demonstrated a significant increase in the yield of orange and red Monascus pigments (MPs) in red yeast rice (RYR) by 38.52% and 36.57%, respectively, under 20 μg/mL of selenite pressure. Meanwhile, the production of citrinin (CIT), a mycotoxin, decreased from 244.47 μg/g to 175.01 μg/g. Transcriptome analysis revealed significant upregulation of twelve genes involved in MPs biosynthesis, specifically MpigE, MpigF, and MpigN, and downregulation of four genes (mrr3, mrr4, mrr7, and mrr8) associated with CIT biosynthesis. Additionally, three genes encoding cysteine synthase cysK (Log2FC = 1.6), methionine synthase metH (Log2FC = 2.2), and methionyl-tRNA synthetase metG (Log2FC = 1.8) in selenocompound metabolism showed significantly upregulated. These findings provide insights into Se biotransformation and metabolism in filamentous fungi.

Effects of nanoselenium on the performance, blood indices, and milk metabolites of dairy cows during the peak lactation period

To compare the impact of nanoselenium and sodium selenite on the performance, blood indices, and milk metabolites of dairy cows during the peak lactation period, two groups of dairy cows under the same conditions were selected as the control group (CON group) and treatment group (NSe group) for a 38-day (10 days for adaptation and 28 days for sampling) experiment. The control group (CON) was provided a basal diet +3.3 g/d of sodium selenite (purity1%), whereas the nanoselenium group (NSe) was offered the same diet +10 mL/d of nanoselenium (selenium concentration 1,500 mg/L). The results showed that NSe significantly increased the milk yield, milk selenium content, and feed efficiency (p < 0.05), but had no significant effect on other milk components (p > 0.05). NSe significantly increased blood urea nitrogen (BUN) and alkaline phosphatase (ALP) (p < 0.05), but had no significant effects on malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), blood total antioxidant capacity (T-AOC), or blood selenium (p > 0.05). In addition, the nontargeted metabolomics of the milk was determined by LC-MS technology, and the differentially abundant metabolites and their enrichment pathways were screened. According to these findings, NSe considerably increased the contents of cetylmannoside, undecylenoic acid, 3-hydroxypentadecanoic acid, 16-hydroxypentadecanoic acid, threonic acid, etc., but decreased the contents of galactaric acid, mesaconic acid, CDP-glucose etc. Furthermore, the enriched metabolic pathways that were screened with an impact value greater than 0.1 included metabolism of niacin and niacinamide, pyruvate, citrate cycle, riboflavin, glycerophospholipid, butanoate and tyrosine. Pearson correlation analysis also revealed a relationship between different milk metabolites and blood selenium, as well as between milk selenium and blood biochemical indices. In conclusion, compared with sodium selenite, nanoselenium improves the milk yield, feed efficiency, and milk selenium content of dairy cows and regulates milk metabolites and related metabolic pathways in Holstein dairy cows during the peak lactation period, which has certain application prospects in dairy production.

Screening and Identification of Soil Selenium-Enriched Strains and Application in Auricularia auricula

Selenium (Se) is an essential trace element for human physiological metabolism. The application of organic Se as a source to cultivate Se-rich plants for micronutrient supplementation has been receiving increasing attention. In our study, a bacterial strain named H1 was isolated from the soil in Heilongjiang Province, China, and under optimal culture conditions, the unit Se content could reach 3000 μg·g-1 and its 16S ribosomal DNA sequence seemed to be a new molecular record of an Enterobacter species. After the domestication of Se tolerance and Se-rich experiments, H1 can be used as a Se source for cultivation of Se-rich Auricularia auricula. The results showed that soluble protein, soluble sugar, free amino acid and vitamin C contents in Auricularia auricula were notably increased by 28.7%, 21.8%, 32.5% and 39.2% under the treatment of Se concentration of 0.24 mg·kg-1, respectively. These findings enhance our understanding that H1 is more conducive to Se uptake and nutrient accumulation.

Agronomic and Genetic Strategies to Enhance Selenium Accumulation in Crops and Their Influence on Quality

Selenium (Se) is an essential trace element that plays a crucial role in maintaining the health of humans, animals, and certain plants. It is extensively present throughout the Earth's crust and is absorbed by crops in the form of selenates and selenite, eventually entering the food chain. Se biofortification is an agricultural process that employs agronomic and genetic strategies. Its goal is to enhance the mechanisms of crop uptake and the accumulation of exogenous Se, resulting in the production of crops enriched with Se. This process ultimately contributes to promoting human health. Agronomic strategies in Se biofortification aim to enhance the availability of exogenous Se in crops. Concurrently, genetic strategies focus on improving a crop's capacity to uptake, transport, and accumulate Se. Early research primarily concentrated on optimizing Se biofortification methods, improving Se fertilizer efficiency, and enhancing Se content in crops. In recent years, there has been a growing realization that Se can effectively enhance crop growth and increase crop yield, thereby contributing to alleviating food shortages. Additionally, Se has been found to promote the accumulation of macro-nutrients, antioxidants, and beneficial mineral elements in crops. The supplementation of Se biofortified foods is gradually emerging as an effective approach for promoting human dietary health and alleviating hidden hunger. Therefore, in this paper, we provide a comprehensive summary of the Se biofortification conducted over the past decade, mainly focusing on Se accumulation in crops and its impact on crop quality. We discuss various Se biofortification strategies, with an emphasis on the impact of Se fertilizer strategies on crop Se accumulation and their underlying mechanisms. Furthermore, we highlight Se's role in enhancing crop quality and offer perspective on Se biofortification in crop improvement, guiding future mechanistic explorations and applications of Se biofortification.

Effect of Selenium-Enriched Substrate on the Chemical Composition, Mineral Bioavailability, and Yield of Edible Mushrooms

Mushrooms absorb minerals from substrates in which they are cultivated, so they could be used as vehicles of minerals that are deficient in human or animal diets, such as selenium. Selenium deficiency aggravates cardiovascular diseases, diabetes mellitus, and intestinal cancer. This work presents the latest discoveries related to the production of edible mushrooms in selenium-enriched substrates and discusses their use as an alternative to supply the deficiency of this mineral in human and animal diets. Selenized mushrooms and their derived extracts present bioaccessible and bioavailable forms of selenium, as antioxidant and antitumor activity, as demonstrated in various in vitro and in vivo experiments. Consequently, the consumption of these mushrooms reduces the levels of blood cholesterol and glucose. On the other hand, growing mushrooms in selenium-enriched substrates may alter the yield and their chemical composition, and this lack of standardization is still an obstacle to the scale up of the production process. On the other hand, the use of agro-industrial by-products as substrates can enable the cultivation of enriched edible mushrooms and their commercialization.

Interactive Effects of Selenium, Zinc, and Iron on the Uptake of Selenium in Mycelia of the Culinary-Medicinal Winter Mushroom Flammulina velutipes (Agaricomycetes)

The present study for the first time addressed whether the simultaneous presence of selenium, zinc and iron may have effects on the selenium uptake in the mycelia of the winter mushroom (also known as enoki), Flammulina velutipes. Response surface methodology was used to optimize concentrations of selenium, zinc and iron in the range of 0 to 120 mg L-1. The findings showed that application of selenium, zinc and iron (singly, in pairs, or triads) significantly enhanced the selenium accumulation in the mycelia. The highest amount of the selenium accumulation was observed when selenium (60 mg L-1) and zinc (120 mg L-1) were applied into submerged culture media, concurrently, leading to an 85-fold and 88-fold increase in the selenium content of the mycelia compared to that of the mycelia treated with selenium only and untreated mycelia, respectively. In addition, accumulation of selenium into the mycelia had no deteriorative effects on the mycelial biomass. The findings presented in this study may have implications for daily nutrition and industrial bioproduction of mushroom mycelia enriched with selenium.

Effects of selenate and selenite on selenium accumulation and speciation in lettuce

Lettuce is a common vegetable in hydroponic production. In this paper, a selenium (Se)-biofortification method was provided. The Se content, speciation, and the effects of different concentrations of selenate and selenite on lettuce growth and amino acids were investigated. The results showed that lettuce had strong ability to accumulate exogenous selenium, and inorganic Se could be effectively converted into organic Se. The proportion of organic Se in the shoots under treatment with 4 μmol L-1 selenite was 100%. Selenomethionine was the main organic Se, accounting for 51% (selenate) and 90% (selenite) of the total Se. Adding Se improves photosynthesis of lettuce and promotes growth. The growth with 2 μmol L-1 selenate and 4 μmol L-1 selenite was better than CK, and the shoot fresh weight was increased by 143.22% and 166.98%, respectively. Furthermore, the optimum Se application is 2 μmol L-1, and some areas can apply 4 μmol L-1 selenite. But Se-excessive areas are not recommended to grow selenium-rich foods. Therefore, lettuce has strong biofortification potential.

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.

Effects of Se(IV) or Se(VI) enrichment on proteins and protein-bound Se distribution and Se bioaccessibility in oyster mushrooms

A successful mushroom enrichment process must produce foods that have compounds potentially absorbed by the human body. In this study, Pleurotus ostreatus and Pleurotus djamor mushrooms were grown on organic substrate supplemented with different Se(IV) and Se(VI) concentrations, and evaluated in the following features: Fruiting bodies morphology; Se uptake and accumulation; Distribution of proteins and protein-bound Se; Se species identification on enzymatic extracts; Se bioaccessibility; and Distribution of bioaccessible protein-bound Se. Pleurotus djamor grown on Se(IV)-supplemented substrate showed the greatest potential to uptake and accumulate Se. For Se species screening, selenomethionine was identified in white oyster mushroom, while selenomethionine, selenocystine, and Se-methylselenocysteine in pink oyster mushrooms. In soluble fractions from in vitro gastrointestinal digestion assays, Se showed high bioaccessibility (>94%). Lastly, bioaccessible Se species were found to be mainly associated to LMW (<17 kDa) in Pleurotus ostreatus (74%) and Pleurotus djamor (68%) grown on Se(IV)-supplemented substrates.

Selenium biofortification in Pleurotus eryngii and its effect on lead adsorption of gut microbiota via in vitro fermentation

It is of great significance to develop safe and efficient dietary selenium sources to improve lead toxicity. In this study, selenate, selenite, SeMet and Se-yeast were supplied to investigate the Se biofortification and bioaccessibility in Pleurotus eryngii. The effects of Se-enriched P. eryngii on lead binding bacteria were investigated via in vitro fermentation. With 40 mg/kg Se in the substrate, the total Se contents of P. eryngii treated with selenite and Se-yeast were 145.22 ± 8.00 mg/kg and 90.01 ± 7.01 mg/kg, respectively. Compared with selenite, Se-yeast treatment significantly increased the organic Se proportion in P. eryngii (SeCys₂ 2.85 ± 0.17%, MeSeCys 2.33 ± 0.21% and SeMet 78.19 ± 1.58%), which led to higher bioaccessibility. With 1 mg/L lead treatment during in vitro fermentation, Se-enriched P. eryngii promoted the growth of Desulfovibrio, which contributed to the increase of gut microbiota lead adsorption. Se-enriched P. eryngii cultivated with Se-yeast could be used as dietary Se sources for lead toxicity improvement.

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.

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.

Influence of Selenium Biofortification on the Growth and Bioactive Metabolites of Ganoderma lucidum

Selenium biofortification of edible and medicinal mushrooms is an effective way to produce selenium-enriched food supplements. Ganoderma lucidum is the typical one with excellent biological activity. This study investigated G. lucidum growth and bioactive metabolites alterations during liquid culture with different concentrations of selenite. Low selenium levels did not affect growth and mycelia morphology, whereas high selenium levels negatively influenced growth, dramatically decreased biomass, caused nucleic acid and protein leakage, damaged cell walls and membranes, and resulted in indicators such as degraded cells, a red color, and an unpleasant odor. Through headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis, ten volatile Se compounds were identified in G. lucidum with 200 ppm selenite, which led to an odor change, whereas only three with 50 ppm selenite. SeMet was the major selenoamino acid in the 50 ppm selenite group by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS), but more MeSeCys was produced with 200 ppm selenite. Polysaccharide yields were promoted and inhibited with 50 and 200 ppm selenite, respectively. These results provide comprehensive insights into the effects of selenite on G. lucidum in liquid culture and are beneficial for functional selenium-enriched mushroom production and improving nutritive values.

Uptake, transport, and metabolism of selenium and its protective effects against toxic metals in plants: a review

Selenium (Se) is an essential trace element of fundamental importance to humans, animals, and plants. However, the uptake, transport, and metabolic processes of Se and its underlying mechanisms in plants have not been well characterized. Here, we review our current understanding of the adsorption and assimilation of Se in plants. First, we discussed the conversion of Se from inorganic Se into organic forms, the mechanisms underlying the formation of seleno-amino acids, and the detoxification of Se. We then discussed the ways in which Se protects plants against toxic metal ions in the environment, such as by alleviating oxidative stress, regulating the activity of antioxidant enzymes, sequestering metal ions, and preventing metal ion uptake and accumulation. Generally, this review will aid future research examining the molecular mechanisms underlying the antagonistic relationships between Se and toxic metals in plants.

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.

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.

Effects of different exogenous selenium on Se accumulation, nutrition quality, elements uptake, and antioxidant response in the hyperaccumulation plant Cardamine violifolia

Cardamine violifolia (Brassicaceae) is a novel selenium(Se) hyperaccumulation plant with rich nutrients, and serves as a good source of special vegetables in Enshi, China. The present study aimed to investigate the effects of the application of selenate, selenite, and Se yeast (50-800 mg/L) on the growth, Se accumulation, nutrient uptake, and antioxidant response of C. violifolia. The results showed that the Se accumulation efficiency was selenate > selenite > Se yeast, the maximum Se concentration could achieve over 7000 mg/kg, and about 90% was organic Se. The major Se speciation found was mainly SeCys₂ and the proportion of various Se species were affected by the Se forms and concentrations. Besides, the plant growth, nutrition quality indexes, element uptakes, and antioxidant responses indicated that 200 mg/L selenate was optimum for C. violifolia to accumulate Se without much impacts, while to obtain more proportion of organic Se, 200 mg/L selenite might be a better choice.

Influence of processing methods and exogenous selenium species on the content and in vitro bioaccessibility of selenium in Pleurotus eryngii

Understanding the effects of processing on the Se content and bioaccessibility in food is critical in guiding the development of Se-enriched products. In this study, Se-enriched Pleurotus eryngii was obtained by applying different Se supplements to the substrate. Selenium content and its bioaccessibility among raw and processed fruit bodies were compared. The application of exogenous Se had no significant effect on the yield of P. eryngii, while amendment Se yeast could slightly promote the growth of P. eryngii. The enrichment ability of P. eryngii among different Se supplements declined in the order of Na₂SeO₃ > Se yeast > Na₂SeO₄. However, the processing treatments resulted in 6.6%-45.9% Se loss. The Se bioaccessibility of P. eryngii was 78.4%-89.7%. Frying treatment reduced Se bioaccessibility in samples, whereas boiling treatment enhanced it. Therefore, Se yeast and boiling treatment are recommended as the ideal Se supplement and processing method for Se-enriched P. eryngii.

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.

Selenium in plant foods: speciation analysis, bioavailability, and factors affecting composition

Interest in selenium has been increasing over the past few decades with growing knowledge of its importance to overall health. The ability of several plants to accumulate and transform inorganic selenium forms into its bioactive organic compounds has important implications for human nutrition and health. In this review, we present the studies carried out during the last decade to characterize selenium species produced by different plant foods. Attention is also paid to the effect of selenium treatment on chemical composition and antioxidant properties of plants.