Selenium Biofortification Impacts the Nutritive Value, Polyphenolic Content, and Bioactive Constitution of Variable Microgreens Genotypes

Selenium dynamics in plants: Uptake, transport, toxicity, and sustainable management strategies

Selenium (Se) plays crucial roles in human, animal, and plant physiology, but its varied plant functions remain complex and not fully understood. While Se deficiency affects over a billion people worldwide, excessive Se levels can be toxic, presenting substantial risks to ecosystem health and public safety. The delicate balance between Se's beneficial and harmful effects necessitates a deeper understanding of its speciation dynamics and how different organisms within ecosystems respond to Se. Since humans primarily consume Se through Se-rich foods, exploring Se's behavior, uptake, and transport within agroecosystems is critical to creating effective management strategies. Traditional physicochemical methods for Se remediation are often expensive and potentially harmful to the environment, pushing the need for more sustainable solutions. In recent years, phytotechnologies have gained traction as a promising approach to Se management by harnessing plants' natural abilities to absorb, accumulate, metabolize, and volatilize Se. These strategies range from boosting Se uptake and tolerance in plants to releasing Se as less toxic volatile compounds or utilizing it as a biofortified supplement, opening up diverse possibilities for managing Se, offering sustainable pathways to improve crop nutritional quality, and protecting human health in different environmental contexts. However, closing the gaps in our understanding of Se dynamics within agricultural systems calls for a united front of interdisciplinary collaboration from biology to environmental science, agriculture, and public health, which has a crucial role to play. Phytotechnologies offer a sustainable bridge between Se deficiency and toxicity, but further research is needed to optimize these methods and explore their potential in various agricultural and environmental settings. By shedding light on Se's multifaceted roles and refining management strategies, this review contributes to developing cost-effective and eco-friendly approaches for Se management in agroecosystems. It aims to lead the way toward a healthier and more sustainable future by balancing the need to address Se deficiency and mitigate the risks of Se toxicity.

Simultaneous biofortification of vitamin C and mineral nutrients in arugula microgreens

Microgreens have shown promise in improving the overall nutritional value of diets due to their high nutrient density. Agronomic biofortification, is an efficient strategy for enhancing the nutritional value of crops, including microgreens. This study aimed to biofortify vitamin C and other essential nutrients in arugula microgreens using four treatments containing 0.25 % ascorbic acid, pH adjusted with different bases: KOH, Ca(OH)2, ZnCO3, or NaOH and a deionized water control. The results indicate that ascorbic acid-treated microgreens had more vitamin C, greater fresh weight and % dry matter than the control. The ascorbic acid + Zn treatment had an 135 % average increase in vitamin C compared to the control. Microgreens treated with ascorbic acid also showed increased levels of minerals that are present in the nutrient solution, such as potassium, sodium, calcium, and zinc. This research contributes to the growing interest in microgreens biofortification and their role in addressing multi-nutrient deficiencies.

Biofortification and Valorization of Celery byproducts Using Selenium and PGPB under Reduced Nitrogen Regimes

Due to climate change and exacerbated population growth, the search for new sustainable strategies that allow for greater food productivity and that provide greater nutritional quality has become imperative. One strategy for addressing this problem is the combined use of fertilization with a reduced dose of nitrogen and biostimulants. Celery processing produces a large amount of waste with its concomitant pollution. Therefore, it is necessary to address the valorization of its byproducts. Our results revealed reductions in the biomass, Na, P, Mn, B, sugars, and proteins in the byproducts and increased lipid peroxidation, Fe (all celery parts), and K (byproducts) when the N supplied was reduced. Plants inoculated with Azotobacter salinestris obtained a greater biomass, a higher accumulation of K (byproducts), a build-up of sugars and proteins, reduced concentrations of P, Cu, Mn, B, Fe (petioles), and Zn (byproducts), and reduced lipid peroxidation. The application of Se at 8 μM reinforced the beneficial effect obtained after inoculation with Azotobacter salinestris. In accordance with our results, edible celery parts are recommended as an essential ingredient in the daily diet. Furthermore, the valorization of celery byproducts with health-promoting purposes should be considered.

Phytochemical Profile, Bioactive Properties, and Se Speciation of Se-Biofortified Red Radish (Raphanus sativus), Green Pea (Pisum sativum), and Alfalfa (Medicago sativa) Microgreens

The impact of selenium (Se) enrichment on bioactive compounds and sugars and Se speciation was assessed on different microgreens (green pea, red radish, and alfalfa). Sodium selenite and sodium selenate at a total concentration of 20 μM (1:1) lead to a noticeable Se biofortification (40-90 mg Se kg-1 DW). In green pea and alfalfa, Se did not negatively impact phenolics and antioxidant capacity, while in red radish, a significant decrease was found. Regarding photosynthetic parameters, Se notably increased the level of chlorophylls and carotenoids in green pea, decreased chlorophyll levels in alfalfa, and had no effect on red radish. Se treatment significantly increased sugar levels in green pea and alfalfa but not in red radish. Red radish had the highest Se amino acid content (59%), followed by alfalfa (34%) and green pea (28%). These findings suggest that Se-biofortified microgreens have the potential as functional foods to improve Se intake in humans.

A decade of improving nutritional quality of horticultural crops agronomically (2012-2022): A systematic literature review

The ultimate goal of world crop production is to produce more with less to meet the growing population demands. However, concentrating solely on increased quantity of production often impacts the quality of produce. Consumption of crops or foods that do not meet nutritional or dietary needs can lead to malnutrition. Malnutrition and undernutrition are prevalent in a significant portion of the population. Agronomic biofortification of minerals and vitamins in horticultural crops has emerged as a promising approach to address nutrient deficiencies and enhance the nutritional quality of food. Despite numerous research papers on plant nutrient biofortification, there remains a lack of systematic reviews that comprehensively summarize the latest knowledge on this topic. Herein we discuss different agronomic ways to biofortify several horticultural crops over the past decade. This systematic review aims to fill this gap by presenting various methodologies and comparing the outcomes of these methods in respect to nutrient content in plant parts. The review focuses on original research papers collected from various scientific databases including Scopus and Web of Knowledge, covering the most recent literature from the last ten years (2012-2022) for specific studies on the agronomic biofortification macronutrients, micronutrients, and vitamins in horticultural plants with exclusion of certain criteria such as 'genetic,' 'breeding,' and 'agronomic crops.' This review critically analyzes the current state of research and explores prospects for the future in this field. The biofortification of various minerals and vitamins, including calcium, selenium, iodine, B vitamins, vitamin A, and vitamin C, are examined, highlighting the achievements and limitations of existing studies. In conclusion, agronomic biofortification of minerals and vitamins in horticultural crops with further research offers a promising approach to address nutrient deficiencies and improve the nutritional quality of food.

Selenium biofortification of microgreens: Influence on phytochemicals, pigments and nutrients

Kale (Brassica oleracea L. var. sabellica L.), kohlrabi (Brassica oleracea L. var. gongylodes L.) and wheat (Triticum aestivum L. cv. Bancal) microgreens were cultivated in presence of selenium 20 μmol L-1 as sodium selenite and sodium selenate mixture. The influence of this biofortification process was evaluated in terms of biomass production, total Se, macro- and micronutrients concentration, polyphenols, antioxidant activity, chlorophylls and carotenoids levels and total soluble proteins content. The results obtained have shown a significant concentration of total Se in the biofortified microgreens of kale (133 μg Se·g-1 DW) and kohlrabi (127 μg Se·g-1 DW) higher than that obtained for wheat (28 μg Se·g-1 DW). The Se uptake in all the species did not produce oxidative damage to the plants reflected in the bioactive compounds, antioxidant capacity or pigments concentration. These Se-enriched microgreens may contribute to the recommended intake of this nutrient in human diet as to overcome Se-deficiency.

Selenium biofortification improves bioactive composition and antioxidant status in Plantago ovata Forsk., a medicinal plant

BACKGROUND

Selenium (Se) is an essential micronutrient for humans, but its deficiency as well as toxicity affects large number of people worldwide. Plantago ovata, a commercially important medicinal plant, is mainly cultivated in western regions of India, where elevated levels of Se have been found in soil. Thus, we evaluated the potential of Se biofortification in P. ovata via phytoremediation and its effect on the bioactive composition.

RESULTS

The results showed a significant alteration in various morphological and physiological parameters in a dose-dependent manner. The 10 µM Se dose improved seedling height, biomass and total chlorophyll content. There was a gradual increase in total Se content, with highest accumulation of 457.65 µg/g FW at 500 µM Se treatment. Se positively affected the antioxidative metabolism which was measured from the change in total antioxidant capacity, radical scavenging activity and Metallothionein 2 expression. Increasing levels of Se also affected the PAL activity, total polyphenol and flavonoid content. Caffeic acid, Coumaric acid and Rutin were found to be the most abundant phenolic compounds.

CONCLUSIONS

Low levels of selenium (below 50 µM) can successfully improve Se accumulation and elicit production of various polyphenols without hampering plant growth. Thus, Se fortification of P. ovata seedlings via phytoremediation appears to be a feasible and efficient way to enhance its nutraceutical value in dietary products.

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.

Biochemical Compounds, Antioxidant Capacity, Leaf Color Profile and Yield of Basil (Ocimum sp.) Microgreens in Floating System

Basil is a great source of phytochemicals such as polyphenols, vitamin C, anthocyanin, and flavonoids. In this work, the biochemical compounds, antioxidant capacity, leaf color profile, and yield of 21 cultivars and genotypes of basil microgreen were investigated. Results showed that the highest antioxidant potential composite index (APCI) was measured in Persian Ablagh genotype (70.30). Twenty-one basil genotypes were classified into four clusters, including cluster 1 (lowest antioxidant capacity and total phenolic compounds), cluster 2 (lowest anthocyanin, vitamin C and APCI index), cluster 3 (highest vitamin C, total phenolic compounds, antioxidant capacity and APCI index), and cluster 4 (highest levels of anthocyanin). The principal components analysis (PCA) of basil genotypes showed diversity in terms of phytochemical components, and F1, F2, F3, and F4 explained the variation at the rate of 78.12%. The average annual temperature of the origin of basil seeds plays an important role in the synthesis of antioxidant content. Most of the seeds with moderate origin had a higher APCI index. The Persian Ablagh genotype, Violeto, and Kapoor cultivars can be recommended, according to their APCI index and yield. These cultivars can be used individually or in different ratios to produce different biochemical substances with different concentrations for various purposes.

Iodine-Biofortified Microgreens as High Nutraceutical Value Component of Space Mission Crew Diets and Candidate for Extraterrestrial Cultivation

The success of Space missions and the efficacy of colonizing extraterrestrial environments depends on ensuring adequate nutrition for astronauts and autonomy from terrestrial resources. A balanced diet incorporating premium quality fresh foods, such as microgreens, is essential to the mental and physical well-being of mission crews. To improve the nutritional intake of astronaut meals, two levels of potassium iodide (KI; 4 µM and 8 µM) and an untreated control were assessed for iodine (I) biofortification, and overall nutraceutical profile of four microgreens: tatsoi (Brassica rapa L. subsp. narinosa), coriander (Coriandrum sativum L.), green basil, and purple basil (Ocimum basilicum L.). A dose-dependent increase in I was observed at 8 µM for all species, reaching concentrations of 200.73, 118.17, 93.97, and 82.70 mg kg^-1 of dry weight, in tatsoi, coriander, purple basil, and green basil, respectively. Across species, I biofortification slightly reduced fresh yield (-7.98%) while increasing the antioxidant activity (ABTS, FRAP, and DPPH). LC-MS/MS Q extractive orbitrap analysis detected 10 phenolic acids and 23 flavonoids among microgreen species. The total concentration of phenolic acids increased (+28.5%) in purple basil at 8 µM KI, while total flavonoids in coriander increased by 23.22% and 34.46% in response to 4 and 8 µM KI, respectively. Both doses of KI increased the concentration of total polyphenols in all species by an average of 17.45%, compared to the control.

Transcriptome and physiological determination reveal the effects of selenite on the growth and selenium metabolism in mung bean sprouts

Selenium (Se) biofortification of crops has been studied to substantially improve the Se content in human dietary food intake. In the present study, Vigna radiata (mung bean) seeds were soaked in different concentrations of sodium selenite (Na₂SeO₃). Low concentration of selenite is conducive to seed germination and growth, and can increase the fresh weight (FW) and dry weight (DW) of sprouts. The concentration of Na₂SeO₃ lower than 50 mg/kg resulted in noticeable elongation in the stem and marginal elongation in root. Mung bean seeds soaked with 80 mg/kg Na₂SeO₃ accounted for 93.77% of organic Se after growing for about 5 days. Transcriptome data revealed that Se treatment enhances starch and sugar metabolism, along with the up-regulation of ribosomal protein and DNA synthesis related genes. Further analysis indicated that the mung bean seeds absorbed Na₂SeO₃ through PHT1.1 and NIP2. Se (IV) was transformed into Se (VI) and transported to stems, leaves and roots through cotyledons during the germination of bean sprouts. SULTR3;3 may play an important role in the transit process. Se (VI) or Se (IV) transported to the leaves was catalytically transformed into SeCys through SiR and CS, and SeCys is further converted to MeSeCys through SMT. Most SeCys were transformed into SeHCys through CBL, transported to plastids, and finally transformed into SeMet through Met Synthase.

Vitamin C biofortification of broccoli microgreens and resulting effects on nutrient composition

The consumption of plants plays an important role in human health. In addition to providing macro and micronutrients, plants are the sole sources of several phytonutrients that play a major role in disease prevention. However, in modern diets, increased consumption of cheaper, processed foods with poor nutritional value over fruits and vegetables leads to insufficient consumption of essential nutrients such as vitamin C. Taking supplements can address some of the insufficient nutrients in a diet. However, supplements are not as diverse or bioavailable as the nutrients in plants. Improving the abundance of nutrients in plants will reduce the amounts that need to be consumed, thereby reducing the price barrier and use of supplements. In this study, broccoli (Brassica oleracea var. italica) microgreens grown in a controlled environment were biofortified for increased vitamin C content. The microgreens grown on growing pads were treated with supplemental nutrient solutions. Treatments were applied four to five days after germination and included four different concentrations of ascorbic acid specifically, 0% (control), 0.05%, 0.1%, 0.25% and 0.5%, added to the nutrient solution. Microgreens with turgid cotyledons and appearance of tip of first true leaves were harvested about 14 days after germination and were analyzed for biomass, chlorophylls, carotenoids, vitamin C and other minerals content. The ascorbic acid improved the microgreens' fresh biomass, percent dry matter, chlorophylls, carotenoids, vitamin C, and potassium content. Moreover, this study also mapped out the correlation between ascorbic acid, phytochemicals, and broccoli microgreens' mineral composition. The total vitamin C was positively correlated to K and negatively correlated to chlorophylls, N, P, Mg, Ca, S, and B (p < 0.01). These relationships can be applied in future vitamin C biofortification research across different microgreens. In conclusion, vitamin C was increased up to 222% by supplemental ascorbic acid without being detrimental to plant health and mineral composition.

Prospects of microgreens as budding living functional food: Breeding and biofortification through OMICS and other approaches for nutritional security

Nutrient deficiency has resulted in impaired growth and development of the population globally. Microgreens are considered immature greens (required light for photosynthesis and growing medium) and developed from the seeds of vegetables, legumes, herbs, and cereals. These are considered "living superfood/functional food" due to the presence of chlorophyll, beta carotene, lutein, and minerals like magnesium (Mg), Potassium (K), Phosphorus (P), and Calcium (Ca). Microgreens are rich at the nutritional level and contain several phytoactive compounds (carotenoids, phenols, glucosinolates, polysterols) that are helpful for human health on Earth and in space due to their anti-microbial, anti-inflammatory, antioxidant, and anti-carcinogenic properties. Microgreens can be used as plant-based nutritive vegetarian foods that will be fruitful as a nourishing constituent in the food industryfor garnish purposes, complement flavor, texture, and color to salads, soups, flat-breads, pizzas, and sandwiches (substitute to lettuce in tacos, sandwich, burger). Good handling practices may enhance microgreens'stability, storage, and shelf-life under appropriate conditions, including light, temperature, nutrients, humidity, and substrate. Moreover, the substrate may be a nutritive liquid solution (hydroponic system) or solid medium (coco peat, coconut fiber, coir dust and husks, sand, vermicompost, sugarcane filter cake, etc.) based on a variety of microgreens. However integrated multiomics approaches alongwith nutriomics and foodomics may be explored and utilized to identify and breed most potential microgreen genotypes, biofortify including increasing the nutritional content (macro-elements:K, Ca and Mg; oligo-elements: Fe and Zn and antioxidant activity) and microgreens related other traits viz., fast growth, good nutritional values, high germination percentage, and appropriate shelf-life through the implementation of integrated approaches includes genomics, transcriptomics, sequencing-based approaches, molecular breeding, machine learning, nanoparticles, and seed priming strategiesetc.

Agronomic biofortification of food crops: An emerging opportunity for global food and nutritional security

Fortification of food with mineral micronutrients and micronutrient supplementation occupied the center stage during the two-year-long Corona Pandemic, highlighting the urgent need to focus on micronutrition. Focus has also been intensified on the biofortification (natural assimilation) of mineral micronutrients into food crops using various techniques like agronomic, genetic, or transgenic. Agronomic biofortification is a time-tested method and has been found useful in the fortification of several nutrients in several crops, yet the nutrient use and uptake efficiency of crops has been noted to vary due to different growing conditions like soil type, crop management, fertilizer type, etc. Agronomic biofortification can be an important tool in achieving nutritional security and its importance has recently increased because of climate change related issues, and pandemics such as COVID-19. The introduction of high specialty fertilizers like nano-fertilizers, chelated fertilizers, and water-soluble fertilizers that have high nutrient uptake efficiency and better nutrient translocation to the consumable parts of a crop plant has further improved the effectiveness of agronomic biofortification. Several new agronomic biofortification techniques like nutripriming, foliar application, soilless activation, and mechanized application techniques have further increased the relevance of agronomic biofortification. These new technological advances, along with an increased realization of mineral micronutrient nutrition have reinforced the relevance of agronomic biofortification for global food and nutritional security. The review highlights the advances made in the field of agronomic biofortification via the improved new fertilizer forms, and the emerging techniques that achieve better micronutrient use efficiency of crop plants.

The Integral Boosting Effect of Selenium on the Secondary Metabolism of Higher Plants

Selenium is a micronutrient with a wide range of functions in animals, including humans, and in microorganisms such as microalgae. However, its role in plant metabolism remains ambiguous. Recent studies of Se supplementation showed that not only does it increase the content of the element itself, but also affects the accumulation of secondary metabolites in plants. The purpose of this review is to analyze and summarize the available data on the place of selenium in the secondary metabolism of plants and its effect on the accumulation of some plant metabolites (S- and N-containing secondary metabolites, terpenes, and phenolic compounds). In addition, possible molecular mechanisms and metabolic pathways underlying these effects are discussed. It should be noted that available data on the effect of Se on the accumulation of secondary metabolites are inconsistent and contradictory. According to some studies, selenium has a positive effect on the accumulation of certain metabolites, while other similar studies show a negative effect or no effect at all. The following aspects were identified as possible ways of regulating plant secondary metabolism by Se-supplementation: changes occurring in primary S/N metabolism, hormonal regulation, redox metabolism, as well as at the transcriptomic level of secondary metabolite biosynthesis. In all likelihood, the confusion in the results can be explained by other, more complex regulatory mechanisms in which selenium is involved and which affect the production of metabolites. Further study on the involvement of various forms of selenium in metabolic and signaling pathways is crucial for a deeper understanding of its role in growth, development, and health of plants, as well as the regulatory mechanisms behind them.

Nutritive and Phytochemical Composition of Aromatic Microgreen Herbs and Spices Belonging to the Apiaceae Family

Microgreens represent a new generation of food products, commonly used to garnish and embellish culinary dishes, and recently associated with an increasing interest in their nutraceutical and phytochemical profiles. Four Apiaceae species: Pimpinella anisum L. (anise), Anthriscus cerefolium L. (chervil), Carum carvi L. (caraway), and Anethum graveolens L. (dill) were assessed for fresh yield, macro- and microminerals, total chlorophylls, total ascorbic acid, carotenoids, polyphenols, and their antioxidant activity. Anise was the species yielding the most (2.53 kg m^-2) and having the highest lutein content (18.4 µg g^-1 dry weight (DW)). Chervil and dill were characterized by the highest total ascorbic acid content (~151 mg AA g^-1 fresh weight (FW)). The phenolic profile highlighted the presence of five flavonoid derivatives and 12 phenolic acid derivatives, with quinic acid derivatives being the most abundant phenols in the species tested. In addition, anise, caraway, and dill proved to be considerably rich in total polyphenols (~11056 μg g^-1 DW). Caraway and dill were characterized by the highest antioxidant activity measured by the DPPH and ABTS methods, whereas the FRAP method revealed caraway as having the highest antioxidant activity. Such results highlight the potential of Apiaceae species as an alternative to other families which are commonly used for microgreens production.

Zinc biofortification of hydroponically grown basil: Stress physiological responses and impact on antioxidant secondary metabolites of genotypic variants

Ocimum basilicum L. is an aromatic plant rich in bioactive metabolites beneficial to human health. The agronomic biofortification of basil with Zn could provide a practical and sustainable solution to address Zn deficiency in humans. Our research appraised the effects of biofortification implemented through nutrient solutions of different Zn concentration (12.5, 25.0, 37.5, and 50 µM) on the yield, physiological indices (net CO₂ assimilation rate, transpiration, stomatal conductance, and chlorophyll fluorescence), quality, and Zn concentration of basil cultivars 'Aroma 2' and 'Eleonora' grown in a floating raft system. The ABTS, DPPH, and FRAP antioxidant activities were determined by UV-VIS spectrophotometry, the concentrations of phenolic acids by mass spectrometry using a Q Extractive Orbitrap LC-MS/MS, and tissue Zn concentration by inductively coupled plasma mass spectrometry. Although increasing the concentration of Zn in the nutrient solution significantly reduced the yield, this reduction was less evident in 'Aroma 2'. However, regardless of cultivar, the use of the maximum dose of Zn (50 µM) increased the concentration of carotenoids, polyphenols, and antioxidant activity on average by 19.76, 14.57, and 33.72%, respectively, compared to the Control. The significant positive correlation between Zn in the nutrient solution and Zn in plant tissues underscores the suitability of basil for soilless biofortification programs.

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.

Sprouts and Microgreens-Novel Food Sources for Healthy Diets

With the growing interest of society in healthy eating, the interest in fresh, ready-to-eat, functional food, such as microscale vegetables (sprouted seeds and microgreens), has been on the rise in recent years globally. This review briefly describes the crops commonly used for microscale vegetable production, highlights Brassica vegetables because of their health-promoting secondary metabolites (polyphenols, glucosinolates), and looks at consumer acceptance of sprouts and microgreens. Apart from the main crops used for microscale vegetable production, landraces, wild food plants, and crops' wild relatives often have high phytonutrient density and exciting flavors and tastes, thus providing the scope to widen the range of crops and species used for this purpose. Moreover, the nutritional value and content of phytochemicals often vary with plant growth and development within the same crop. Sprouted seeds and microgreens are often more nutrient-dense than ungerminated seeds or mature vegetables. This review also describes the environmental and priming factors that may impact the nutritional value and content of phytochemicals of microscale vegetables. These factors include the growth environment, growing substrates, imposed environmental stresses, seed priming and biostimulants, biofortification, and the effect of light in controlled environments. This review also touches on microgreen market trends. Due to their short growth cycle, nutrient-dense sprouts and microgreens can be produced with minimal input; without pesticides, they can even be home-grown and harvested as needed, hence having low environmental impacts and a broad acceptance among health-conscious consumers.

Can Light Spectrum Composition Increase Growth and Nutritional Quality of Linum usitatissimum L. Sprouts and Microgreens?

Flaxseed could be suitable for obtaining high-quality sprouts and microgreens thanks to high amounts of nutrients and antioxidant, antidiabetic, and anticancer compound content in its seeds. Recent studies highlighted that seedling growth, nutritional compound, and secondary metabolite content can be strongly managed by regulation of the light spectrum used during germination. The present study intended to shed light on flaxseed as emerging and novel species for sprouts and microgreens and to evaluate the effect of light, with different spectrum compositions (100% blue, 100% red, 100% green, and red:green:blue—1:1:1) on the performance of flax microgreens and sprouts grown indoors under controlled conditions. Microgreens showed, compared to sprouts, a higher chlorophyll (+62.6%), carotenoid (+24.4%), and phenol content (+37.8%), antioxidant capacity (+25.1%) and a lower dry matter content (−30.7%). Besides, microgreens treated with 100% blue light were characterized by the highest content of flavonoids (2.48 mg CAE g−1 FW), total phenols (3.76 mg GAE g−1 FW), chlorogenic acid (1.10 mg g−1 FW), and antioxidant capacity (8.06 µmol TEAC g−1 FW). The paper demonstrates the feasibility of obtaining flax sprouts and microgreens indoors with a considerable antioxidant capacity and health-promoting compounds by modulating the light spectrum.

Effect of Selenium Application and Growth Stage at Harvest on Hydrophilic and Lipophilic Antioxidants in Lamb's Lettuce (Valerianella locusta L. Laterr.)

Lamb's lettuce (Valerianella locusta L. Laterr.) is a leafy green vegetable that is rich in various biological active compounds and is widely used in ready-to-eat salads. The cultivation conditions and growth stage could affect the secondary metabolism in plants and thereby modify their food value. In the present study, the effect of selenium (Se) application in various concentrations (5.0, 10.0, and 20.0 µM) on the contents of Se, phenolic compounds, vitamin C, carotenoids, chlorophylls, and antioxidant activity of hydrophilic and lipophilic extracts of lamb's lettuce harvested at three growth stages (38, 52, and 66 days after sowing (DAS)) was studied. Se application significantly increased the Se concentration in the shoots (up to 124.4 μg g^-1 dry weight), as well as the contents of chlorogenic acid, total flavonoids, total phenolics, ascorbic acid, chlorophyll b, and the antioxidant activity of hydrophilic and lipophilic extracts. A higher content of phenolic compounds and higher antioxidant activity of hydrophilic extracts was observed at the first growth stage (38 DAS). On the contrary, higher contents of lipophilic compounds (chlorophyll a, chlorophyll b, lutein, β-carotene) and higher antioxidant activity of lipophilic extracts were found for shoots harvested at later stages (52 and 66 DAS).

Overview of Multiple Applications of Basil Species and Cultivars and the Effects of Production Environmental Parameters on Yields and Secondary Metabolites in Hydroponic Systems

Basil (Ocimum basilicum L.), including other species and cultivars, is an excellent source of nutritional compounds, the accumulation of which can be stimulated by exogenous factors (environmental and nutritional conditions). Although best practices are relatively established for mature basil plants, microgreens production requires further research to optimize quality and quantity. The study objectives are (i) to provide an overview of the many uses of basil, (ii) collate and present common hydroponic systems available in the market, (iii) review effects of key production environment parameters on basil yields in hydroponic systems, and (iv) summarize the effects of the growth environments on yield quantity and quality of basil microgreens. The paper analyzes in detail key production parameters of basil microgreens in hydroponic systems, such as temperature, humidity, pH, electrical conductivity, dissolved oxygen, carbon dioxide, nutrient solutions, and the influence of light (quantity, quality, and photoperiods). The collated literature review has shown that basil, grown hydroponically, can tolerate high variations of environmental parameters: pH 5.1–8.5, temperature 15–24 °C, relative humidity 60–70%, electrical conductivity up to 1.2 mS cm−1, depending on the developmental stage, dissolved oxygen at 4 mg L−1 (optimally 6.5 mg L−1), and light intensity between 200 and 400 μmol m−2 s−1. The study has synthesized an overview of different production parameters to provide guidance on the optimization of environmental conditions to ensure the quantity and quality production of basil microgreens. Improving the quality of basil microgreens can ideally spur continued gastronomic interest in microgreens in general, which will encourage more entrepreneurs to grow basil and other microgreens. Hence, the study findings are a great resource to learn about the effects of different environments on basil microgreen production. This information can inform research for successful production of different species and cultivars of basil microgreens, and establishing testing protocols to improve the quantity and quality of the harvest.

Biofortification of Sodium Selenate Improves Dietary Mineral Contents and Antioxidant Capacity of Culinary Herb Microgreens

Selenium biofortification of plants has been suggested as a method of enhancing dietary selenium intake to prevent deficiency and chronic disease in humans, while avoiding toxic levels of intake. Popular herbs such as basil (Ocimum basilicum L.), cilantro (Coriandrum sativum L.), and scallions (Allium fistulosum L.) present an opportunity for biofortification as these plants are used for added flavors to meals and are available as microgreens, young plants with increasing popularity in the consumer marketplace. In this study, basil, cilantro, and scallion microgreens were biofortified with sodium selenate under hydroponic conditions at various selenium concentrations to investigate the effects on yield, selenium content, other mineral contents (i.e., sodium, potassium, calcium, magnesium, phosphorus, copper, zinc, iron, manganese, sulfur, and boron), total phenol content, and antioxidant capacity [oxygen radical absorbance capacity (ORAC)]. The results showed that the selenium content increased significantly at all concentrations, with scallions demonstrating the largest increase. The effects on other minerals varied among herb species. Antioxidant capacity and total phenol content increased in all herbs at the highest selenium treatments, but basil and scallions demonstrated a decreased crop yield. Overall, these biofortified culinary herb microgreens are an ideal functional food for enhancing selenium, other dietary minerals, and antioxidants to benefit human health.

Productive and Morphometric Traits, Mineral Composition and Secondary Metabolome Components of Borage and Purslane as Underutilized Species for Microgreens Production

Neglected and underutilized species (NUS) offer largely unexplored opportunities for providing nutritious plant food, while making agro-ecosystems more diverse and resilient to climate change. The aim of this work was to explore the potential of two typical Mediterranean underutilized species, purslane and borage, as novel vegetable product (microgreens). Micro-scale production of edible plants is spreading due to the simplicity of their management, rapid cycle, harvest index, and phytochemical value of the edible product. Microgreens, therefore, represent an opportunity to link NUS, nutrition, and agricultural and dietary diversification. By analyzing yield, antioxidants activities, mineral composition, and main phenolic acids and flavonoids, our work indicated that the two species provide interesting results when compared with those reported for crops and horticultural species. Specifically, purslane should be considered highly nutritional due to the amount of phenolic compounds and ascorbic acid, and to potential good β-carotene bioavailability. Borage microgreens have a very high fresh yield and a more composite and balanced phenolic profile. In conclusion, our work provided evidence for implementing new ways to expand the NUS market-chains and for developing added-value food products.

Selenium Biofortification of Soybean Seeds Influences Physiological Responses of Seedlings to Osmotic Stress

Climate change poses a serious threat to agricultural production. Water deficit in agricultural soils is one of the consequences of climate change that has a negative impact on crop growth and yield. Selenium (Se) is known to be involved in plant defense against biotic and abiotic stress through metabolic, structural, and physiological activity in higher plants. The aim of this study was to investigate the physiological response of Se-biofortified soybean (Glycine max (L.) Merrill) seedlings under osmotic stress. For this research, we used biofortified soybean grain obtained after foliar Se biofortification in 2020. The experiment was conducted in a growth chamber with two cultivars (Lucija and Sonja) grown on filter paper in three replicates. The experiment was carried out with two watering treatments: distilled water (PEG-0) and 2.5% polyethylene glycol 6000 (PEG-2.5) on Se-biofortified seeds (Se) and nonbiofortified seeds (wSe). Contents of lipid peroxidation product (LP), free proline (PRO), total phenolic content (TP), ferric reducing antioxidant power (FRAP), and ascorbic acid (AA) were analyzed in 7-days-old seedlings. Significant differences were detected in the Se content of soybean grains between the two cultivars. A milder reaction to PEG-2.5 was observed in cultivar Lucija in both Se and wSe treatments, which might represent the mitigating effects of Se on osmotic stress in this cultivar. Contrarily, in cultivar Sonja, Se adversely affected all analyzed traits in the PEG-2.5 treatment. Ultimately, Se is a pro-oxidant in Sonja, whereas it represents an anti-oxidant in Lucija. In conclusion, different soybean cultivars show contrasting physiological reactions to both osmotic stress and Se. However, the activation of antioxidant pathways in Sonja can also be interpreted as added value in soybean seedlings as a functional food.

Joint Biofortification of Plants with Selenium and Iodine: New Field of Discoveries

The essentiality of selenium (Se) and iodine (I) to human beings and the widespread areas of selenium and iodine deficiency determine the high significance of functional food production with high levels of these elements. In this respect, joint biofortification of agricultural crops with Se and I is especially attractive. Nevertheless, in practice this topic has raised many problems connected with the possible utilization of many Se and I chemical forms, different doses and biofortification methods, and the existence of wide species and varietal differences. The limited reports relevant to this subject and the multiplicity of unsolved questions urge the need for an adequate evaluation of the results obtained up-to-date, useful for developing further future investigations. The present review discusses the outcome of joint plant Se-I biofortification, as well as factors affecting Se and I accumulation in plants, paying special attention to unsolved issues. A particular focus has been given to the prospects of herb sprouts production enriched with Se and I, as well as the interactions between the latter microelements and arbuscular-mycorrhizal fungi (AMF).

The role of emerging micro-scale vegetables in human diet and health benefits-an updated review based on microgreens

Increasing public concern about health has prompted humans to find new sources of food. Microgreens are young and immature plants that have been recently introduced as a new category of vegetables, adapting their production at the micro-scale. In this paper, the chemical compositions including micro-nutrients and some typical phytochemicals of microgreens are summarized. Their edible safety and potential health benefits are also reviewed. Microgreens play an increasingly vital role in health-promoting diets. They are considered good sources of nutritional and bioactive compounds, and show potential in the prevention of malnutrition and chronic diseases. Some strategies in the pre- or post-harvest stages of microgreens can be further applied to obtain better nutritional, functional, and sensorial quality with freshness and extended shelf life. This review provides valuable nutrient data and health information for microgreens, laying a theoretical foundation for people to consume microgreens more wisely, and providing great value for the development of functional products with microgreens.

The Use of a Nutrient Quality Score is Effective to Assess the Overall Nutritional Value of Three Brassica Microgreens

Microgreens have immense potential for improving dietary patterns, but little information is available regarding their overall nutritional value. We evaluated the nutritional traits of three hydroponically grown Brassica microgreens by using a Nutrient Quality Score. Micro cauliflower, micro broccoli and micro broccoli raab were grown using nutrient solutions with three different NH₄:NO₃ molar ratios (5:95, 15:85, and 25:75). Protein, dietary fiber, β-carotene, α-tocopherol and mineral elements (Ca, K, Mg, Fe, Zn, Cu, Mn, and Na) were analyzed. We developed the Nutrient Quality Score (NQS 11.1) on the basis of 11 desirable nutrients and 1 nutrient (sodium) to be limited. All Brassica microgreens are an excellent source of Vitamins A and E (more than 20% of the daily reference value—DRV), as well as a good source of calcium and manganese (10–19% of the DRV). Micro cauliflower showed a NQS 11.1 at 47% higher than micro broccoli raab and micro broccoli. Using NH₄:NO₃ 25:75 molar ratio, the average score was 27% higher than other molar ratios. In all cases, the microgreens in the present study showed a higher NQS 11.1 than their mature counterpart (on the basis of data from the United States Department of Agriculture), highlighting that the score of micro cauliflower was about six-fold higher than mature cauliflower. In conclusion, the NQS 11.1 was useful for assessing the overall nutritional quality of the three Brassica microgreens, instead of simply quantifying nutrient content, in order to compare a single nutrient among different genotypes. Furthermore, the results highlight that the micro broccoli raab, micro broccoli and micro cauliflower in this study can be considered nutrient-rich vegetables that are able to improve dietary patterns more effectively than their mature counterparts.

Sensory Attributes and Consumer Acceptability of 12 Microgreens Species

Microgreens are gaining increasing recognition among consumers, acclaimed for their freshness and health promoting properties associated with densely fortified secondary metabolites. These immature greens enhance human diet and enrich it with sharp colors and flavors. While numerous species are being tested for agronomic and nutritional suitability, consumer acceptance of appearance, texture, and flavor is critical for the microgreens’ marketplace success. This study investigates whether sensory attributes and visual appearance affect consumer preference for microgreens and their willingness to consume them. By means of a consumer test, the sensory attributes of 12 microgreens species were evaluated, wherein a partial least squares structural equation model was developed to link sensorial attributes to willingness to eat the product. The results showed that although visual appearance of the microgreens was largely appreciated, consumer acceptance overall was mainly determined by flavor and texture. In particular, the lower the astringency, sourness, and bitterness, the higher the consumer acceptability of microgreens. Among the 12 examined species, mibuna and cress scored the lowest acceptance by consumers, while Swiss chard and coriander were the most appreciated, being therefore good candidates to be introduced in Western country markets. In addition, both Swiss chard and coriander have been identified by previous literature as good dietary source of phenolic antioxidants.

Yield and Quality Characteristics of Brassica Microgreens as Affected by the NH4:NO3 Molar Ratio and Strength of the Nutrient Solution

Microgreens are gaining more and more interest, but little information is available on the effects of the chemical composition of the nutrient solution on the microgreen yield. In this study, three Brassica genotypes (B. oleracea var. italica, B. oleracea var. botrytis, and Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort) were fertigated with three modified strength Hoagland nutrient solutions (1/2, 1/4, and 1/8 strength) or with three modified half-strength Hoagland nutrient solutions with three different NH₄:NO₃ molar ratios (5:95, 15:85, and 25:75). Microgreen yields and content of inorganic ions, dietary fiber, proteins, α-tocopherol, and β-carotene were evaluated. Micro cauliflower showed the highest yield, as well as a higher content of mineral elements and α-tocopherol (10.4 mg 100 g^-1 fresh weight (FW)) than other genotypes. The use of nutrient solution at half strength gave both a high yield (0.23 g cm^-2) and a desirable seedling height. By changing the NH₄:NO₃ molar ratio in the nutrient solution, no differences were found on yield and growing parameters, although the highest β-carotene content (6.3 mg 100 g^-1 FW) was found by using a NH₄:NO₃ molar ratio of 25:75. The lowest nitrate content (on average 6.8 g 100 g^-1 dry weight) was found in micro broccoli and micro broccoli raab by using a nutrient solution with NH₄:NO₃ molar ratios of 25:75 and 5:95, respectively. Micro cauliflower fertigated with a NH₄:NO₃ molar ratio of 25:75 showed the highest dry matter (9.8 g 100 g^-1 FW) and protein content (4.2 g 100 g^-1 FW).

Selenium biofortification in the 21st century: status and challenges for healthy human nutrition

BACKGROUND

Selenium (Se) is an essential element for mammals and its deficiency in the diet is a global problem. Plants accumulate Se and thus represent a major source of Se to consumers. Agronomic biofortification intends to enrich crops with Se in order to secure its adequate supply by people.

SCOPE

The goal of this review is to report the present knowledge of the distribution and processes of Se in soil and at the plant-soil interface, and of Se behaviour inside the plant in terms of biofortification. It aims to unravel the Se metabolic pathways that affect the nutritional value of edible plant products, various Se biofortification strategies in challenging environments, as well as the impact of Se-enriched food on human health.

CONCLUSIONS

Agronomic biofortification and breeding are prevalent strategies for battling Se deficiency. Future research addresses nanosized Se biofortification, crop enrichment with multiple micronutrients, microbial-integrated agronomic biofortification, and optimization of Se biofortification in adverse conditions. Biofortified food of superior nutritional quality may be created, enriched with healthy Se-compounds, as well as several other valuable phytochemicals. Whether such a food source might be used as nutritional intervention for recently emerged coronavirus infections is a relevant question that deserves investigation.