Main Se Species Research Articles

Toxicokinetics of selenate in earthworm sub-tissues and potential bio-accessibility assessment of earthworm-derived selenium

Selenium (Se) pollution is mainly caused by anthropogenic activities, and the resulting biosecurity concerns have garnered significant attention in recent years. Using one-compartmental toxicokinetic (TK) modelling, this study explored the kinetic absorption, sub-tissue distribution, and elimination processes of the main Se species (selenate, Se(VI)) in the cultivated aerobic soil of the earthworm Eisenia fetida. The bio-accessibility of earthworm-derived Se was assessed using an in vitro simulated gastrointestinal digestion test to evaluate its potential trophic risk. The results demonstrated that Se accumulated in the pre-clitellum (PC) and total tissues (TT) of earthworms in a time- and dose-dependent manner. The highest Se levels in the PC, post-clitellum (PoC), and TT were 70.54, 57.93, and 64.26 mg/kg during the uptake phase, respectively. The kinetic Se contents in the earthworms PC and TT were consistent with the TK model but not with PoC. The earthworm TT exhibited a faster uptake (Kus = 0.83–1.02 mg/kg/day) and elimination rate of Se (Kee = 0.044–0.049 mg/kg/day), as well as a shorter half-life time (LT1/2 = 15.88–14.22 days) than PC at low soil Se levels (≤5 mg/kg). Conversely, the opposite trend was observed with higher Se concentrations (10 and 20 mg/kg). These results are likely attributable to the tissue specificity and concentration of the toxicant. Earthworms PC and TT exhibited a higher kinetic Se accumulation factor (BAFk) than steady-state BAF (BAFss), with values ranging from 8 to 24 and 3–13, respectively. Furthermore, the bio-accessibility of earthworm-derived Se to poultry ranged from 66.25 % to 84.35 %. As earthworms are at the bottom of the terrestrial food chain, the high bio-accessibility of earthworm-derived Se poses a potential risk to predators. This study offers data support and a theoretical foundation for understanding the biological footprint of soil Se and its toxicological impacts and ecological hazards.

Selenium contents, speciation and bioaccessibility of Se-enriched rice grains from Chinese markets

Diet intake accounts for >90% of selenium (Se) exposure in humans, with rice being the main source of Se intake for >60% of the Chinese population. In this study, 48 rice grain samples labeled Se-enriched were obtained from 22 major rice producing areas in China through online sources. Their total Se contents, Se speciation, and Se bioaccessibility were evaluated to provide a holistic view of Se-enriched rice in the market. The total Se contents were 0.006–0.951 ​μg ​g−1 (average 0.249 ​μg ​g−1), which showed great regional variations, with 73% of the samples satisfying the Se-enriched standard based on GB/T22499-2008 (0.04–0.30 ​mg ​kg−1). Over 80% of Se in the rice samples was organic Se species including selenomethionine, selenocysteine and methylselenocysteine, with selenomethionine being the main Se species, accounting for 61–98%. Based on a modified physiologically-based extraction test (MPBET), the Se bioaccessibility in 33 selected samples was 8.05–49.6% (28.6%) in the gastric phase and 18.1–117% (82.5%) in the intestinal phase. Further, Se bioaccessibility was positively correlated with organic Se (r ​= ​0.89–0.93), but not with inorganic Se (selenite and selenate), suggesting that Se bioaccessibility depended on organic Se in these rice grains. The data call for re-evaluation of Se-enriched rice in the market. Further, the potential risk of long-term consumption of Se-enriched rice in the market towards human health should be studied.

Sulfur levels regulate the absorption and utilization of selenite in rapeseed (Brassica napus)

Selenium (Se) is a necessary trace element that contributes to the health of humans and animals alike. Humans rely on the consumption of Se-rich plants to achieve adequate levels of the nutrient, but many crop-growing regions are unable to keep up with demand through conventional agriculture alone. Hydroponic cultivation with inorganic Se sources such as selenate or selenite represents a valid opportunity for biofortification in plants. This method is largely free from dependence on local Se resources, and the appropriate optimizations of hydroponic ingredients have previously demonstrated improved plant Se. However, effective strategies to improve the absorption and utilization efficiency of selenite at physiological levels remain scarce. In this study, we manipulated sulfate levels in a selenite-containing hydroponic solution and found that a decreased supply was able to elevate Se contents more than 6-fold in the shoots of rapeseed seedlings, but only had a slight effect in the roots. Additionally, this low sulfur environment increased the root-to-shoot Se translocation efficiency by more than 6 times. Our Se speciation analysis showed that a large proportion of the root-absorbed selenite was transformed into organic forms under a normal sulfate supply, and that selenate and SeMeCys represent the main Se species involved in root-to-shoot translocation. A reduction in sulfate supply was also found to induce the upregulation of genes related to selenate distribution and a key rate-limiting step for organic Se biosynthesis. These findings are consistent with the dramatically enhanced accumulation of SeMet and selenate in both roots and shoots. Taken together, our results demonstrate that the regulation of sulfur levels has a great potential for the improvement of the Se enrichment efficiency in economically valuable aboveground organs of selenite-treated plants.

Spatial Metallomics Reveals Preferable Accumulation of Methylated Selenium in a Single Seed of the HyperaccumulatorCardamine violifolia

Cardamine violifolia is a Se hyperaccumulator found in Enshi, China. In this study, spatial metallomics was applied to visualize the distribution and speciation of Se in a single seed of C. violifolia. It was found that Se reached 1729.89 ± 28.14 mg/kg and the main Se species were SeCys and SeMet in bulk seeds. Further in situ study on a single seed found that the methylated Se species located mostly in the episperm. This is the first visualized evidence of the in situ distribution of methylated Se species in the seeds of C. violifolia. In all, spatial metallomics finds a preferable accumulation of methylated Se species in the seed coat, which deepens the understanding of the tolerance of Se by C. violifolia. The protocol applied in this study may also be used for the understanding of the tolerance of heavy metals/metalloids in other hyperaccumulators.

The Influence of Thiol Addition on Selenium Stability and Antioxidant Activity of Beetroot Juice

Determination of selenium species in food samples causes problems due to their possible oxidation and degradation. In this study, the stability of selenium compounds present in beetroot juices after addition of recommended thiols, such as ditiotreitol (DDT) or β-mercaptoethanol (βME), was evaluated. More total selenium was found in homemade freshly squeezed beetroot juice than in that sold as an organic juice. Furthermore, Se(IV) and selenomethionine oxide (SeMetO) were the main Se species found in both juices. During storage at different temperatures, the concentrations of selenomethionine (SeMet) and Se-methylselenocysteine (MetSeCys) decreased, while Se(IV) and SeMetO contents increased. The addition of DDT or βME, regardless their concentration, did not increase the concentration of SeMet at the expense of SeMetO decrease, as it was expected based on the literature data. Moreover, the used thiols affected the quantification of other selenium species, particularly Se(IV). The purchased organic beetroot juice showed higher ability to scavenge free radicals when it was stored at 4 °C.

Soil and foliar selenium application: Impact on accumulation, speciation, and bioaccessibility of selenium in wheat (Triticum aestivum L.).

A comprehensive study in selenium (Se) biofortification of staple food is vital for the prevention of Se-deficiency-related diseases in human beings. Thus, the roles of exogenous Se species, application methods and rates, and wheat growth stages were investigated on Se accumulation in different parts of wheat plant, and on Se speciation and bioaccessibility in whole wheat and white all-purpose flours. Soil Se application at 2 mg kg–1 increased grains yield by 6% compared to control (no Se), while no significant effects on yield were observed with foliar Se treatments. Foliar and soil Se application of either selenate or selenite significantly increased the Se content in different parts of wheat, while selenate had higher bioavailability than selenite in the soil. Regardless of Se application methods, the Se content of the first node was always higher than the first internode. Selenomethionine (SeMet; 87–96%) and selenocystine (SeCys2; 4–13%) were the main Se species identified in grains of wheat. The percentage of SeMet increased by 6% in soil with applied selenite and selenate treatments at 0.5 mg kg–1 and decreased by 12% compared with soil applied selenite and selenate at 2 mg kg–1, respectively. In addition, flour processing resulted in losses of Se; the losses were 12–68% in white all-purpose flour compared with whole wheat flour. The Se bioaccessibility in whole wheat and white all-purpose flours for all Se treatments ranged from 6 to 38%. In summary, foliar application of 5 mg L–1 Se(IV) produced wheat grains that when grounds into whole wheat flour, was the most efficient strategy in producing Se-biofortified wheat. This study provides an important reference for the future development of high-quality and efficient Se-enriched wheat and wheat flour processing.

Effect of foliar spraying of organic and inorganic selenium fertilizers during different growth stages on selenium accumulation and speciation in rice

AimsMost crops are supplemented with selenium (Se) through the exogenous addition of inorganic Se fertilizer. There is a lack of in-depth research on organic Se fertilizers. Meanwhile, the dosage range between human Se deficiency and Se toxicity is narrow, so the Se content of agricultural products needs to be controlled within a reasonable interval.MethodsSe accumulation and speciation in rice were analyzed and compared during three different growth stages (late tillering stage, initiate heading stage, and full heading stage) using three Se fertilizers: selenite, fermented Se, and potassium selenocyanoacetate (Se-AAF) via the foliar application.ResultsThe Se content in rice sprayed with organic Se fertilizer was controlled in the relatively safe range and met the human Se supplement requirement compared to the sprayed sodium selenite, which was too high of a dose. The percentage of organic Se and protein Se in brown rice was found to be similar in all three Se fertilizers. The highest organic Se content of 91.57% was found in the grain of rice at the full heading stage by spraying Se-AAF. The main Se species in the grain was selenomethionine (SeMet), which reached 80% of the total Se. Se-methyl selenocysteine(SeMeCys) was found only in Se-AAF. The grain quality showed that all three Se fertilizers increased the consistency of gelatinization.ConclusionsAppropriately delaying the spraying time and selecting organic Se fertilizer as the Se source can help to produce green and safe selenium-rich rice.

Effect of protease XXIII on selenium species interconversion during their extraction from biological samples

Protease XIV is the most common used agent for selenium species extraction from biological samples. In this work, the interconversion of selenocystine during extraction with Tris−HCl buffer containing protease XIV was demonstrated. The 29 % of selenocystine was converted to species with retention time corresponding to Se-methyl-selenocysteine. In addition, selenomethionine, selenoethionine, and Se-methyl-selenocysteine were oxidized to their oxo-analogues when 0.1 % Triton X-100 or 0.1 % sodium dodecyl sulphate was used for improvement of extraction efficiency. The interconversion of these species was suppressed by using a protease XXIII, which application for the extraction of selenium species is described here for the first time. The method for speciation analysis of nine Se species (selenate, selenite, selenomethionine, selenocystine, Se-methyl-selenocysteine, selenoethionine, trimethylselenonium, methylselenocysteine oxide, and selenomethionine Se-oxide) using extraction with protease XXIII was developed and validated (limits of quantitation 0.21–0.70 μg/L Se, linearity up to 1000 μg/L Se, spike recovery 92.3–110.1 %). It has also been shown that the extraction efficiency of protease XXIII (average 53 %) is only slightly lower in comparison to protease XIV (average 65 %). The main Se species in biological samples, selenomethionine, selenocystine, and Se-methyl-selenocysteine, were stable in extract for three days at room temperature.

Comparative study of the effects of selenium yeast and sodium selenite on selenium content and nutrient quality in broccoli florets (Brassica oleracea L. var. italica).

Approximately 0.5-1 billion people worldwide face the risk of selenium (Se) deficiency because of the low Se concentration in their diets. Broccoli can accumulate Se and comprises a source of daily Se supplement for humans. Se biofortification is an effective strategy for enhancing Se content in crops. In the present study, the effects of Se yeast and selenite application on the Se content and nutrient quality of broccoli were investigated. Broccoli growth was promoted by Se yeast but inhibited by selenite. The total Se content of broccoli florets remarkably increased with increasing exogenous Se fertilizer concentrations. The main Se species in broccoli florets were methyl-selenocysteine and selenomethionine, and their contents were significantly higher under Se yeast treatments than under selenite treatments. Se(VI) was detected only under selenite treatments. Se yeast and selenite had different influences on soluble sugar, soluble protein, vitamin C and free amino acid contents in broccoli florets. The total phenolic acid and glucosinolate contents were substantially increased by Se yeast and selenite, although the total flavonoid content was reduced by Se yeast. Tests on antioxidant enzyme activities revealed that several antioxidant enzymes (catalase, peroxidase, superoxide dismutase and glutathione peroxidase) responded to Se yeast and selenite treatments. Se yeast is preferred over selenite for maximizing Se uptake and nutrient accumulation in Se-rich broccoli cultivation. However, an extremely high Se content in broccoli florets cannot be directly consumed by humans, although they can be processed into Se supplements. © 2021 Society of Chemical Industry.

Co-application of Se and a biostimulant at different wheat growth stages: Influence on grain development

An appropriate selenium intake can be beneficial for human health. Se-biofortified food in Se-deficient regions is becoming an increasingly common practice but there are still issues to be addressed regarding the observed Se-induced toxicity to the plant. In this respect, plant biostimulants are used to enhance nutrition efficiency, abiotic stress tolerance and crop quality. In this work, the efficacy of a plant biostimulant to counteract the Se-induced stress in wheat plants is experimentally assessed. The co-application of different Se-biofortification treatments and the biostimulant at different growth stages (tillering or heading stage) was investigated. The use of micro focused X-ray spectroscopy allows us to confirm organic Se species to be the main Se species found in wheat grain and that the proportion of organic Se species is only slightly affected by the Se application stage. Our study proves that the biostimulant had a key role in the enhancement of both the amount of grains produced per spike and their dry biomass without hindering Se enrichment process, neither diminishing the Se concentration nor massively disrupting the Se species present. This information will be useful to minimize both plant toxicity and economic cost towards a more effective and plant healthy selenium supplementation.

Influence of a plant biostimulant on the uptake, distribution and speciation of Se in Se-enriched wheat (Triticum aestivum L. cv. Pinzón)

Selenium (Se) can induce stress in plants. Our main purpose is to assess the effect of a biostimulant, based on hetero-polyoxometalates mixed with humic acids, on Se bio-fortified wheat plants. Secondly, to evaluate a possible modification of the Se species in the plant tissues and to investigate the response of phytohormones. Wheat plants were grown hydroponically and exposed to either selenite (Se(IV)), selenate (Se(VI)) or a mixture of both species (Se(MIX)) in the presence or absence of the biostimulant (foliar, FA; or root application, RA). Biomass, mineral nutrient concentration, phytohormones and Se speciation were investigated. The biostimulant FA did not modify the plant biomass but RA significantly increased the root biomass in all treatments as well as the shoot biomass of plants exposed to Se(VI) and Se(MIX) even when both modes of application caused a severe reduction of IAA levels in shoots. The biostimulant accelerated the translocation of Se from roots to shoots in the presence of Se(VI) and Se(MIX), and it only had a noticeable influence on the Se speciation in roots, but not significant in shoots. X-ray absorption spectroscopy allowed to identify organic Se as the main Se species formed in the shoots. The biostimulant has a mild effect on the Se speciation. The biostimulant has a remarkable influence on both the uptake and accumulation of certain mineral nutrients and the plant metabolism by increasing the biomass under Se exposure. This indicates the potential of this biostimulant that also will prevent the possible Se-induced plant stress.

Dynamics of Selenium uptake, speciation, and antioxidant response in rice at different panicle initiation stages

Selenium (Se) is an essential element in animals and humans, and its deficiency may cause conditions such as cardiac disease. The production of Se-enriched rice is one of the most important ways to supply Se in the human body, and thus, understanding of the mechanisms of Se-enriched rice is of great significance. A pot experiment was conducted to study the effects of Se addition on the growth, antioxidation, Se uptake and distribution, and Se speciation in three different stages of panicle initiation stage (i.e., pistil and stamen formation stage, pollen mother cell formation stage, pollen mother cell meiosis stage) and the maturity stage. The results showed that soil Se application significantly increased Se uptake in rice. Low rates of Se (<5 mg kg-1) application enhanced the plant growth and rice yield. Se speciation assays showed that SeCys and SeMet were the two main forms found in rice, of which SeMet accounted for 65.5%-100% in the ears and leaves, while SeCys accounted for 61.4%-75.6% in brown rice. SeMet was also the main Se-species found in different subcellular parts at the panicle initiation stage. However, inorganic Se was present in brown rice, mainly as Se(VI), when the soil Se addition exceeded 5 mg kg-1. Lower rates of Se (<5 mg kg-1) promoted the antioxidant capacity, while high levels of Se (≥5 mg kg-1) reduced the antioxidant capacity of rice. The results indicate that Se effects are dose dependent, and the suitable amount of soil Se application for Se-enriched rice production would be <5 mg kg-1.

Effects of Chinese Cooking Methods on the Content and Speciation of Selenium in Selenium Bio-Fortified Cereals and Soybeans.

Cereals and soybeans are the main food sources for the majority of Chinese. This study evaluated the effects of four common cooking methods including steaming, boiling, frying, and milking on selenium (Se) content and speciation in seven selenium bio-fortified cereals and soybeans samples. The Se concentrations in the selected samples ranged from 0.91 to 110.8 mg/kg and selenomethionine (SeMet) was detected to be the main Se species. Total Se loss was less than 8.1% during the processes of cooking except milking, while 49.1% of the total Se was lost in milking soybean for soy milk due to high level of Se in residuals. It was estimated that about 13.5, 24.0, 3.1, and 46.9% of SeMet were lost during the processes of steaming, boiling, frying, and milking, respectively. Meanwhile, selenocystine (SeCys2) and methylselenocysteine (SeMeCys) were lost completely from the boiled cereals. Hence, steaming and frying were recommended to cook Se-biofortified cereals in order to minimize the loss of Se.

Selenium uptake and Se compounds in Se-treated buckwheat

AbstractIn field experiments, tartary buckwheat and hybrid buckwheat were foliarly sprayed with an aqueous solution of sodium selenate (20 mg Se L-1). In treated plants, the selenium content was significantly higher than in controls, irrespective of the plant part and taxon of buckwheat. The highest average Se concentrations in hybrid and tartary buckwheat were found in seeds. The main Se species found in seeds was Semethionine. Selenium-sprayed plants had higher photochemical efficiency of photosystem II in both taxa and higher electron transport system activity in hybrid buckwheat, suggesting a positive effect of Se on physiological characteristics. Because of the concentration of Se in both buckwheat taxa and selenomethionine as the dominant species of Se, Se-enriched buckwheat is a potential source of dietary Se for animals and humans.

Bioaccessibility of selenium after human ingestion in relation to its chemical species and compartmentalization in maize.

Selenium is a micronutrient needed by all living organisms including humans, but often present in low concentration in food with possible deficiency. From another side, at higher concentrations in soils as observed in seleniferous regions of the world, and in function of its chemical species, Se can also induce (eco)toxicity. Root Se uptake was therefore studied in function of its initial form for maize (Zea mays L.), a plant widely cultivated for human and animal food over the world. Se phytotoxicity and compartmentalization were studied in different aerial plant tissues. For the first time, Se oral human bioaccessibility after ingestion was assessed for the main Se species (Se(IV) and Se(VI)) with the BARGE ex vivo test in maize seeds (consumed by humans), and in stems and leaves consumed by animals. Corn seedlings were cultivated in hydroponic conditions supplemented with 1mgL(-1) of selenium (Se(IV), Se(VI), Control) for 4months. Biomass, Se concentration, and bioaccessibility were measured on harvested plants. A reduction in plant biomass was observed under Se treatments compared to control, suggesting its phytotoxicity. This plant biomass reduction was higher for selenite species than selenate, and seed was the main affected compartment compared to control. Selenium compartmentalization study showed that for selenate species, a preferential accumulation was observed in leaves, whereas selenite translocation was very limited toward maize aerial parts, except in the seeds where selenite concentrations are generally high. Selenium oral bioaccessibility after ingestion fluctuated from 49 to 89% according to the considered plant tissue and Se species. Whatever the tissue, selenate appeared as the most human bioaccessible form. A potential Se toxicity was highlighted for people living in seleniferous regions, this risk being enhanced by the high Se bioaccessibility.

Preparation and characterization of a laboratory scale selenomethionine-enriched bread. Selenium bioaccessibility.

This study focuses on the preparation at lab scale of selenomethionine-enriched white and wholemeal bread. Selenium was supplemented either by adding selenite directly to the dough or by using lab-made selenium-enriched yeast. The best results were obtained when using fresh selenium-enriched yeast. The optimum incubation time for selenomethionine-enriched yeast preparation, while keeping formation of selenium byproducts to a minimum, was 96 h. Selenium content measured by isotope dilution analysis (IDA)-ICP-MS in Se-white and Se-wholemeal bread was 1.28 ± 0.02 μg g–1 and 1.16 ± 0.02 μg g–1 (expressed as mean ± SE, 3 replicates), respectively. HPLC postcolumn IDA-ICP-MS measurements revealed that selenomethionine was the main Se species found in Se-enriched bread, which accounted for ca. 80% of total selenium. In vitro gastrointestinal digestion assay provided selenium bioaccessibility values of 100 ± 3% and 40 ± 1% for white and wholemeal Se-enriched bread, respectively, being selenomethionine the main bioaccessible Se species in white bread, while in wholemeal bread this compound was undetectable.

Agronomic selenium biofortification in Triticum durum under Mediterranean conditions: From grain to cooked pasta

To improve the nutritional value of durum wheat and derived products, two foliar Se fertilisers (sodium selenate and selenite) were tested at four rates (0–10–20–40gha−1) in 2010/2011 and 2011/2012 in southwestern Spain. There was a strong and linear relationship between total Se or selenomethionine (Se-Met) accumulation in grain and Se dose for both fertilisers, although selenate was much more efficient. Se-Met was the main Se species (≈90%) of the total Se extracted from all materials. Milling caused a 27% loss of Se due to the removal of Se located in bran and germ. In the pasta making process and the cooking process the loss of Se, mainly as selenite, was about 7%. Durum wheat may be a good candidate to be included in Se biofortification programs under rainfed Mediterranean conditions, as foodstuffs derived from it could efficiently increase the Se content in the human diet.

Selenium compounds in selenium-enriched cabbage

For the study, cabbage (Brassica oleracea var. capitata L.) and red cabbage (Brassica oleracea var. capitata L. f. rubra) were treated with Na selenate. Cabbage was foliarly sprayed twice with 20 mg Se(VI) L–1, while red cabbage was fertilized twice with 0.5 mg Se(VI) L–1. Despite the high dose of Se, no toxic effects were observed on cabbage plants. The total Se concentration in cabbage leaves was 4.80 ± 0.25 μg Se g–1 (DM) and in red cabbage 0.96 ± 0.04 μg Se g–1 (DM). Soluble Se compounds were extracted from parts of cabbage with protease XIV, resulting in 49 % of soluble Se from roots, 59 % from leaves, and 65 % from stems. In red cabbage, the corresponding figures were 28 % of soluble Se in roots, 31 % in stems, and 43 % in leaves. Se species were determined in the enzymatic extracts using ion exchange high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). The main Se species found in all parts of cabbage and red cabbage was selenomethionine (SeMet), which in roots represented 94 and 55 % of the soluble Se content in cabbage and red cabbage, respectively. In stems and leaves of cabbage, SeMet represented only 23 % of the soluble Se content. In stems of red cabbage SeMet represented 80 % and in leaves 41 % of the soluble Se content. We observed that traces of Se(VI) were present in upper parts of both plants.

Selenium speciation in different organs of African catfish (Clarias gariepinus) enriched through a selenium-enriched garlic based diet

Speciation of Se in fish is needed to elucidate the metabolism of this element in living organisms in the marine environment. In this paper, selenium concentration and its species distribution in several organs and tissues (liver, gills, kidney, muscle and gastrointestinal tract) of African catfish fed with a selenium-enriched garlic based diet was studied. The intention of this paper is focused on both the investigation of selenium distribution in the soluble protein fraction and the detection of selenoaminoacids. Thus, two different procedures have been developed. In the first procedure, screening of selenium in proteins in the Tris-buffer soluble fraction of different tissues was carried out by size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS) and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) separation and electroblotting onto membranes. For the amino acid analysis, several sample treatments for Se-species extraction, based on enzymatic hydrolysis, were compared. The best results were obtained for incubation at controlled temperature. Application of several sample treatments in conjunction with different chromatographic techniques (reverse phase, anion exchange and ion exchange/size exclusion) was crucial to unambiguous Se-species identification. In Se-enriched African catfish a noticeable increase in the content of selenium in different organs was observed, except for the liver, where the Se level remained unaltered. The kidney was the Se-target organ in animals fed with enriched Se food. Selenomethionine (SeMet) was the main Se species identified in fillet extracts, whereas the presence of selenocysteine (SeCys) was detected in the liver and both SeMet and SeCys were present in the kidney.

Selenium biotransformation by Saccharomyces cerevisiae and Saccharomyces bayanus during white wine manufacture: Laboratory-scale experiments

The main purpose of this laboratory-scale study was to evaluate the transformation of inorganic selenium, as sodium selenite, when added to white grape juice as part of the fermentation process of white wine. The participation of yeast, added in the fermentation of the must, is necessary to convert inorganic selenium into organoseleno species. Two different yeasts, Saccharomyces cerevisiae and Saccharomyces bayanus were used for fermentation. The effects of different Se concentrations on cells and their viability during fermentation were evaluated. The alcoholic fermentation that produced wine was not affected by the presence of selenium, regardless of the type of Saccharomyces used. After 21 days of fermentation, the white wine and residual yeast were separated and analysed by ICP-MS and LC–ICP-MS for determination of total selenium and speciation. Selenomethionine was found to be the main Se-species in the selenised white wine. The results obtained are preliminary but they could be considered for future studies using both pilot and full-scale vinification processes.