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

BACKGROUND: As a potential selenium-enriched crop, it is of great significance to study the selenium application of Tartary buckwheat. Therefore, to study the effects of selenium application concentration, variety, selenium application period and method on the grain selenium content and yield of Tartary buckwheat, an orthogonal experimental design was used to carry out field experiments in the Jinzhong and Northwest Shanxi ecological regions at the same time. Heifeng 1 and Jinqiao 2 were applied at the branching stage and flowering stage in the Jinzhong, and Heifeng 1 and Jinqiao 6 were applied at the early flowering stage and peak flowering stage in the Northwest Shanxi with different concentrations of sodium selenite (0, 1.37, 2.74, 5.48, 8.22, 12.33, 18.495, 27.7425 g hm-2 ) by foliar spraying and soil application. RESULTS: The results showed that the selenium content in Tartary buckwheat grains was positively correlated with the selenium application concentration and increased with increasing selenium application concentration, while the yield of Tartary buckwheat first increased and then decreased with the selenium application concentration. The grain selenium content and yield of Tartary buckwheat were affected by the selenium application concentration, variety and application method. CONCLUSION: The most effective selenium biofortification program was spraying 2.32 g hm-2 sodium selenite on the leaves of Heifeng 1 at the early flowering stage in the Jinzhong. In the Northwest Shanxi, spraying 11.01 g hm-2 sodium selenite on the leaves of Jinqiao 6 at the flowering stage was the most effective selenium biofortification program. © 2022 Society of Chemical Industry.

Selenium modulated gut flora and promoted decomposition of methylmercury in methylmercury-poisoned rats.

INTRODUCTION: Selenium plays important roles in antagonizing the toxicity of methylmercury. The underlying mechanism for the antagonism between Se and MeHg is still not fully understood. OBJECTIVE: The role of gut flora against the toxicity of environmental contaminants is receiving more and more attention. The objective of this study was to investigate the role of Se against MeHg-poisoning in the modulation of gut flora and the decomposition of MeHg. METHODS: MeHg-poisoned rats were treated with sodium selenite every other day for 90 days. Fecal samples were collected on Day 8, 30, 60 and 90. Gut flora in feces was determined using 16S rRNA gene profiling, and the concentrations of Se and total mercury (THg) were measured by ICP-MS, and the concentration of MeHg was measured by CVAFS. RESULTS: Gut flora at both the ranks of phylum and genus in the MeHg-poisoned rats after Se treatment was modulated towards that in the control group, suggesting the restoration of the profile of gut flora. Increased THg was found in fecal samples after Se treatment on day 30. The percentage of MeHg (of total mercury) in the MeHg-poisoned group was in the range of 81-105% while it was 65-84% in the Se treatment group on different days, suggesting the increased decomposition of MeHg in MeHg-poisoned rats after Se treatment. CONCLUSIONS: This study suggests that MeHg poisoning damaged the abundance of gut flora and decreased their capacity for the decomposition of MeHg. After Se treatment, the abundance of gut flora was partially restored and the decomposition and excretion of MeHg was enhanced. These findings suggest that the modulation of gut flora may be one way to promote the health status in MeHg-poisoned rats and possibly in human beings.

Zea mays L. Grain: Increase in Nutraceutical and Antioxidant Properties Due to Se Fortification in Low and High Water Regimes.

This work aimed to investigate the effect of selenium (Se) and irrigation on the grain yield, on the forms of Se, phenols, and carotenes, and on some antioxidant activities of maize ( Zea mays L.) grains. To reach this goal, a 2 year experiment was undertaken. Maize was fertigated with sodium selenite at the rate of 200 g of Se ha-1 and grown under two water regimes. While the irrigation did not show a clear effect on the selected parameters, Se fertigation increased the contents of inorganic and organic Se forms, xanthophyll, and salicylic acid. Furthermore, while Se fertigation decreased the hydroxycinnamic acid content, generally higher antioxidant activities were found in Se-treated grains than in the control. These findings suggest that Se fertigation increases most of the nutraceutical values of maize grains, which therefore might improve human and livestock health and could increase the maize grain shelf life and its byproducts.

Effects of sodium selenite and L-selenomethionine on feed intake, clinically relevant blood parameters and selenium species in plasma, colostrum and milk from high-yielding sows.

A field study in periparturient sows fed different dietary concentrations of either sodium selenite or L-selenomethionine (SeMet) was conducted to evaluate feed intake, haematological and biochemical parameters as well as to describe some key selenium (Se) species, namely selenoprotein P (SelP), selenoalbumin (SeAlb) and selenomethionine (SeMet) as well as total Se in plasma, colostrum and milk. Thirty-two sows were allotted to four treatments from 30 days (d) prepartum throughout on average a 32 d lactation period. Sodium selenite supplemented diets contained 0.40 and 0.60 mg Se/kg feed, while SeMet supplemented feed contained 0.26 and 0.43 mg Se/kg feed. Concentrations of sodium selenite and SeMet in complete feed exceeded the upper limits for total dietary Se and added organic Se, respectively, according to the European Union legislation. Blood samples were collected at initiation of the study, at farrowing and at weaning. Colostrum samples were collected at farrowing and milk samples at weaning. Se species were subjected to liquid chromatography, and total Se and Se species were determined using inductively coupled plasma mass spectrometry. The SeMet supplemented diets resulted in higher feed intake and in higher levels of total Se, SelP, SeAlb and SeMet in colostrum compared with sows fed sodium selenite. Similar results were obtained for levels of total Se and SeMet in milk at weaning. The higher dietary sodium selenite concentration in sows' feed did not increase the Se transfer into colostrum or milk when compared with those receiving the lower level of sodium selenite. However, the increase in serum-Zn from initiation until farrowing, observed in sows fed SeMet as well as the higher glutamate dehydrogenase activity in sodium selenite supplemented sows in this period might indicate a higher requirement of antioxidant defence in sodium selenite-supplemented sows. To our knowledge, the present data on Se species in plasma, colostrum and milk of sows represent the most complete investigation of Se in sows conducted to date. A higher amount of the above-mentioned Se species in the colostrum of sows supplemented with SeMet might strengthen the piglets' antioxidative system and passive immunity as well as improve their average daily weight gain. The higher feed intake in sows fed diets supplemented with SeMet is an interesting finding that warrants further investigation.

Effects of Different Selenium Sources on Laying Performance, Egg Selenium Concentration, and Antioxidant Capacity in Laying Hens.

Supplementation of selenium (Se) is a common practice in the poultry industry via sodium selenite (SS) and selenium yeast (SY), while the effects of nano-selenium (NS) on laying hens are poorly known. This study aimed to compare the effects of NS, SS, and SY on productivity; selenium (Se) deposition in eggs; and antioxidant capacity in laying hens. A total of 288 30-week-old Brown Hy-line laying hens were randomly assigned into four dietary treatments, which included corn-soybean meal basal diet (Con) without Se sources and basal diets supplemented with 0.3 mg Se/kg as SS, SY, or NS, respectively. The results exhibited that Se-supplemented treatments achieved greater egg production, egg weight, and daily egg mass, also better feed conversion ratio than Con group (p < 0.05). Se supplementation significant increased egg Se concentration and decreased the egg Se deposition efficiency (p < 0.05), while SY or NS supplementation had higher Se deposition efficiency than SS group at 35 days (p < 0.05). Moreover, serum glutathione peroxidase (GSH-Px) activity increased in SS or NS group compared to Con group (p < 0.05). The glutathione peroxidase 4 (GPX-4) mRNA levels in liver were significantly higher (p < 0.05) in SS or SY group than in NS group, and mRNA levels of the methionine (Met) metabolism gene glycine N-methyltranserfase (GNMT) were markedly upregulated (p < 0.05) in SY group compared to SS or NS group. Taken together, the results revealed Se from SY is deposited into eggs more efficiently than Se from NS or SS, probably via enhancing the route of Met metabolism. Meanwhile, it might be concluded that SS or SY supplementation directly regulated GSH-Px activity via enhancing GPx4 level, whereas NS via GPx1, thus affecting body oxidation and development.

Accumulation, mobilization, and transformation of selenium in rice grain provided with foliar sodium selenite.

BACKGROUND: Selenium is an indispensable trace element for humans and its deficiency can lead to serious health complications. Nearly 70% of the area of China faces selenium deficiency. To deal with this problem, selenium-enriched rice has been increasingly incorporated into everyday diets. However, there is a lack of in-depth studies of the absorption, translocation, and transformation of selenium in the different parts of the rice plant when sprayed with sodium selenite. RESULTS: Foliar sodium selenite applied at critical growth stages can significantly improve the total and organic selenium content of plants. Application of 10 mg L-1 sodium selenite led to the most organic selenium (0.03 mg kg-1 ) in polished rice. Correlation studies of sodium selenite applied to leaves and other plant parts showed that total selenium accumulated most in glume, followed by rice bran, then polished rice, and finally embryo. The behavior of organic selenium was different. Organic selenium accumulated most in polished rice, then embryo, then rice bran, and finally glume. Moreover, 75-85% of the Se found in polished rice and embryo was organic in nature. CONCLUSIONS: We propose that 10 mg L-1 sodium selenite can be recommended as appropriate for foliar fertilization in the organic selenium biofortification of Se-free rice. © 2018 Society of Chemical Industry.

Assessment of selenium bioaccumulation in lactic acid bacteria.

Selenium is an essential micronutrient for living beings, as it helps to maintain the normal physiological functions of the organism. The numerous discoveries involving the importance of this element to the health of human beings have fostered interest in research to develop enriched and functional foods. The present study evaluated the potential for bacterial strains of Enterococcus faecalis (CH121 and CH124), Lactobacillus parabuchneri (ML4), Lactobacillus paracasei (ML13, ML33, CH135, and CH139), and Lactobacillus plantarum (CH131) to bioaccumulate Se in their biomass by adding different concentrations of sodium selenite (30 to 200 mg/L) to the culture medium. Quantification of Se with UV and visible molecular absorption spectroscopy showed that the investigated bacteria were able to bioaccumulate this micromineral into their biomass. Two of the L. paracasei strains (ML13 and CH135) bioaccumulated the highest Se concentrations (38.1 ± 1.7 mg/g and 40.7 ± 1.1 mg/g, respectively) after culture in the presence of 150 mg/L of Se. This bioaccumulation potential has applications in the development of dairy products and may be an alternative Se source in the diets of humans and other animals.

Selenium Supplementation Changes the Ion Profile in the Pancreas of Chickens Treated with Cadmium.

Increasing evidence indicates that selenium (Se) could antagonize metal toxicity, including cadmium (Cd) toxicity. However, the effects of Se on Cd-induced changes in the ion profile in the pancreas of chickens have not been reported. In the present study, 128 Hy-Line brown laying chickens were divided into the control group, Se-treated group, Se/Cd-treated group, and Cd-treated group, and we detected the concentrations of 28 ions in the four groups by inductively coupled plasma mass spectrometry. In the Cd-treated group, the accumulation of Cd in the pancreas was 836.8 times higher that than in the control group (27,353.71 ppb/32.69 ppb). Meanwhile, the Ca, Ti, Fe, Mo, Li, Al, and Pb levels increased and the Cr, Mn, Ni, Cu, Zn, Se, Sr, and Sb levels decreased due to sub-chronic Cd poisoning. The Fe, Mo, Ba, and Pb levels decreased in the Se/Cd-treated group. Our findings suggest that Cd can accumulate in the chicken pancreas and affect the ion profiles, whereas Se can ameliorate the accumulation of Cd and change the ion profiles in the chicken pancreas.

Selective fluorescence detection method for selenide and selenol using monochlorobimane.

The low redox potential of selenide and selenol is physiologically important, as it confers efficient catalytic abilities to selenoproteins. Quantitative determination of selenol and selenide provide important clues for understanding the metabolism and physiological function of selenium. However, selective detection of selenol and selenide is extremely difficult because of their chemical similarity to thiol and sulfide. In this study, we established a highly sensitive, selective, quantitative, and simple method for detection of selenol and selenide, using a reaction with monochlorobimane (MCB), followed by ethyl acetate extraction of the product syn-(methyl,methyl)bimane. We analyzed selenide production from selenite, catalyzed by human glutathione reductase, and also determined selenide and selenol concentrations in Hepa1-6 cells using the MCB method, to demonstrate its practical applications. This study provides a new tool for selenium detection in biology.

Biochemical Comparison of Commercial Selenium Yeast Preparations.

The trace mineral selenium (Se) is an essential element for human and animal nutrition. The addition of Se to the diet through dietary supplements or fortified food/feed is increasingly common owing to the often sub-optimal content of standard diets of many countries. Se supplements commercially available include the inorganic mineral salts such as sodium selenite or selenate, and organic forms such as Se-enriched yeast. Today, Se yeast is produced by several manufacturers and has become the most widely used source of Se for human supplementation and is also widely employed in animal nutrition where approval in all species has been granted by regulatory bodies such as the European Food Safety Authority (EFSA). Characterisation and comparison of Se-enriched yeast products has traditionally been made by quantifying total selenomethionine (SeMet) content. A disadvantage of this approach, however, is that it does not consider the effects of Se deposition on subsequent digestive availability. In this study, an assessment was made of the water-soluble extracts of commercially available Se-enriched yeast samples for free, peptide-bound and total water-soluble SeMet. Using LC-MS/MS, a total of 62 Se-containing proteins were identified across four Se yeast products, displaying quantitative/qualitative changes in abundance relative to the certified reference material, SELM-1 (P value <0.05; fold change ≥2). Overall, the study indicates that significant differences exist between Se yeast products in terms of SeMet content, Se-containing protein abundance and associated metabolic pathways.

A simplified method for inorganic selenium and selenoaminoacids speciation based on HPLC-TR-HG-AFS.

A simplified speciation method for the determination of selenite, selenate and three selenoaminoacids (selenocystine, selenomethylselenocysteine and selenomethionine) has being developed, based on the coupling of high performance liquid chromatography (HPLC), thermoreduction (TR), hydride generation (HG) and atomic fluorescence spectrometry (AFS). Most of the existing methods based on AFS detection employ a two step procedure to reduce selenate to selenite before HG: (i) Ultraviolet radiation followed by (ii) heating, to produce volatile hydrides of the selenium compounds. The proposed simplified method HPLC-TR-HG-AFS does not require ultraviolet radiation. Instead, KBr dissolved in a HCl solution is added during the heating step (thermoreduction), resulting in an effective hydride generation of the selenium species. Different variables (temperature, HCl and NaBH4 concentrations) have been optimized, using both univariant and multivariant experimental designs. The proposed method is therefore less complex and allows limits of detection, reproducibility and repeatability values similar or better than the existing AFS detection methods described in the literature. A Certified Reference Material (SELM-1 with certified selenomethionine content) and a Se-enriched algae sample have been successfully analyzed with the proposed method. The results were also compared to an alternative technique (GC-MS) that provided similar results.

Selenium bioaccessibility and bioavailability in Se-enriched food supplements.

Most European people have selenium (Se) intake inferior to recommended values that are considered necessary to ensure the beneficial action of antioxidant selenoproteins. People could therefore tend to have recourse to Se-enriched food supplements (FS) aiming to increase their Se body level. On the Belgian market, three main types of Se-rich FS are available: Se-enriched yeast, selenate-based FS, and selenite-based FS. In the present work, in vitro tests imitating gastrointestinal digestion and intestinal absorption were used to determine the bioaccessible and bioavailable fractions of Se present in one specimen of each category of FS. The aim of the study was to verify to which extent the difference in Se speciation could influence the efficiency of FS for enhancing the human Se status. Results indicated that differences exist in both bioaccessibility and bioavailability between the three types of FS, and that these differences could be related, at least partially, to the Se species profile. Overall bioavailability of the three FS was low (maximum 14 % of the original Se content). Among the three samples, the selenate-based FS produced the highest fraction of bioavailable Se, followed by Se-yeast, and finally by the selenite-based FS for which Se was almost not available at all. These results confirm the low availability of inorganic Se but were somewhat unexpected regarding the yeast-based FS since Se-rich yeasts are usually reported to contain an important fraction of available Se.

Evaluation of the potential of peas (Pisum sativum L.) to be used in selenium biofortification programs under Mediterranean conditions.

Selenium (Se), which has antioxidant, anticancer, and antiviral properties, is an essential micronutrient for humans and animals. This micronutrient is found in high quantity in legumes. Peas have an ever-increasing importance in Spain, and to increase their nutritional value, two foliar Se fertilizers: sodium selenate and sodium selenite, at five different rates: 0, 10, 20, 40, 80 g ha(-1), were studied during the 2010/2011 crop season on semiarid Mediterranean conditions. Sodium selenate was much more effectively taken up by plants compared to sodium selenite. There was a strong linear relationship between the total Se content and Se rate in both sodium selenate and selenite. For each gram of Se fertilization as either sodium selenate or sodium selenite, the increase of total Se concentration in the grain was 148 and 19 µg Se kg(-1) dry weight, respectively. Ingestion of 100 g of peas previously fertilized with 10 g of sodium selenate per hectare would result in an intake of 179 µg of Se. This is almost 90 % of the daily recommended dose needed to reduce the chance of some cancers and about 179 % of the minimum concentration required to prevent Se deficiency diseases in animals. The pea has shown to have a strong ability to uptake and accumulate Se under Mediterranean conditions; therefore, this would make it a very strong candidate for inclusion in biofortification programs aiming to increase Se in the food chain.

Selenium species and their distribution in freshwater fish from Argentina.

The distribution and speciation of selenium (Se) in freshwater fish (muscle and liver tissue) from lakes in Argentina was investigated. Three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis), and one native species, creole perch (Percichthys trucha), were investigated. Values for total selenium in muscle ranged from 0.66 to 1.61 µg/g, while in the liver, concentrations were much higher, from 4.46 to 73.71 µg/g on a dry matter basis. Separation of soluble Se species (SeCys(2), selenomethionine (SeMet), SeMeSeCys, selenite and selenate) was achieved by ion exchange chromatography and detection was performed by inductively coupled plasma-mass spectrometry. The results showed that in fish muscle, from 47 to 55 % of selenium was soluble and the only Se species identified was SeMet, which represented around 80 % of soluble Se, while in the liver, the amount of soluble Se ranged from 61 to 76 % and the percentage of species identified (SeMet and SeCys(2)) was much lower and ranged from 8 to 17 % of soluble Se.

Online preconcentration-IC-ICP-MS for selenium quantification and speciation at ultratraces.

Selenium (Se) is of key importance to human health with a very narrow concentration range of optimal dietary intake. Due to the inherent analytical challenge linked with the low natural abundance, information on precise and accurate Se speciation in deficient environments is hardly existent. This study presents a novel approach to determine Se species-specifically at ultratraces, by online coupling of a preconcentration (trap) column to an ion chromatography inductively coupled plasma mass spectrometry (IC-ICP-MS) system. It is demonstrated that with this robust and work/time efficient method, the predominant selenium oxyanions, selenite (Se(IV)) and selenate (Se(VI)), can be quantified down to 7.3 and 8.3 picogram total Se, respectively, in an overall analytical time of 420 s, only. The applicability for environmental samples was proven on pristine volcanic ashes collected from seven different volcanoes. The high sensitivity of the novel approach allowed to determine speciation in samples that were strongly depleted in total selenium (<0.05 mg kg(-1) Se) with only minor fractions of Se mobilized (i.e., less than 10% of the total selenium was leached in 10 out of 12 samples). The studied samples showed considerate differences in selenium speciation, with selenite and selenate co-occurring in most samples. The fact that the studied sample leachates had a wide range of pH (3.78-9.55) and major anion/cation composition underlines the versatility and wide potential application range of the method presented.

Selenium bioaccumulation in shiitake mushrooms: a nutritional alternative source of this element.

UNLABELLED: Mushrooms have effective mechanisms to absorb and accumulate trace elements from substrates and, therefore could be used as a strategy to produce mineral-enriched food and nutritional supplements. This study aimed to enrich shiitake mushrooms with selenium (Se), an important dietary element in human health. Strains of Lentinula edodes (Berk.) were grown on artificial logs composed of eucalyptus sawdust, and were subjected to cold shock in water containing sodium selenite (Na(2)SeO(3) ) at concentrations of up to 1.28 mM. The content of Se in the mushrooms increased linearly with increasing amounts of Na(2)SeO(3) added to the cold water although above 0.96 mM, mushroom formation was inhibited. Concentrations greater than 17 mg Se 100/g of dried mushrooms were observed after treatment with 0.64 mM Na(2)SeO(3). Shiitake mushroom had a demonstrate potential to offer an effective and economical way to produce Se-enriched products and, the strategy of adding selenite in cold water, used in this study, showed promising once it does not interfere with mycelial growth. PRACTICAL APPLICATION: Selenium is an essential trace element for both human and animals and is required for the 21st amino acid, selenocysteine, which is used for the synthesis of about a dozen selenoenzymes. In this study, it is demonstrated that shiitake mushroom is a good Se accumulator and only one step during fructification was necessary to obtained enriched mushroom. Se enriched shiitake mushroom can be considered to be an excellent source of this element and used to consumption in different ways.

Selenium adsorption and speciation with Mg-FeCO3 layered double hydroxides loaded cellulose fibre.

A novel adsorbent was developed by coating Mg-FeCO(3) layered double hydroxides (LDHs) on cellulose fibre. The LDHs take up significant amount of selenite and selenate in a wide pH range with similar sorption capacities (pH 3.8-8.0 for selenite and pH 5.8-7.0 for selenate). A mini-column packed with Mg-FeCO(3) LDHs layer coated cellulose fibre particles was incorporated into a sequential injection system for uptake of selenite at pH 6.0. The retained selenite was afterwards collected with 70 µ L of 0.8%(m/v) NaOH as eluent, followed by hydride generation and atomic fluorescence spectrometric detection. Total inorganic selenium was adsorbed at pH 6.0 by the LDHs-cellulose fibre mini-column after selenate was pre-reduced to selenite by 2.0 mol L(-1) HCl at 80°C, and selenium speciation was performed by difference. With a sample volume of 1.0 mL, an enrichment factor of 13.3 was derived with a detection limit of 11 ng L(-1) within a linear range of 0.04-4.0 µg L(-1). A relative standard deviation (RSD) of 3.3% (0.5 µg L(-1), n=11) was achieved. The procedure was validated by analyzing selenium in a certified reference material GBW 10010 (rice), and speciation of inorganic selenium in natural water samples.

Distribution and metabolism of selenite and selenomethionine in the Japanese quail.

Compared to the many studies on the physiological and toxicological effects of selenium (Se) in mammals, avian Se metabolism is still an unexplored topic. Some birds are useful as poultry for human nutrition. Moreover, birds belong to higher trophic levels in the biosphere and thus may play an important role in Se circulation in the ecosystem in the same way as mammals do. In this study, we analyzed the distribution and metabolism of Se in an experimental bird, the Japanese quail, which was fed drinking water containing sodium selenite or selenomethionine (SeMet). The highest concentration of Se was detected in the pancreas, followed by down feathers, liver, and kidneys. SeMet was more efficiently incorporated into the quail than selenite. The specific and preferable distribution of Se to the high molecular weight fraction in the serum of the quail was observed only in the SeMet-ingestion group. As in mammals, selenosugar and trimethylselenonium were the major metabolites in quail excreta. Three unknown Se metabolites were detected by HPLC-ICP-MS. Although part of the metabolic pathway of Se in the Japanese quail fed selenite and SeMet was the same as that observed in mammals, the bird also showed certain avian-specific metabolic process for Se.

Bioaccumulation and transformation of methylmercury and selenite using zebrafish (Danio Rerio) larvae as a model.

Bioaccumulation and possible transformation of methylmercury and selenite has been checked on a 72 h-cycle of bioaccumulation and depuration using larvae from zebrafish. The larvae were exposed to methylmercury and selenite at concentrations of 1% and 0.1% of their LC(50) values. Quantitative extraction of methylmercury and selenite from exposed larvae was achieved by using ultrasonic probe-assisted extraction (USP), thus reducing extraction time and solvent consumption. Extracted species collected at different exposure times were characterized and quantified by liquid chromatography coupled to ICP-MS. Bioconcentration factors (BCFs) were estimated by two procedures: (i) as the ratio of the contaminant concentration in larvae and exposure media (BCF(48 h)) and (ii) fitting contaminant concentration in larvae to bioaccumulation models that describe uptake and depuration processes (BCF(k)). The BCFs obtained for methylmercury were 5000 and 2333 for larvae exposed to 1 µg L(-1) and 10 µg L(-1), respectively; while for selenite the BCF was 74 for larvae exposed to 10 µg L(-1). The good correlation between the BCFs found and those previously reported in the literature shows the proposed method as a good and promising alternative to the OECD Bioconcentration Test 305. Actually, the use of zebrafish larvae reduces the bioaccumulation test time from forty two (OECD Bioconcentration Test 305) to three days. In addition, potential biotransformation of both methylmercury and selenite was evaluated by LC-ICP-MS. For this purpose, a method for species extraction in small size samples by using ultrasonic probe sonication was developed.

Selenite biotransformation during brewing. Evaluation by HPLC-ICP-MS.

Yeast (Saccharomyces cerevisiae) and lactic bacteria have shown their ability to accumulate and transform inorganic selenium into organo Se compounds. The objective of this work was to evaluate selenium biotransformation during brewing by using S. cerevisiae and Saccharomyces uvarum for Ale and Lager fermentation, respectively. Se-enriched beer was produced by the addition of sodium selenite (0, 0.2, 1.0, 2.0, 10.0, 20.0 µg Se mL(-1), respectively) to the fermentation media composed of yeast, malt extract and water. The alcoholic fermentation process was not affected by the presence of selenium regardless of the type of Saccharomyces being used. The percentage of selenium incorporated into beer, added between 1.0 and 10 µg mL(-1) was 55-60% of the selenium initially present. Se-compounds in post-fermentation (beer and yeast) products were investigated by using an analytical methodology based on HPLC-ICP-MS. For this purpose, several sample treatments, including ultrasonic-assisted enzymatic hydrolysis, in conjunction with different separation mechanisms like dialysis and anion exchange HPLC chromatography were applied for unambiguously identifying Se-species that produce during brewing. Selenomethionine was the main selenium compound identified in beer and yeast, being this species in the only case of the former not associated to peptides or proteins.