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Selenium yeast

From Wikipedia, the free encyclopedia

Selenium yeast is Saccharomyces cerevisiae (baker's yeast) grown in a selenium-rich media.[1] It contains selenium in the form of organic and inorganic compounds. It is used both as a feed additive for livestock and as a dietary supplement for humans. It is approved in the US, EU, and the UK.[2] Because selenium yeast can be patented, its producers can demand premium prices.[3]

The other source of selenium is inorganic selenium in the form of pure chemicals. Forms used in animal feed include sodium selenate and sodium selenite. These too are effective in supplying selenium to the livestock.[3]

The main claimed benefit of selenium yeast is that it contains organic selenium, mainly in the form of selenomethionine and selenocystine-containing proteins. Because these organic chemicals are also found in common natural sources of selenium such as wheat, it is claimed that they are more easily absorbed by animals including humans.[1][4] Unfortunately, there is considerable variability in products described as "selenium yeast", specifically in the selenium compounds found within. Many products on the market are simply mixtures of largely inorganic selenium and some yeast, which defeats the point of using selenium yeast.[5]

Molecular biology

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Yeast cell walls are able to bind to inorganic selenium-containing ions via chemisorption. The ions do not pass through the cell membrane, so special transporter proteins are required to let them in. Inside of the yeast cell, the selenium is reduced to hydrogen selenide. With usual amounts of selenium, this ends in the regular tRNA pathway of selenoprotein production.[6]

However, selenium yeast is grown in amounts of selenium beyond usual. At this concentration, promiscuous enzymes which do not effectively distinguish sulfur and selenium start to make selenium analogs of sulfur organic compounds. In this other pathway, selenide first becomes homoselenocysteine. On one branch of the pathway, homoselenocysteine is converted to selenomethionine, Se-adenosyl selenomethionine, Se-adenosyl-homoselenocysteine and back to homoselenocysteine (the seleno version of the S-adenosyl methionine cycle). On the other branch, homoselenocysteine is converted to selenocystathionine, then selenocystine, Se-methylselenocysteine, and γ-glutamyl-Se-methylselenocysteine.[6] At this level of excess, both selenomethionine and selenocystine can be randomly incorporated into proteins in lieu of the regular amino acid.[7] The net effect is that the yeast is used to convert inorganic selenium into organic selenium stored in its body.[6]

The beyond-normal levels of selenium can be toxic to the yeast itself. Excess amounts of random misincorporation, especially of selenocystine, can lead to non-functional proteins aggregating in the cell.[7] The selenium accumulator plant Astragalus bisulcatus has a more selective version of the cystine-tRNA ligase that reduces the chances of misincorporation of selenocystine when put in yeast. This genetic modification is, however, not expected to be used in selenium yeast as a food ingredient, but for use in the production of designer proteins in biotechnology.[8]

Animal feed additive

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Main article: Selenium in biology

Large amounts of selenium are toxic; however, it is physiologically necessary for animals in extremely small amounts. Many other uncharacterized selenium-containing organic chemicals are also produced by a method similar to that of selenomethionine; some have recently been characterized but remain relatively unknown, such as S-seleno-methyl-glutathione and glutathione-S-selenoglutathione.[1][5] Due to this, the European Union has questioned the safety and potential toxicity of this food supplement for humans, and it may not be used as an additive after 2002.

G.N Schrauzer, who has written two papers about selenomethionine, claims it should be an essential amino acid, and that the product is completely safe.[1] The European Food Safety Authority does allow the use of selenomethionine as a feed additive for animals.[9] Because organic forms of selenium appear to be excreted from the body slower than inorganic forms, products enriched with organic selenium might detrimentally bioaccumulate in the body. Because selenium-enriched foods contain much more selenium than natural foods, selenium toxicity is a potential problem, and such foods must be treated with caution.[5] The EU allows up to 300 micrograms of selenium per day, but one long-term study of selenium supplementation showed no evidence of toxicity at a dose as high as 800 micrograms per day.[10]

An organic selenium-containing chemical found in selenium yeast has been shown to differ in bioavailability and metabolism compared with common inorganic forms of dietary selenium.[11] Dietary supplementation using selenium yeast is ineffective in the production of antioxidants in bovine milk compared to inorganic selenium (sodium selenate).[12] One study examined if increased selenium in the diet of mutant mice (via a selenium yeast product) caused a higher production of selenium-containing enzymes which have an antioxidant effect. The effect was modest.[13]

Selenium supplementation in yeast form has been shown to increase pig selenium-containing antioxidant enzymes,[14] broiler growth and meat quality,[15][16] the shelf life of turkey and rooster semen,[17][18][19] and possibly cattle fertility.[20]

Selenium supplementation in animal feeds may be profitable for agribusinesses. It may be possible to market selenium-fortified foods to consumers as functional foods, such as selenium-enriched eggs, meat,[21][22][23][24] or milk.[12]

Specific products

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Sel-Plex

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A patented cultivar of yeast (Saccharomyces cerevisiae 'CNCM I-3060') marketed as Sel-Plex® has been approved for use in animal fodder:

  • U.S. Food and Drug Administration approval for use as a supplement to feed for chickens, turkeys, swine, goats, sheep, horses, dogs, bison, and beef and dairy cows.[25]
  • Organic Materials Review Institute approval for use as a feed supplement for all animal species.[26]
  • As of 2006, the European Food Safety Authority's Scientific Panel on Additives and Products or Substances used in Animal Feed allows the use of Sel-Plex® in animal fodder for poultry, swine, and bovines, as the selenium is not significantly bio-accumulated by the human consumer.[3]

Precautions

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Only a small amount should be used when blending animal feeds. An excess of selenium, specifically at 10× the European authorized maximum selenium intake of Sel-Plex, causes a drop in animal productivity.[3]

Appropriate measures to minimize inhalation exposure to the product should be taken.[3]

Analytical chemistry

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Total selenium in selenium yeast can be reliably determined using open acid digestion to extract selenium from the yeast matrix followed by flame atomic absorption spectrometry.[27] Determination of the selenium species selenomethionine can be achieved via proteolytic digestion of selenium yeast followed by high-performance liquid chromatography with inductively coupled plasma mass spectrometry.[28][29][30]

See also

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Nutritional muscular dystrophy

References

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  1. ^ a b c d Schrauzer G (2006). "Selenium yeast: composition, quality, analysis, and safety". Pure Appl Chem. 78: 105–109. doi:10.1351/pac200678010105.
  2. ^ "Guidance notes on legislation implementing Directive 2002/46/EC on food supplements".
  3. ^ a b c d e European Food Safety Authority (2006). "Opinion of the scientific panel on additives and products or substances used in animal feed on the safety and efficacy of the product Sel-Plex®2000 as a feed additive according to regulation (EC) No 1831/2003". EFSA Journal. 4 (5): 1–40. doi:10.2903/j.efsa.2006.348.
  4. ^ Schrauzer GN (2003). The nutritional significance, metabolism and toxicology of selenomethionine. Advances in Food and Nutrition Research. Vol. 47. pp. 73–112. doi:10.1016/s1043-4526(03)47002-2. ISBN 9780120164479. PMID 14639782. {{cite book}}: |journal= ignored (help)
  5. ^ a b c Rayman M, Infante H, Sargent M (2008). "Food-chain selenium and human health: spotlight on speciation". Br J Nutr. 100 (2): 238–253. doi:10.1017/s0007114508922522. PMID 18346307.
  6. ^ a b c Kieliszek, M; Błażejak, S; Gientka, I; Bzducha-Wróbel, A (July 2015). "Accumulation and metabolism of selenium by yeast cells". Applied Microbiology and Biotechnology. 99 (13): 5373–82. doi:10.1007/s00253-015-6650-x. PMC 4464373. PMID 26003453.
  7. ^ a b Plateau, Pierre; Saveanu, Cosmin; Lestini, Roxane; Dauplais, Marc; Decourty, Laurence; Jacquier, Alain; Blanquet, Sylvain; Lazard, Myriam (17 March 2017). "Exposure to selenomethionine causes selenocysteine misincorporation and protein aggregation in Saccharomyces cerevisiae". Scientific Reports. 7 (1): 44761. Bibcode:2017NatSR...744761P. doi:10.1038/srep44761. PMID 28303947.
  8. ^ Hoffman, KS; Vargas-Rodriguez, O; Bak, DW; Mukai, T; Woodward, LK; Weerapana, E; Söll, D; Reynolds, NM (23 August 2019). "A cysteinyl-tRNA synthetase variant confers resistance against selenite toxicity and decreases selenocysteine misincorporation". The Journal of Biological Chemistry. 294 (34): 12855–12865. doi:10.1074/jbc.RA119.008219. PMID 31296657.
  9. ^ Commission of the European Communities. Commission regulation (EC) No 1750/2006 of 27 November 2006 concerning the authorisation of selenomethionine as a feed additive [online]. Available at: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:330:0009:0011:EN:PDF. Accessed January 21.
  10. ^ Rayman, Margaret P. (October 2004). "The use of high-selenium yeast to raise selenium status: how does it measure up?". British Journal of Nutrition. 92 (4): 557–573. doi:10.1079/bjn20041251. PMID 15522125. S2CID 5015850.
  11. ^ Schrauzer G. Selenomethionine: A review of its nutritional significance, metabolism and toxicity" J Nutr 2000;130:1653-1656.
  12. ^ a b Ravn-Haren G, Bugel S, Krath B, et al. (2008). "A short-term intervention trial with selenate, selenium-enriched yeast and selenium-enriched milk: effects on oxidative defence regulation". Br J Nutr. 99 (4): 883–892. doi:10.1017/s0007114507825153. PMID 17888202.
  13. ^ Lovell M, Xiong S, Lyubartseva G, Markesbery W (2009). "Organoselenium (Sel-Plex diet) decreases amyloid burden and RNA and DNA oxidative damage in APP/PS1 mice". Free Radic. Biol. Med. 46 (11): 1527–1533. doi:10.1016/j.freeradbiomed.2009.03.008. PMC 2683469. PMID 19303433.
  14. ^ Sarkuniene C, Oberauskas V, Baranauskiene D, et al. (2010). "The impact of forage additive Sel-Plex containing organic selenium (Se) on morphological and biochemical blood parameters and activity enzymes GPx and δ-ALRD in fattening pigs". Vet Med Zoot. 50: 88–92.
  15. ^ Pappas A, Acamovic T, Surai PF, McDevitt R. Maternal organo-selenium compounds and polyunsaturated fatty acids affect progeny performance and levels of selenium and docosahexaenoic acid in the chick tissues. Poult Sci 2006;85:1610-1620.
  16. ^ Zhao L, Xu S, Zhao R, Peng Z, Pan X. "Effects of selenium and methionine supplementation of breeder hen diets on selenium concentration and oxidative stability of lipids in the thigh muscles of progeny. J Food Sci 2009;74:C569-AC574.
  17. ^ Dimitrov S, Atanasov V, Surai PF, Denev S (2007). "Effect of organic selenium on turkey semen quality during liquid storage". Anim Reprod Sci. 100 (3–4): 311–317. doi:10.1016/j.anireprosci.2006.07.007. PMID 16935439.
  18. ^ Slowinska M, Jankowski J, Dietrich G, et al. (2011). "Effect of organic and inorganic forms of selenium in diets on turkey semen quality". Poult Sci. 90 (1): 181–190. doi:10.3382/ps.2010-00956. PMID 21177458.
  19. ^ Ebeid T (2009). "Organic selenium enhances the antioxidative status and quality of cockerel semen under high ambient temperature". Br Poult Sci. 50 (5): 641–647. doi:10.1080/00071660903303415. PMID 19904644. S2CID 27779405.
  20. ^ Thatcher W, Santos J, Silvestre F, Kim I, Staples C (2010). "Perspective on physiological⁄endocrine and nutritional factors influencing fertility in post-partum dairy cows". Reprod Dom Anim. 45: 2–14. doi:10.1111/j.1439-0531.2010.01664.x. PMID 24417194.
  21. ^ Surai PF, Karadas F, Pappas A, Sparks N (2006). "Effect of organic selenium in quail diet on its accumulation in tissues and transfer to the progeny". Br Poult Sci. 47 (1): 65–72. doi:10.1080/00071660500475244. PMID 16546799. S2CID 19679504.
  22. ^ Navas-Carretero S, Cuervo M, Abete I, Zulet M, Martinez J (2010). "Frequent consumption of selenium-enriched chicken meat by adults causes weight loss and maintains their antioxidant status". Biol Trace Elem Res. 143 (1): 8–19. doi:10.1007/s12011-010-8831-x. PMID 20809267. S2CID 8561408.
  23. ^ Fisinin V, Papazyan T, Surai PF (2009). "Producing selenium-enriched eggs and meat to improve the selenium status of the general population". Crit Rev Biotechnol. 29 (1): 18–28. doi:10.1080/07388550802658030. PMID 19514900. S2CID 35928188.
  24. ^ Mahan D. Organic selenium fed to swine - its potential impact on human health issues. In: Midwest Swine Nutrition Conference. Indianapolis, IN, 2005.
  25. ^ Sel-Plex receives authorisation [online]. Available at: http://www.allaboutfeed.net/news/sel-plex-receives-authorisation-id98.html. Accessed January 21.
  26. ^ Organic Materials Review Institute. Sel-Plex [online]. Available at: http://www.omri.org/simple-opl-search/results/sel-plex. Accessed January 21.
  27. ^ Connolly C, Power R, Hynes M (2004). "Validation of method for total selenium determination in yeast by flame atomic absorption spectrometry". Biol Trace Elem Res. 100 (1): 87–94. Bibcode:2004BTER..100...87C. doi:10.1385/bter:100:1:087. PMID 15258322. S2CID 28815488.
  28. ^ European Food Safety Authority. Selenium-enriched yeast as source for selenium added for nutritional purposes in foods for particular nutritional uses and foods (including food supplements) for the general population: Scientific opinion of the panel on food additives, flavourings, processing aids and materials in contact with food. EFSA Journal 2008;766:1-42.
  29. ^ B'Hymer C, Caruso J (2006). "Selenium speciation analysis using inductively coupled plasma-mass spectrometry". J Chromatogr A. 1114 (1): 1–20. doi:10.1016/j.chroma.2006.02.063. PMID 16551466.
  30. ^ Lobinski R, Edmonds J, Suzuki K, Uden P (2000). "Species-selective determination of selenium compounds in biological materials". Pure Appl Chem. 72 (3): 447–461. doi:10.1351/pac200072030447.
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