Selenium Yeast (Selenium-Enriched Yeast)

Selenium yeast is produced by culturing Saccharomyces cerevisiae on a medium enriched with sodium selenite as the selenium source. The growing yeast substitutes selenium for sulphur during protein synthesis, so the selenium ends up covalently bound within yeast protein — predominantly as L-selenomethionine — rather than sitting on the biomass as a residual inorganic salt. The culture is then heat-inactivated, washed and dried to a free-flowing light beige to brown powder. It is a fermentation product, not a dry blend of yeast with a selenium salt, and it is this distinction that buyers are paying for. The specification framework is set by two European instruments. For food supplements, Annex II of Directive 2002/46/EC as amended by Commission Regulation (EU) No 1170/2009 defines selenium-enriched yeasts as produced by culture in the presence of sodium selenite and containing, in the dried form as marketed, not more than 2.5 mg Se/g; selenomethionine is the predominant organic selenium species at between 60 and 85% of total extracted selenium, other organic selenium compounds including selenocysteine must not exceed 10% of total extracted selenium, and inorganic selenium normally must not exceed 1% of total extracted selenium. Under the EU feed authorisation 3b813 (Commission Implementing Regulation (EU) No 427/2013) the corresponding preparation carries 1,000 to 2,650 mg Se/kg, with organic selenium above 98% and selenomethionine above 70% of total selenium. Selenium is an essential trace element and a constituent of selenoproteins such as glutathione peroxidase and thioredoxin reductase; the yeast form is specified where a protein-bound, food-form selenium source is preferred over an inorganic salt. Thovek supplies selenium yeast at 1,000 ppm and 2,000 ppm total selenium, milled to a low-dust free-flowing powder that blends well at the low inclusion rates involved. Total selenium is determined by ICP-MS after microwave digestion, selenomethionine by HPLC-ICP-MS after triple proteolytic digestion, and selenium in premixes and finished feed by hydride generation atomic absorption spectrometry to EN 16159:2012. Every batch ships with a full CoA covering selenium speciation, heavy metals, moisture and microbiology, together with MSDS, allergen, non-GMO and Certificate of Origin documentation.