Accumulation and species distribution of selenium in Se-enriched bacterial cells of the Bifidobacterium animalis 01

Bifidobacterium animalis 01 (B. animalis 01) could absorb 16.7–39.6% of inorganic selenium in the medium and transform most of it into organic selenium. Most of the organic selenium (50.7–63.0%) was found in the protein fraction, 9.62–18.7% in the polysaccharide fraction, 0.273–0.754% in the nucleic acid fraction, and 20.8–30.9% in other components. Furthermore, the selenium content of different protein extractions was in the following order: Alkaline-soluble protein-bound Se (46.5–53.4%) > Water-soluble protein-bound Se (27.4–30.8%) > Salt-soluble protein-bound Se (7.79–11.9%) > Alcohol-soluble protein-bound Se (not detected). Additionally, the molecular mass of most proteins or protein subunits containing selenium was about 10–20 kDa. Analysis by LC–MS showed that selenomethionine (SeMet) is the major selenocompound in protein.