Determination of Selenium Speciation in High Se-Enriched Edible Fungus Ganoderma lucidum Via Sequential Extraction

Abstract

Edible fungi are often used as an important selenium (Se) source to improve human daily Se intakes as food or Se supplements because of their strong ability to accumulate Se, in which Ganoderma lucidum was widely accepted in China. However, the existing Se speciation analysis methods such as protease K-based or trypsin-protease XIV-based, have low extraction rate and enzymatic hydrolysis rate (<30%) on the Se-enriched edible fungi, resulting that it is impossible to effectively evaluate Se transformation and safety of Se-enriched edible fungi. In order to improve the extraction rate and enzymatic hydrolysis rates, 12 extraction methods (combination of buffer solutions and enzymes) including 4 two-step extraction methods and 8 three-step extraction methods were applied to extract Se from high Se-enriched Ganoderma lucidum (Total Se content 245.7 μg/g in dry matter (DW)) in the present study. The results displayed that one three-step sequential extraction method as aqueous solution extraction-pepsin extraction-trypsin extraction performed the best, by which the total Se extraction rate could reach 65%, the total Se enzyme hydrolysis rate was 40%, and the Se speciation was revealed as Selenite (63.6%), SeCys2 (20.1%), SeMeCys (14.8%) and SeMet (1.5%) in this high Se-enriched Ganoderma lucidum. This study offers a reliable and efficient method to evaluate the Se transformation and the Se safety in high Se-enriched edible fungi.