Selenium uptake, toxicity and reduction in Flammulina velutipes supplied with selenite

Recently, selenium (Se) enriched mushrooms have been exploited as diary Se supplements, but our knowledge of the metabolism process during the Se enrichment process is far from complete. In this study, the uptake, toxicity and reduction of selenite in a widely cultivated mushroom, Flammulina velutipes , was investigated. The results showed that pH variation (from 5.5 to 7.5), metabolic inhibitor (0.1 mM 2,4-DNP) and P or S starvation led to 11%-26% decreases in the selenite uptake rate of F. velutipes . This indicates that a minor portion of the selenite uptake was metabolism dependent, whereas a carrier-facilitated passive transport may be crucial. Growth inhibition of F. velutipes initiated at 0.1 mM selenite (11% decrease in the growth rate) and complete growth inhibition occurred at 3 mM selenite. A selenite concentration of 0.03-0.1 mM was recommended to maintain the balance between mycelium production and Se enrichment. F. velutipes was capable of reducing selenite to Se(0) nanoparticles, possibly as a detoxification mechanism. This process depended on both selenite concentration and metabolism activity. Overall, the data obtained provided some basic information for the cultivation of the selenized F. velutipes , and highlighted the opportunity of using mushrooms for the production of Se(0) nanoparticles. Abstract: Recently, selenium (Se) enriched mushrooms have been exploited as diary Se 12 supplements, but our knowledge of the metabolism process during the Se enrichment process is 13 far from complete. In this study, the uptake, tolerance and reduction of selenite in a widely 14 cultivated mushroom, Flammulina velutipes , was investigated. The results showed that pH 15 variation (from 5.5 to 7.5), metabolic inhibitor (0.1 mM 2,4-DNP) and P or S starvation led to 11%-16 26% decreases in the selenite uptake rate of F. velutipes . This indicates that a minor portion of 17 the selenite uptake was metabolism dependent, whereas a carrier-facilitated passive transport 18 may be crucial. Growth inhibition of F. velutipes initiated at 0.1 mM selenite (11% decrease in 19 the growth rate) and complete growth inhibition occurred at 3 mM selenite. A selenite 20 concentration of 0.03-0.1 mM was recommended to maintain the balance between mycelium 21 production and Se enrichment. F. velutipes was capable of reducing selenite to elemental Se [Se(0)] including Se(0) nanoparticles, possibly as a detoxification mechanism. This process depended on both selenite concentration and metabolism activity. Overall, the data obtained provided some basic information for the Abstract: Recently, selenium (Se) enriched mushrooms have been exploited as diary Se 29 supplements, but our knowledge of the metabolism process during the Se enrichment process is 30 far from complete. In this study, the uptake, tolerance and reduction of selenite in a widely 31 cultivated mushroom, Flammulina velutipes , was investigated. The results showed that pH 32 variation (from 5.5 to 7.5), metabolic inhibitor (0.1 mM 2,4-DNP) and P or S starvation led to 11%-33 26% decreases in the selenite uptake rate of F. velutipes . This indicates that a minor portion of 34 the selenite uptake was metabolism dependent, whereas a carrier-facilitated passive transport 35 may be crucial. Growth inhibition of F. velutipes initiated at 0.1 mM selenite (11% decrease in 36 the growth rate) and complete growth inhibition occurred at 3 mM selenite. A selenite 37 concentration of 0.03-0.1 mM was recommended to maintain the balance between mycelium 38 production and Se enrichment. F. velutipes was capable of reducing selenite to elemental Se 39 [Se(0)] including Se(0) nanoparticles, possibly as a detoxification mechanism. This process 40 depended on both selenite concentration and metabolism activity. Overall, the data obtained 41 provided some basic information for the cultivation of the selenized F. velutipes , and highlighted 42 the opportunity of using mushrooms for the production of Se(0) nanoparticles.