Location: Water Management ResearchTitle: Integrating Phytoextraction and Biofortification: Fungal Accumulation of Selenium in Plant Materials from Phytoremediation of Agricultural Drainage) Author
Submitted to: Proceedings of US EPA Silesia Soil Remediation Workshop
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2009
Publication Date: 8/5/2009
Citation: Hong, I.,G.S. Banuelos,Z.Q. Lin. 2009.Integrating Phytoremediation and biofortification:Use of Se-laden Plant materials for Production of Se-enriched Edible Mushrooms.6th Phytotechnology on soil Remediation,St. Louis, EPA Press. pp.77-79. Interpretive Summary: Selenium (Se) is a natural-occurring element in the Westside of central California. The presence of Se in drainage water has been a major environmental concern for irrigated agriculture in this region for the last 20 years. Several plant species, e.g., Indian mustard, pickleweed, and other salt/Se tolerant species, have been identified to be effective for extracting Se in central California. However, the disposal of Se laden plant materials produced from vegetation management is challenging. One strategy under consideration is to utilize the harvested plant material as a source of organic Se for growing mushrooms. Because fungi are decomposers in biogeochemical cycling of Se, Se in growth media could be bioaccumulated, and volatilized by fungi. Thus, we examined the ability of selected edible mushrooms to accumulate and volatilize Se from Se-enriched plant material that was harvested from a phytoremediation site. Volatilization of Se was greatest during the first 24 hours, and Se was accumulated by the fungi. This short term study demonstrates that fungi (mushrooms) have the ability to accumulate Se from Se-laden plant residues, while generating a new product; Se-enriched mushrooms. Growing edible mushrooms in Se-laden plant materials harvested from Se rich soils may provide a new valuable source of Se supplement for humans.
Technical Abstract: The phytomanagement of Se-polluted soil and water is one strategy that may be environmentally sustainable and cost-effective for soils and waters enriched with natural-occurring Se. Several plant species, including Indian mustard (Brassica juncea), pickleweed (Salicornia bigelovii), and other salt/Se tolerant species, have been identified to be effective for phytoextraction of Se from soils in the westside of Central California. However, the management or disposal of Se-laden plant materials harvested from such sites is still being investigated. Because fungi are decomposers in biogeochemical cycling, Se in growth media could be bioaccumulated and volatilized by fungi. In addition to slowly reducing total Se mass present in Se-enriched plant residues by planting fungi into a Se-rich medium, we may generate new agricultural products, such as Se-enriched mushrooms. Thus, the objectives of this study were to (1) determine the capacity of selected edible mushrooms to accumulate Se from different sources of Se, (2) measure the effects of different chemical forms of Se in substrates on Se accumulation in fungal tissues, and (3) quantify the significance of fungal volatilization of Se in the decomposition process. Four laboratory experiments were carried out to achieve the objectives: (1) Pearl oyster mushrooms (Pleurotus ostreatus) were grown in the sawdust substrate treated with 0, 2, 4, and 8 mg kg-1 of selenate from Na2SeO4. Na2SeO3 (selenite), or C5H11NO2Se (selenomethionine or SeMet) at a concentration of 3 mg/kg, or mixed with Se-laden Rio creeping wildrye grass (Leymus triticoides) that was collected from a phytoremediation field site in Central California. Enokitake mushrooms (Flammulina populicola) were treated with 3 mg kg-1 of Se as selenate, selenite, or SeMet, respectively. The treated mushrooms were immediately enclosed in flow-through chambers for Se volatilization measurement, and analyzed for Se after 8 days of growth in the Se-substrate. The total amount of Se accumulated in oyster mushroom tissues increased with increasing concentrations of Se in the substrate. The highest Se concentration in pearl oyster mushroom tissues was 65'7 mg Se/kg DM in the substrate treated with 8 mg Se/kg DM from selenate. The accumulation of Se in both oyster mushroom and Enokitake mushroom tissues was affected by the chemical form of Se supplied in the substrates; however, different mushroom species responded differently. SeMet was accumulated the most in Enokitake tissues, followed by selenite and then selenate, while Oyster mushroom accumulated more Se from selenate, SeMet, and from the creeping wildrye grass, but less from selenite. Organic Se (SeMet) was volatilized more rapidly compared to inorganic selenite and selenate. The rate of Se volatilization was highest during the first 24 hours immediately after Se was supplied to the substrate, and ranged from 1406±952 to 227±128 ng Se per jar per day, during the 8-day experimental period. Growing edible mushrooms in different sources of Se and in Se-laden plant materials may provide a valuable source of Se supplement for humans.