Fungal biomass provides a metal sink, either by metal biosorption to biomass (cell walls, pigments, and extracellular polysaccharides), intracellular accumulation, and sequestration, or by precipitation of metal compounds onto and/or around hyphae. Fungi are effective biosorbents for a variety of metals, including Ni, Zn, Ag, Cu, Cd, and Pb and this can be an important passive process in both living and dead biomass. The presence ofchitin, and pigments like melanin, strongly influences the ability of fungi to act as sorbents. In a biotechnological context, fungi and their byproducts have received considerable attention as biosorbent materials for metals and radionuclides.
Fungi can precipitate several inorganic and organic compounds, for example, oxalates, oxides, and carbonates and this can lead to formation of biogenic minerals (myco-genic precipitates) as discussed previously. Precipitation, including crystallization, immobilizes metals but also leads to release of nutrients like sulfate and phosphate.
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