Metal sorption by biomass of melanin‐producing fungi grown in clay‐containing medium

Abstract

The sorption of toxic metals by fungal mycelia grown in clay-containing medium is reported in this work. Biomass of melanin-producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay-containing medium were compared for their equilibrium Cu and Cd uptake from pHbuffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal-binding ability of the fungal-clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Q max ) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay-containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the 'biomineral' association.

Enhanced Tolerance to Cadmium in Bacterial-Fungal Co-Cultures as a Strategy for Metal Biorecovery from e-Waste

“…B. exigua, showed a strong melanization in these conditions. Melanization in fungi is a typical stress response [76] and, has been mentioned to be involved in metal biosorption as a strategy to immobilize toxic metals [77,78]. All four strains of the two BFI couples were confirmed as urea-positive and no inhibition effect was present in urea-containing media.…”

Metals, minerals and microbes: geomicrobiology and bioremediation

“…Direct biophysical effects have been shown where fungal hyphae attracted and oriented clay platelets because of surface charge phenomena, and acted as nucleation zones for the formation of narrow clay-lined channels (Ritz & Young, 2004). Interactions between clay minerals and microbes alter the adsorptive properties of both clays and biomass (Fomina & Gadd, 2002b). Under certain conditions, the sorption abilities of microbe-clay aggregates can be decreased due to blocking and masking of binding sites or increased due to modification of binding sites and emergence of new ones (Fomina & Gadd, 2002b;Tazaki, 2006).…”

“…Interactions between clay minerals and microbes alter the adsorptive properties of both clays and biomass (Fomina & Gadd, 2002b). Under certain conditions, the sorption abilities of microbe-clay aggregates can be decreased due to blocking and masking of binding sites or increased due to modification of binding sites and emergence of new ones (Fomina & Gadd, 2002b;Tazaki, 2006). As well as being important in stages of mineral soil and sediment formation and development, bioweathering mechanisms also effect structural decay of rock and mineral-based building materials, monuments and other structures.…”

“…Fungal-clay biomineral sorbents combine the sorptive advantages of the individual components, i.e. the high density of metal-binding sites per unit area and high sorption capacity of the fungal biomass, and the high sorption affinity, high surface area per unit weight, mechanical strength and efficient sorption at high metal concentrations of the clay minerals (Fomina & Gadd, 2002b). Saccharomyces cerevisiae mutants (pmr1D) hypersensitive to heavy metals due to increased metal uptake have been investigated for the ability to remove Mn 2+ , Cu 2+ , Co 2+ or Cd 2+ from synthetic effluents by a combination of biosorption and continuous metabolic uptake after physical adsorption (Ruta et al, 2010).…”

The decomposition of ectomycorrhizal fungal necromass

“…Because of its recalcitrance, its requirement for oxidative enzymes for degradation, and the large variation in concentrations across fungal species, melanin in fungal tissues may be analogous to lignin in plant tissues in biochemical control of necromass decomposition. Additionally, melanized hyphae also have higher sorption to soil mineral components compared to hyaline hyphae (Fomina and Gadd, 2003), which may result in physiochemical protection of necromass C, which would also result in increased incorporation into stable SOM (Fernandez and Kennedy, 2015).…”