Mycoremediation of Heavy Metals

Use of soil fungi in the biosorption of three trace metals (Cd, Cu, Pb): promising candidates for treatment technology?

Trace metal contamination is a widespread and complex environmental problem. Because fungi are capable of growing in adverse environments, several fungal species could have an interesting potential in remediation technologies for metal contaminated environments. This study proposes to test the ability to tolerate and biosorb three trace metals (Cd, Cu and Pb) of 28 fungal isolates collected from different soils. First, a tolerance assay in agar medium was performed. Each isolate was grown in the presence of Cd, Cu, and Pb at different concentrations. Then, we exposed each soil fungus to 50 mg L^-1 of Cd, Cu, or Pb during 3 days in liquid medium. Parameters such as biomass production, pH, and biosorption were evaluated. The results showed that responses to metal exposure are very diverse even with fungi isolated from the same soil sample, or belonging to the same genera. Several isolates could be considered as good metal biosorbents and could be used in future mycoremediation studies. Among the 28 fungi tested, Absidia cylindrospora biosorbed more than 45% of Cd and Pb, Chaetomium atrobrunneum biosorbed more than 45% of Cd, Cu, Pb, and Coprinellus micaceus biosorbed 100% of Pb.

Removal of Pb (II), As (III), and Cr (VI) by nitrogen-starved Papiliotrema laurentii strain RY1

Heavy metals such as lead, chromium, and metalloid like arsenic dominate the pinnacle in posing a threat to life. Being environment-friendly, elucidating the mechanism by which microorganisms detoxify such elements has always been an active field of research hitherto. In the present study, we have investigated the capability of nitrogen-deprived Papiliotrema laurentii strain RY1 toward enhanced tolerance and neutralizing toxic elements. There were biosorption and bioprecipitation of lead and chromium at the cell surfaces. Bioprecipitation mechanisms included the formation of lead phosphates and pyromorphites from lead, grimaldite from chromium. Transcripts such as metallothionein, aquaporins, and arsenical pump-driving ATPase have been surmised to be involved in the detoxification of elements. Furthermore, activation of antioxidant defense mechanisms for the cells for each of the elements should contribute towards yeast's propagation. The efficiency of removal of elements for live cells and immobilized cells were high for lead and chromium. To the best of our knowledge, this is the first report of such high tolerance of lead, arsenic, and chromium for any yeast. The yeast showed such varied response under dual stress due to nitrogen starvation and in the presence of respective elements. The yeast possesses promising potentials in nitrogen deprived and enriched environments to aid in bioremediation sectors.

Detoxification of textile effluent by fungal treatment and its performance in agronomic usages

Globally, scarcity of contaminant free water usages is increasing gradually; it might be solved after generation of any sustainable technology to detoxify contaminated waters. An attempt was undertaken to detoxify textile effluent with fungal strains Trichoderma harzianum and Mucor hiemalis. Fungal detoxified effluent and its performance on three crops (wheat, mungbean, and mustard) seed germination in petri dishes and seedlings establishment of mustard in polythene bag were evaluated. Fungal strains significantly detoxified textile effluent by removal of 76% total solids, 91.35% COD, 77.34% absorbance against optical density, and increased 87.31% DO. Studied heavy metals were reduced significantly (P ≤ 0.05) in treated effluent by both fungal strains but superior performance was achieved by Mucor hiemalis. Maximum 92.5, 88.7, 83, and 100% removal of Mn, Zn, Cu, and Fe were monitored in fungal-treated effluent, respectively. Seeds germination and seedling growth by fungal treated effluents were similar and insignificant with the results achieved in tap water but which was significant over raw textile effluent. Eighty and above percent seed germination in petri dishes was recorded at 48 h by Mucor hiemalis-treated textile effluent but conversely at the same period it was below 10% in raw effluent. Significant achievement of seedling establishment was noticed in poly bag with fungal-treated effluent. The applied technique might be a prospective way to detoxify and recycle the industrial effluents for beneficial purpose in the future.