Fungus, white rot

Pleurotus ostreatus (Jacq.) P. Kumm.

Oyster mushroom

An industrially cultivated white-rot fungus and the species most often used in soil mycoremediation studies: it colonises non-sterile soil from a lignocellulosic carrier and attacks high-molecular-weight PAHs and PCBs that the resident microflora degrades poorly. It is one of the few fungi with a documented field pilot on creosote-contaminated soil.

Thomas Pruß, CC BY-SA 3.0

How it works

Mechanisms: mycodegradation
Enzymes: laccase, manganese peroxidase

Contaminants

Contaminant	Evidence	What was shown
Creosote	field	Wood-preserving site in West Virginia (USA): in the field pilot, with P. ostreatus grown on two local substrate mixtures, total PAHs fell by up to 93.2% in 276 days; all individual PAHs but one reached industrial risk-based concentrations. In the preceding bench treatability test the reduction was up to 67.3% in 56 days. Lamar, White & Ashley (2002) Evaluation of white-rot fungi for the remediation of creosote-contaminated soil. Remediation Journal 12:97-106, 2002
Polycyclic aromatic hydrocarbons	laboratory	Non-sterile soil, 15 weeks: degradation of 4-6-ring PAHs (benzo[a]anthracene, chrysene, benzo[b]- and benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[ghi]perylene), with 16-69% of individual compounds recovered at the end; the fungus mainly enhanced the disappearance of 5-6-ring compounds. In creosote soil (50-200 mg/kg PAH) at 15 °C for 120 days removal was 55-67%: 86-96% for 2-ring and 31-38% for 5-6-ring PAHs. Baldrian et al. (2000) Influence of cadmium and mercury on activities of ligninolytic enzymes and degradation of PAHs by Pleurotus ostreatus in soil. Appl Environ Microbiol 66:2471-2478, 2000 Byss et al. (2008) Fungal bioremediation of the creosote-contaminated soil. Chemosphere 73:1518-1523, 2008 Covino et al. (2010) Inoculum carrier and contaminant bioavailability affect fungal degradation performances of PAH-contaminated solid matrices from a wood preservation plant. Chemosphere 79:855-864, 2010
Polychlorinated biphenyls	laboratory	Long-term PCB-contaminated dumpsite soils, 12-week microcosms: 18.5%, 41.3% and 50.5% removal from bulk, surface and rhizosphere soil respectively. Hydroxylated and methoxylated PCBs, chlorobenzoates and chlorobenzyl alcohols were identified, showing that the aromatic ring is oxidised and cleaved. Stella et al. (2017) Bioremediation of long-term PCB-contaminated soil by white-rot fungi. J Hazard Mater 324:701-710, 2017

Contaminant

Evidence

What was shown

Creosote

field

Wood-preserving site in West Virginia (USA): in the field pilot, with P. ostreatus grown on two local substrate mixtures, total PAHs fell by up to 93.2% in 276 days; all individual PAHs but one reached industrial risk-based concentrations. In the preceding bench treatability test the reduction was up to 67.3% in 56 days.

Lamar, White & Ashley (2002) Evaluation of white-rot fungi for the remediation of creosote-contaminated soil. Remediation Journal 12:97-106, 2002

Polycyclic aromatic hydrocarbons

laboratory

Non-sterile soil, 15 weeks: degradation of 4-6-ring PAHs (benzo[a]anthracene, chrysene, benzo[b]- and benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[ghi]perylene), with 16-69% of individual compounds recovered at the end; the fungus mainly enhanced the disappearance of 5-6-ring compounds. In creosote soil (50-200 mg/kg PAH) at 15 °C for 120 days removal was 55-67%: 86-96% for 2-ring and 31-38% for 5-6-ring PAHs.

Polychlorinated biphenyls

laboratory

Long-term PCB-contaminated dumpsite soils, 12-week microcosms: 18.5%, 41.3% and 50.5% removal from bulk, surface and rhizosphere soil respectively. Hydroxylated and methoxylated PCBs, chlorobenzoates and chlorobenzyl alcohols were identified, showing that the aromatic ring is oxidised and cleaved.

Stella et al. (2017) Bioremediation of long-term PCB-contaminated soil by white-rot fungi. J Hazard Mater 324:701-710, 2017

Limits

Degradation tracks bioavailability: in aged PAH contamination only a few compounds are removed beyond their bioavailable fraction (Covino et al. 2010). The fungus needs a lignocellulosic carrier (straw, pellets, corn cobs) and does not persist in soil without it. Cd at 500 ppm cancels the fungal contribution, and Hg at 50-100 ppm or Cd at 100-500 ppm limits soil colonisation (Baldrian et al. 2000). PCB removal ranges from 18 to 50% depending on the soil. Published field trials are few and at pilot scale.

Where it has been tried

Canale dei Navicelli, sedimenti di dragaggio

MycoremediationLaboratory, with soil from the site

Lambertella sp. MUT 5852, Pleurotus ostreatus

The University of Pisa (Becarelli, Siracusa, Di Gregorio and colleagues) isolated from the sediments four ascomycetes able to degrade diesel. The Lambertella strain was added to the sediments co-composted with lignocellulosic residues; a later study compared it with co-composting on spent Pleurotus ostreatus substrate.

Outcome With Lambertella 47.6% of total hydrocarbons were degraded in two months. In the later comparison adding the strain proved necessary to bring hydrocarbons down: spent Pleurotus substrate alone was not enough.

Petroleum hydrocarbons

Czech Republic, wood-preserving plant (creosote soil)

MycoremediationLaboratory, with soil from the site

Pleurotus ostreatus, Irpex lacteus

Byss, Elhottová, Tříska and Baldrian incubated the soil with the two fungi at 15 °C for 120 days, following PAHs and the microbial community.

Outcome Pleurotus ostreatus removed 55–67% of PAHs, Irpex lacteus 27–36%. By class: 86–96% (Pleurotus) and 47–59% (Irpex) of 2-ring compounds, but only 31–38% and 11–13% of 5–6-ring ones. Both fungi lowered bacterial biomass. It is a laboratory trial.

Polycyclic aromatic hydrocarbons

Byss et al., Fungal bioremediation of the creosote-contaminated soil: influence of Pleurotus ostreatus and Irpex lacteus on polycyclic aromatic hydrocarbons removal and soil microbial community composition in the laboratory-scale study, Chemosphere, 2008

Ringe (former coal-tar storage) and B&W shipyard soils

MycoremediationField pilot

Pleurotus ostreatus

Hestbjerg, Willumsen, Christensen, Andersen and Jacobsen mixed into the soils the refuse substrate of commercial Pleurotus ostreatus production, outdoors, in concrete cylinders (50 cm × 60 cm) in triplicate, with controls without additions and with autoclaved sawdust; 21 PAHs measured.

Outcome In the Ringe soil, after nine weeks, 3-ring PAHs had fallen by 78% and 4-ring ones by 41%, while 5–6-ring ones by only 4%. The reduction went with high initial laccase activity and a rise in degrading bacteria. The heaviest compounds, the most toxic, were left almost untouched.

Polycyclic aromatic hydrocarbons

Hestbjerg et al., Bioaugmentation of tar-contaminated soils under field conditions using Pleurotus ostreatus refuse from commercial mushroom production, Environmental Toxicology and Chemistry, 2003

Santa Cruz Mountains, CZU Lightning Complex burn area

MycoremediationField pilot, 2021–

Pleurotus ostreatus

The non-profit CoRenewal laid straw wattles inoculated with Pleurotus mycelium (a local strain supplied by Far West Fungi) along the slopes below burnt houses, with uninoculated wattles as controls, and took baseline samples above and below the wattles.

Outcome No measured result in the source consulted (May 2021): the group planned to resample after one or two years. The effectiveness of inoculated wattles after wildfires is still to be shown.