Mycoremediation

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Pleurotus ostreatus (Oyster mushroom)

Mycoremediation (from

leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products, pesticides and herbicides[2]
in land, fresh water, and marine environments.

The byproducts of the remediation can be valuable materials themselves, such as enzymes (like laccase),[3] edible or medicinal mushrooms,[4] making the remediation process even more profitable. Some fungi are useful in the biodegradation of contaminants in extremely cold or radioactive environments where traditional remediation methods prove too costly or are unusable.

Pollutants

Fungi, thanks to their non-specific enzymes, are able to break down many kinds of substances including pharmaceuticals and fragrances that are normally recalcitrant to bacteria degradation,

distillery wastewater,[7] X-ray contrast agents, and ingredients of personal care products,[8]
can be broken down in a non-toxic way.

Mycoremediation is a cheaper method of remediation, and it doesn't usually require expensive equipment. For this reason, it is often used in small scale applications, such as

mycofiltration of domestic wastewater,[9] and industrial effluent filtration.[10]

According to a 2015 study, mycoremediation can even help with the polycyclic aromatic hydrocarbons (PAH) soil biodegradation. Soils soaked with creosote contain high concentrations of PAH and in order to stop the spread, mycoremediation has proven to be the most successful strategy.[11]

Acid mine drainage from a metallic sulfide mine

Metals

Pollution from metals is very common, as they are used in many industrial processes such as

textiles,[12] paint and leather. The wastewater from these industries is often used for agricultural purposes, so besides the immediate damage to the ecosystem it is spilled into, the metals can enter creatures and humans far away through the food chain. Mycoremediation is one of the cheapest, most effective and environmental-friendly solutions to this problem.[13]
Many fungi are
populations that have been exposed to contaminants for a long time, and have developed a high tolerance. Hyperaccumulation occurs via biosorption on the cellular surface, where the metals enter the mycelium passively with very little intracellular uptake.[14]
A variety of fungi, such as
marine environments, wastewater and on land.[15][16][17][18][19][20][21][22]

Not all the individuals of a species are effective in the same way in the accumulation of toxins. The single individuals are usually selected from an older polluted environment, such as sludge or wastewater, where they had time to adapt to the circumstances, and the selection is carried on in the laboratory[citation needed]. A dilution of the water can drastically improve the ability of biosorption of the fungi.[23]

Coprinus comatus (Shaggy ink cap)

The capacity of certain fungi to extract metals from the ground also can be useful for bioindicator purposes, and can be a problem when the mushroom is of an edible variety. For example, the shaggy ink cap (Coprinus comatus), a common edible mushroom found in the Northern Hemisphere, can be a very good bioindicator of mercury.[24] However, as the shaggy ink cap accumulates mercury in its body, it can be toxic to the consumer.[24]

The capacity of metals uptake of mushroom has also been used to recover precious metals from medium. For example,

mycofiltration techniques.[25]

Organic pollutants

Deepwater Horizon oil spill site with visible oil slicks

Fungi are amongst the primary

intracellular enzymes, especially the cytochrome P450.[28][29]

Other toxins fungi are able to degrade into harmless compounds include

petroleum fuels,[30] phenols in wastewater,[31] polychlorinated biphenyl (PCB) in contaminated soils using Pleurotus ostreatus,[32] polyurethane in aerobic and anaerobic conditions,[33] such as conditions at the bottom of landfills using two species of the Ecuadorian fungus Pestalotiopsis,[34] and more.[35]

Pleurotus pulmonarius mushroom on the side of a tree
Pleurotus pulmonarius

The mechanisms of degradation are not always clear,[36] as the mushroom may be a precursor to subsequent microbial activity rather than individually effective in the removal of pollutants.[37]

Pesticides

Pesticide contamination can be long-term and have a significant impact on decomposition processes and nutrient cycling.[38] Therefore, their degradation can be expensive and difficult. The most commonly used fungi for helping in the degradation of such substances are white rot fungi, which, thanks to their extracellular

ortho-phenylphenol, diphenylamine, chlorpyrifos[40] in wastewater, and atrazine in clay-loamy soils.[41]

Dyes

azo dyes, carcinogenic or otherwise toxic.[42]

The mechanism by which the fungi degrade dyes is via their lignolytic enzymes, especially laccase, therefore white rot mushrooms are the most commonly used.[citation needed]

Mycoremediation has proven to be a cheap and effective remediation technology for dyes such as

direct blue 14 (using Pleurotus).[45]

Synergy with phytoremediation

Phytoremediation is the use of plant-based technologies to decontaminate an area.

Most land plants can form a symbiotic relationship with fungi which is advantageous for both organisms. This relationship is called mycorrhiza. Researchers found that phytoremediation is enhanced by mycorrhizae.[46] Mycorrhizal fungi's symbiotic relationships with plant roots help with the uptake of nutrients and the plant's ability to resist biotic and abiotic stress factors such as heavy metals bioavailable in the rhizosphere. Arbuscular mycorrhizal fungi (AMF) produce proteins that bind heavy metals and thereby decrease their bioavailability.[47][48] The removal of soil contaminants by mycorrhizal fungi is called mycorrhizoremediation.[49]

Mycorrhizal fungi, especially AMF, can greatly improve the phytoremediation capacity of some plants. This is mostly due to the stress the plants suffer because of the pollutants is greatly reduced in the presence of AMF, so they can grow more and produce more biomass.[50][48] The fungi also provide more nutrition, especially phosphorus, and promote the overall health of the plants. The mycelium's quick expansion can also greatly extend the rhizosphere influence zone (hyphosphere), providing the plant with access to more nutrients and contaminants.[51] Increasing the rhizosphere overall health also means a rise in the bacteria population, which can also contribute to the bioremediation process.[52]

This relationship has been proven useful with many pollutants, such as Rhizophagus intraradices and Robinia pseudoacacia in lead contaminated soil,[53] Rhizophagus intraradices with Glomus versiforme inoculated into vetiver grass for lead removal,[54] AMF and Calendula officinalis in cadmium and lead contaminated soil,[55] and in general was effective in increasing the plant bioremediation capacity for metals,[56][57] petroleum fuels,[58][59] and PAHs.[52] In wetlands AMF greatly promote the biodegradation of organic pollutants like benzene-, methyl tert-butyl ether- and ammonia from groundwater when inoculated into Phragmites australis.[60]

Viability in extreme environments

Antarctic fungi species such as Metschnikowia sp., Cryptococcus gilvescens, Cryptococcus victoriae, Pichia caribbica and Leucosporidium creatinivorum can withstand extreme cold and still provide efficient biodegradation of contaminants.[61] Due to the nature of colder, remote environments like Antarctica, usual methods of contaminant remediation, such as the physical removal of contaminated media, can prove costly.[62][63] Most species of psychrophilic Antarctic fungi are resistant to the decreased levels of ATP (adenosine triphosphate) production causing reduced energy availability,[64] decreased levels of oxygen due to the low permeability of frozen soil, and nutrient transportation disruption caused by freeze-thaw cycles.[65] These species of fungi are able to assimilate and degrade compounds such as phenols, n-Hexadecane, toluene, and polycyclic aromatic hydrocarbons in these harsh conditions.[66][61] These compounds are found in crude oil and refined petroleum.

Some fungi species, like Rhodotorula taiwanensis, are resistant to the extremely low pH (acidic) and radioactive medium found in radioactive waste and can successfully grow in these conditions, unlike most other organisms.[67] They can also thrive in the presence of high concentrations of mercury and chromium.[67] Fungi such as Rhodotorula taiwanensis can possibly be used in the bioremediation of radioactive waste due to their low pH and radiation resistant properties.[67] Certain species of fungi are able to absorb and retain radionuclides such as 137Cs, 121Sr, 152Eu, 239Pu and 241Am.[68][10] In fact, cell walls of some species of dead fungi can be used as a filter that can adsorb heavy metals and radionuclides present in industrial effluents, preventing them from being released into the environment.[10]

Fire management

Mycoremediation can even be used for fire management with the encapsulation method. This process consists of using fungal spores coated with agarose in a pellet form, which is introduced to a substrate in the burnt forest, breaking down toxins and stimulating growth.[69]

See also

References

  1. PMID 24949264
    .
  2. PMID 27407289
    .
  3. S2CID 11776284
    . Trametes pubescens MB 89 greatly improved the quality of a wastewater known for toxicity towards biological treatment systems, while simultaneously producing an industrially relevant enzyme.
  4. PMID 24949264
    . The cultivation of edible mushroom on agricultural and industrial wastes may thus be a value added process capable of converting these discharges, which are otherwise considered to be wastes, into foods and feeds
  5. S2CID 24676340
    . municipal wastewater contains small concentrations of the ingredients of many consumer products and drugs. Many of these contaminants do not lend themselves to bacterial degradation because of distinctly xenobiotic structures.
  6. PMID 27647241
    .
  7. S2CID 11776284
    . Trametes pubescens MB 89 greatly improved the quality of a wastewater known for toxicity towards biological treatment systems
  8. S2CID 24676340
    . ligninolytic basidiomycetes and mitosporic ascomycetes, including aquatic fungi, are known to degrade EDCs (nonylphenol, bisphenol A and 17α-ethinylestradiol); analgesic, anti-epileptic and non-steroidal anti-inflammatory drugs; X-ray contrast agents; polycyclic musk fragrances; and ingredients of personal care products
  9. S2CID 23689795
    . Within 2-3 days of treatment application, encouraging results were achieved in total dry solids (TDS), total suspended solid (TSS), turbidity, chemical oxygen demand (COD), specific resistance to filtration (SRF), and pH due to fungal treatment in recognition of bioseparation and dewaterability of wastewater sludge compared to control.
  10. ^ a b c Belozerskaya, T.; Aslanidi, K.; Ivanova, A.; Gessler, N.; Egorova, A.; Karpenko, Y.; Olishevskaya, S. (2010). "Characteristics of Extremophylic Fungi from Chernobyl Nuclear Power Plant". Current Research, Technology and Education Topics in Applied Microbiology and Microbial Biotechnology: 88–94 – via ResearchGate.
  11. PMID 25506817
    .
  12. S2CID 103499429
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  13. PMID 23024411
    . Wastewater particularly from electroplating, paint, leather, metal and tanning industries contain enormous amount of heavy metals. Microorganisms including fungi have been reported to exclude heavy metals from wastewater through bioaccumulation and biosorption at low cost and in eco-friendly way.
  14. S2CID 14253113
    . The sequestration of the metal occurred mainly by sorption to the cell-surface with very little intracellular uptake.
  15. ^
    S2CID 14253113
    . Selected cultures displayed a good sorption capacity of 32 - 41 mg Pb2+ and 3.5 - 6.5 mg Cu2+ g-1 dry weight of mycelia
  16. ^
    PMID 23024411
    .
  17. ^
    S2CID 22294536
    . This latter [Trichoderma harzianum strain] hyperaccumulates up to 11,000 mg Ni kg-1, suggesting its possible use in a bioremediation protocol able to provide a sustainable reclamation of broad contaminated areas.
  18. ^
    PMID 25079829
    . The strain was able to remove 97.50% and 98.73% mercury from shaken and static systems respectively. A. flavus strain KRP1 seems to have potential use in bioremediation of aqueous substrates containing mercury(II) through a biosorption mechanism.
  19. ^
    PMID 26348882
    . These fungal strains [Aspergillus oryzae FNBR_L35; Fusarium sp. FNBR_B7, FNBR_LK5 and FNBR_B3; Aspergillus nidulans FNBR_LK1; Rhizomucor variabilis sp. FNBR_B9; and Emericella sp. FNBR_BA5] can be used for As remediation in As-contaminated agricultural soils.
  20. ^
    PMID 25240213
    .
  21. ^
    S2CID 37796594
    . The maximum boron removal yield by P. crustosum was 45.68% at 33.95 mg l(-1) initial boron concentration in MSM, and was 38.97% at 42.76 mg l(-1) boron for R. mucilaginosa, which seemed to offer an economically feasible method of removing boron from the effluents.
  22. ^
    PMID 28704692
    . Efficiency of Pleurotus for remediation of heavy metals was found to be highest in the 50% diluted effluent (57.2% Mn, 82.6% Zn, 98.0% Ni, 99.9% Cu, 99.3% Co, 99.1% Cr, 89.2% Fe and 35.6% Pb)
  23. PMID 28704692
    .
  24. ^
    PMID 26705753
    . Eating them when foraged from the urban places can provide to a consumer Hg at relatively high dose, while unresolved question is absorption rate of Hg compounds contained in ingested mushroom meal.
  25. doi:10.1002/aic.14917
    .
  26. PMID 28499155
    . The levels of adsorption of the phenolic and PAHs were negligible with 99% biodegradation being observed in the case of benzo-α-pyrene, phenol and p-chlorophenol
  27. PMID 21040933
    . The fungus Aspergillus sclerotiorum CBMAI 849 showed the best performance with regard to pyrene (99.7%) and benzo[a]pyrene (76.6%) depletion after 8 and 16 days, respectively. [...] Because these fungi were adapted to the marine environment, the strains that were used in the present study are considered to be attractive targets for the bioremediation of saline environments, such as ocean and marine sediments that are contaminated by PAHs.
  28. PMID 27407289
    . certain fungi possess intracellular networks which constitute the xenome, consisting of cytochrome (CYP) P450 monooxygenases and the glutathione transferases for dealing with diverse range of pollutants.
  29. PMID 22830035
    . Ligninolytic fungi, such as Phanerochaete chrysosporium, Bjerkandera adusta, and Pleurotus ostreatus, have the capacity of PAH degradation. The enzymes involved in the degradation of PAHs are ligninolytic and include lignin peroxidase, versatile peroxidase, Mn-peroxidase, and laccase.
  30. PMID 26111162
    . Averaging across all studied species, 98.1%, 48.6%, and 76.4% of the initial Bunker C C10 alkane, C14 alkane, and phenanthrene, respectively were degraded after 180 days of fungal growth on pine media.
  31. PMID 28499155
    . When this wastewater was supplemented with 0.1 mM glucose, all of the tested fungi, apart from A. caesiellus, displayed the capacity to remove both the phenolic and PAH compounds
  32. PMID 27894756
    . The best results were obtained with P. ostreatus, which resulted in PCB removals of 18.5, 41.3 and 50.5% from the bulk, top (surface) and rhizosphere, respectively, of dumpsite soils after 12 weeks of treatment
  33. ^ "Could Plastic-Eating Mushrooms Solve mankind's Plastic Problem?". Sciencemint. 2021-04-14. Archived from the original on 2021-04-14. Retrieved 2021-07-02.
  34. PMID 21764951
    .
  35. S2CID 24676340
    . species of the genera Cladophialophora and Exophiala (of the order Chaetothyriales) assimilate toluene. Aspergillus and Penicillium spp. (of the order Eurotiales) degrade aliphatic hydrocarbons, chlorophenols, polycyclic aromatic hydrocarbons (PAhs), pesticides, synthetic dyes and 2,4,6-trinitrotoluene (TnT). metabolization of polychlorinated dibenzo-p-dioxins (PCDDs) is reported for the genera Cordyceps and Fusarium (of the order hypocreales), as well as for Pseudallescheria spp. (of the order microascales). The mitosporic Acremonium spp. degrade PAhs and Royal Demolition Explosive (RDX), and Graphium spp. degrade methyl-tert-butylether (mTBE). outside of the Pezizomycotina, Phoma spp. degrade PAhs, pesticides and synthetic dyes. The subphylum Saccharomycotina mostly consists of yeasts and includes degraders of n-alkanes, n-alkylbenzenes, crude oil, the endocrine disrupting chemical (EDC) nonylphenol, PAhs and TnT (in the genera Candida, Kluyveromyces, Neurospora, Pichia, Saccharomyces and Yarrowia
  36. PMID 26111162
    . The mechanisms by which P. strigosozonata may degrade complex oil compounds remain obscure, but degradation results of the 180-day cultures suggest that diverse white-rot fungi have promise for bioremediation of petroleum fuels.
  37. PMID 27894756
    . P. ostreatus efficiently colonized the soil samples and suppressed other fungal genera. However, the same fungus substantially stimulated bacterial taxa that encompass putative PCB degraders.
  38. PMID 23956663
    .
  39. PMID 23022115
    . the basidiomycete Bjerkandera adusta was able to degrade 83% of (alpha+beta) endosulfan after 27 days, 6 mg kg(-1) of endosulfan diol were determined; endosulfan ether and endosulfan sulfate were produced below 1 mg kg(-1) (LOQ, limit of quantitation).
  40. S2CID 23746146
    .
  41. S2CID 23973026
    . This study demonstrated that both the monoculture extracts of the native strain T. maxima and its co-culture with P. carneus can efficiently and quickly degrade atrazine in clay-loam soils.
  42. PMID 27532013
    .
  43. PMID 25477943
    . Aspergillus niger recorded maximum decolorization of the dye Basic fuchsin (81.85%) followed by Nigrosin (77.47%), Malachite green (72.77%) and dye mixture (33.08%) under shaking condition. Whereas, P. chrysosporium recorded decolorization to the maximum with the Nigrosin (90.15%) followed by Basic fuchsin (89.8%), Malachite green (83.25%) and mixture (78.4%).
  44. PMID 24031787
    . the decolourisation obtained at optimized conditions varied between 29.25- 97.28% at static condition and 82.1- 100% at shaking condition
  45. PMID 23841054
    .
  46. doi:10.1016/bs.abr.2016.12.005
  47. S2CID 249970822
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  48. ^
    S2CID 224927111
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  49. PMID 16773723
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  50. PMID 24049473
    . As consequence of the treatment with Am [Arbuscolar mycorrhize], the plants provide a greater sink for the contaminants since they are better able to survive and grow.
  51. PMID 27487095
    . AMF have been considered to be a tool to enhance phytoremediation, as their mycelium create a widespread underground network that acts as a bridge between plant roots, soil and rhizosphere microorganisms. Abundant extramatrical hyphae extend the rhizosphere thus creating the hyphosphere, which significantly increases the area of a plant's access to nutrients and contaminants.
  52. ^
    PMID 24049473
    . Highly significant positive correlations were shown between of arbuscular formation in root segments (A)) and plant water content, root lipids, peroxidase, catalase polyphenol oxidase and total microbial count in soil rhizosphere as well as PAH dissipation in spiked soil.
  53. PMID 26842958
    . Non-mycorrhizal legumes were more sensitive to Pb addition than that of mycorrhizal legumes [...] The presence of AMF greatly increased the total biomass of legumes in all treatments
  54. S2CID 24134740
    . With mycorrhizal inoculation and increasing Pb levels, Pb uptake of shoot and root increased compared to those of NM control
  55. S2CID 38602727
    . However, mycorrhizal fungi alleviated these impacts by improving plant growth and yield. Pot marigold concentrated high amounts of Pb and especially Cd in its roots and shoots; mycorrhizal plants had a greater accumulation of these metals, so that those under 80 mg/kg Cd soil(-1) accumulated 833.3 and 1585.8 mg Cd in their shoots and roots, respectively.
  56. S2CID 24501499
    . Redundancy analysis (RDA) showed that the efficiency of phytoremediation was enhanced by AM symbioses, and soil pH, Pb, Zn, and Cd levels were the main factors influencing the HM accumulation characteristics of plants.
  57. PMID 24455959
    . Population of microorganism increased obviously. All the above results show that their ecological effects are significantly improved. AM would promote rhizosphere soil that will help the sustainability of ecological systems in mining area.
  58. S2CID 22961287
    . the degradation rate of total petroleum hydrocarbon during treatment with PGPR and AMF in moderately contaminated soil reached a maximum of 49.73%
  59. PMID 21420227
    . AMF-plants significantly contributed in higher degradation of total petroleum hydrocarbons when compared to non-AMF-plants.
  60. PMID 22846140
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  61. ^
    S2CID 199887141
  62. ISBN 978-3-540-69371-0
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