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White-rot fungi rot wood by attacking lignin with strong oxidizing enzymes released outside the cell. Those enzymes aren’t selective, so the same fungi can also attack stubborn aromatic pollutants such as PAHs and dioxins. In a 2020 study, one white-rot fungus removed 96% of the dioxins and furans from a heavily contaminated field soil in 72 days. The result is real and narrow: a controlled treatment of soil collected from one site, with no bearing on any other site.
What white-rot fungi are
White-rot fungi are wood-decay fungi, among them Phanerochaete chrysosporium, Bjerkandera adusta and Pleurotus ostreatus. Their working enzymes are lignin peroxidase, versatile peroxidase, manganese peroxidase and laccase [1]. Because the enzymes act outside the cell through reactive chemistry, lignin isn’t their only target. A 1985 Science paper reported P. chrysosporium degrading DDT, two PCBs, 2,3,7,8-tetrachlorodibenzo-p-dioxin, lindane and benzo[a]pyrene to carbon dioxide in culture, and tied the ability to the fungus’s extracellular lignin-degrading enzyme system [2].
That lab finding opened the field and explains why the research on these fungi is so large. It says nothing about how they behave in field soil with other microbes, weather and patchy contamination.
What the research shows
| Study | Organism | Contaminant | Setting | What was reported |
|---|---|---|---|---|
| Bumpus et al., 1985 [2] | Phanerochaete chrysosporium | DDT, PCBs, a dioxin, lindane, benzo[a]pyrene | Laboratory culture | Degradation to carbon dioxide, dependent on the extracellular lignin-degrading enzyme system |
| Valli et al., 1992 [3] | P. chrysosporium | 2,7-dichlorodibenzo-p-dioxin | Laboratory culture | A degradation pathway worked out step by step. Lignin peroxidase and manganese peroxidase cleave the dioxin ring and remove both chlorines before the aromatic ring is opened. |
| Pozdnyakova, 2012 review [1] | Several white-rot and litter-decomposing fungi | PAHs | Submerged cultures and mycoremediation of PAH-contaminated soils | Summarizes the role of ligninolytic enzymes in PAH degradation |
| Kaewlaoyoong et al., 2020 [4] | Pleurotus pulmonarius | Dioxins and furans (PCDD/F) | Field soil from a closed pentachlorophenol plant, treated under controlled conditions | 96% overall removal in 72 days |
| Kaewlaoyoong et al., 2021 [5] | P. pulmonarius | PCDD/F | Unsterilized field soil, controlled conditions | About 60% removal in 30 days at a lower starting concentration |
The dioxin study up close
In this study, a white-rot fungus grown on a solid substrate and mixed into dioxin-contaminated soil removed most of the dioxins and furans in a controlled test. That supports the idea that this kind of treatment can work on some dioxin-contaminated soils, and goes no further.
The paper was published by Kaewlaoyoong A, Cheng CY, Lin C, Chen JR, Huang WY and Sriprom P in Science of the Total Environment 738:139670, 2020 [4], and the authors declared no competing interests.
The researchers took unsterilized soil from a long-closed pentachlorophenol plant in southern Taiwan, with total PCDD/F of 14,000 ± 2,400 ng I-TEQ per kilogram, and mixed it with solid fungal inoculum at a dry-weight ratio of 1:1.4 before incubating it at 26 ± 2 °C under controlled conditions [4].
After 72 days the more toxic tetra- and penta-chlorinated dioxins and furans were down to non-detectable levels. Removal of the hexa-, hepta- and octa-chlorinated forms was above 80%, 97% and 90%. Overall removal was 96%, leaving 276 ng I-TEQ per kilogram, below the 1,000 ng I-TEQ per kilogram regulatory control limit the authors cite. Manganese peroxidase activity tracked removal closely (r = 0.88); laccase did not [4]. The authors call the removal nonspecific, since low- and high-chlorinated compounds degraded together [4].
What kind of evidence exists
| Type of study | Present in this literature? |
|---|---|
| Laboratory culture | Yes [2][3] |
| Controlled treatment of a real contaminated soil | Yes, one soil from one site [4][5] |
| Field pilot in place | None cited here |
| Full-scale project | None cited here |
What it doesn’t show
- The study involved no in-place treatment, since the soil was collected and treated at controlled temperature.
- Its results cover one soil from one site, and another soil, climate or congener mix could behave differently.
- The study doesn’t show a clean disposal picture either. The same group’s 2021 follow-up, on unsterilized soil starting at 4,432 ng WHO-TEQ per kilogram, reported about 60% removal in 30 days, attributed to ligninolytic enzymes and to uptake into the fungal fruiting bodies, which held about 110 ng WHO-TEQ per kilogram of mushroom [5]. Fruiting bodies carrying dioxins have to be handled as waste. The follow-up also found chlorinated metabolites and describes a patented incubation approach [5].
- The abstracts don’t address cost, equipment or scale-up.
- It doesn’t apply to any specific incident, because the soil came from one closed plant in Taiwan, and nothing in it supports a claim about another site.
For a decision-maker, the study matters because dioxins and furans are among the hardest contaminants to treat, so a documented biological route for collected soil is useful context when officials weigh options. It doesn’t mean biology will work on a particular site.
PAHs
The PAH research is broader, and the 2012 review covers submerged cultures and mycoremediation of PAH-contaminated soils with ligninolytic fungi [1], and again the details depend on the fungus, the compound and the conditions. Our fit chart puts PAHs in the “partial fit” group for biology overall.
What to expect
- The 96% result came at a steady 26 °C [4], while field temperatures swing.
- Competing microbes make unsterilized soil hard to treat, and the authors describe their method as overcoming a well-known intractability of PCDD/F biodegradation in such soil [4], which is their interpretation of one study.
- Some of the dioxin that disappeared may have gone into fungal tissue as uptake [5].
- Real contamination is a mixture of congeners, and each study reports its own.
Where Elm Dirt fits
This post is about a group of fungi and what researchers have done with them. Elm Dirt’s products carry a broad fungal community: independent lab analysis (Biome Makers) identified 291 microbial species in Plant Juice, 68 of them on the report’s fungal list. For dioxins, our field approach pairs soil biology with biochar and carbon amendments that reduce how much dioxin can move, with results measured by independent lab testing.
Dioxins and furans are one of the compound groups in Elm Dirt’s East Palestine work, where we have product in the ground as part of an ongoing soil-restoration pilot, with independent lab monitoring. Expect months to a year or more for that work, with independent lab testing to confirm it. More on the dioxins and furans page and the pilot program page.
Open question
How white-rot fungi would perform in place on a particular dioxin site is a question for a treatability study. If you have dioxin results, send them to us.
Sources
- Pozdnyakova NN. Involvement of the ligninolytic system of white-rot and litter-decomposing fungi in the degradation of polycyclic aromatic hydrocarbons. Biotechnology Research International 2012:243217. doi:10.1155/2012/243217.
- Bumpus JA, Tien M, Wright D, Aust SD. Oxidation of persistent environmental pollutants by a white rot fungus. Science 228(4706):1434-1436, 1985. doi:10.1126/science.3925550.
- Valli K, Wariishi H, Gold MH. Degradation of 2,7-dichlorodibenzo-p-dioxin by the lignin-degrading basidiomycete Phanerochaete chrysosporium. Journal of Bacteriology 174(7):2131-2137, 1992. doi:10.1128/jb.174.7.2131-2137.1992.
- Kaewlaoyoong A, Cheng CY, Lin C, Chen JR, Huang WY, Sriprom P. White rot fungus Pleurotus pulmonarius enhanced bioremediation of highly PCDD/F-contaminated field soil via solid state fermentation. Science of the Total Environment 738:139670, 2020. doi:10.1016/j.scitotenv.2020.139670.
- Kaewlaoyoong A, Chen JR, Cheng CY, Lin C, Cheruiyot NK, Sriprom P. Innovative mycoremediation technique for treating unsterilized PCDD/F-contaminated field soil and the exploration of chlorinated metabolites. Environmental Pollution 289:117869, 2021. doi:10.1016/j.envpol.2021.117869.