Part I: How Mycoremediation Can Change The Polluted World As We Know It
There are many things of unfathomable importance that most of us never think about. They exist in cryptic realms beyond the sight of the naked eye yet play an unparalleled role in our lives. The fungal kingdom and its great diversity of species are one of these important things.
You see, fungi are the unsung heroes of the natural world. They are the great mediators and connectors of life, continuously working behind the scenes to shape life as we know it. While it's plants and their photosynthetic abilities that often get the spotlight above ground, it's the fungi that make this all possible below ground.
After all, it's only by allying with fungi that plants have been able to flourish and shape today's terrestrial ecosystems. About 95% of plants form symbiotic relationships with fungi in their roots, an ancestral collaboration that dates back to the arrival of plants on land. It's likely that without this symbiotic relationship, plants wouldn't have been keen to make this metamorphic leap from water to land, at least not as quickly as they did.
As we'll discuss in more detail later in the story, this is just the tip of the iceberg of fungi's role in the environment. Fungi are important players in earth's natural cycles, influencing the flow of important soil nutrients and carbon. They're also major pathogens, greatly influencing and regulating population dynamics in ecosystems. Last but not least, fungi form an important part of the microbiome for both plants and animals.
Beyond this, fungi also play a role in everyday human life. They have helped us develop life-saving medicines like penicillin; they're used for the fermentation of culinary delicacies (Bread, wine, and cheese, anyone?), and today there are other novel uses being developed. For example, fungi are now used for the production of sustainable materials that can replace styrofoam and leather.
One of the most recent applications of fungi is in the remediation of environmental pollution. This is an area of study known as mycoremediation. Mycoremediation harnesses the power of fungi to break down, transform, or sequester environmental contaminants in ways that remove them from the environment. This includes the remediation of a grand diversity of pollutants ranging from crude oil to pharmaceutical waste and potentially even plastic.
It's hard to imagine how you even begin to harness fungi in this way, especially for those illiterate about the intricacies of fungal ecology. It's something this story will be discussing in detail after we cover some basics about fungi, who they are, and the roles they play in nature and human society.
When most people think of fungi, they imagine a store-bought button mushroom. A mushroom like that which you find on a pizza or in the infamous can of mushroom soup. A rather large percentage of people say they don't like mushrooms, although most people have only tried one variety out of the more than 600 edible species consumed around the world.
For others, fungi may have an even less appealing association; athlete's foot or other fungal infections. Others think of molds, rotting foods, and a wide variety of unpleasant things. To say the least, fungi are often given a bad wrap.
Yet, considering you've stuck with me this far, you probably realize fungi aren't all bad. As a matter of fact, they've been getting quite a lot of positive attention in the media and environmentally conscious circles over the past couple of years. There's a good reason for it; fungi hold solutions to many of our modern-day problems.
Fungi are a kingdom of life with incredible diversity. Compared to the other kingdoms, they are often considered a "mega-kingdom" because the estimated 5.1 million species within the kingdom are so diverse. From single-celled yeasts to networks of filamentous mycelium acres in size (arguably the largest organism on the planet), their presence is ubiquitous wherever life is present.
Yeasts, for example, are almost everywhere in nature. They grow on the surface of leaves, fruits, and even on our own skin. Yeasts even exist in the air we breathe! Traditional lambic beer brewers from Belgium were very well aware of this and would place large vats of wort to cool outside in order to capture these airborne yeasts.
Mycelium is the multicellular and filamentous form of fungi. You've probably seen cobweb-like mycelium in the forest beneath the leaf litter or decomposing wood. Mycelium is composed of thousands of thin hyphal threads that are one cell in width and 100 times thinner than a human hair.
It is from mycelium that the mushrooms we are familiar with are produced. In fact, mushrooms are only the reproductive structure, akin to a flower, while mycelium is the actual body of the fungus. Mushrooms produce dust-like spores, sometimes trillions of them (as is the case with the Giant Puffball Mushroom), in hopes that a few will land in suitable conditions to germinate and grow.
Most mushroom-forming fungi are classified as decomposers in nature. They acquire all their nourishment by decomposing organic substrates like wood, manure, leaves, and almost anything you can think of. Fungi are particularly effective decomposers for a variety of reasons, but the most relevant is that they produce unique peroxidase enzymes. These are capable of breaking down many different complex organic compounds that nothing else in nature can.
For example, the structural compound called Lignin that makes plants tough and woody is almost exclusively broken down by these fungal enzymes. Without these enzymes, forests would accumulate kilometers of undecomposed debris on the forest floor. This would not only have major consequences on our planet's carbon cycle, but it would mean that nutrients locked up within these plant materials would not be released back into the soils where they came from.
Other than decomposers, fungi can also be classified ecologically as "mycorrhizal fungi." These are the symbiotic fungi we discussed earlier, which associate with the roots of plants. Their name comes from the word mycorrhizae which translates to "fungus root" in greek. This name is actually a rather good description of the functionality of these fungi.
They are equipped by plants to extend and improve the capacity of their roots beyond what they are capable of on their own. Since fungal hyphae can be thousands of times thinner than tree roots, they are capable of squeezing between soil particles and greatly improving the surface area of nutrient and water absorption. Some mycorrhizal fungi also retain attributes of decomposers, giving plant roots exclusive access to nutrients locked up within undecomposed organic materials.
Furthermore, mycorrhizal fungi also attribute more than an all-inclusive pass to the soil nutrients and water. They also protect plants against threats like pests and disease and form an underground network known as the "Wood Wide Web" that helps plants communicate with each other.
The wood wide web is used by trees to warn each other of incoming threats and even to circulate nutrients and carbon from one tree to another. The "Mother Tree" concept shows that older mature trees will allocate carbon to their offspring via the wood wide web to give them a head start in the dark and competitive understory of a forest.
What's curious about mycorrhizal fungi is that they do not obtain their energy by decomposing organic debris like decomposer fungi. Instead, they receive it as glucose directly from their plant hosts. In some cases, plants will allocate up to 1/5 of all their photosynthetically derived carbon to their fungal partners. This means for every 5kg of carbon sequestered through photosynthesis, up to 1kg can enter the soil directly through the mycorrhizal network.
This is important because it means mycorrhizal fungi end up being a major carbon sink, storing carbon in soils and preventing it from entering our atmosphere, where it acts as a greenhouse gas. A study conducted by scientists at the Swedish University of Agricultural Sciences showed that 50-70% of soil carbon in their local forests originated from tree roots and their associated mycorrhizal fungi.
Considering that forests store 7.6 billion metric tonnes of CO2 per year (or 1.5 times more carbon than the United States emits annually), these mycorrhizal fungi are huge players in our global carbon cycle and the ongoing fight to tackle global climate change.
While the main topic of this story is about how fungi can help "heal" the environment, it is worth noting that fungi also play an important role in human health.
Mushrooms, as you may know, are nutritious foods, but they also have a long list of health benefits. This includes helping with many of the chronic diseases caused by our modern-day lifestyles and diet. Moreover, some varieties are specifically considered "medicinal mushrooms" and have been consumed traditionally for centuries for the treatment of specific ailments.
One of the main reasons mushrooms are so beneficial to human health is because of polysaccharides present within the cellular framework of all mushrooms. These are called beta-glucans, and they are ubiquitously present within the scaffolding of fungal cell walls. While some plants also produce beta-glucans, it is only fungal beta-glucans that have such powerful effects.
For example, beta-glucans from a medicinal mushroom known as Turkey Tail have been shown to have anti-cancer properties that can increase the effectiveness of conventional cancer therapies. In China, Japan, and other eastern countries, Turkey Tail beta-glucans are approved by the leading health agencies and readily prescribed as an adjunct therapy for cancer with costs covered by insurance providers. This is thanks to extensive research with dozens of human clinical trials with thousands of participants that confirm the effectiveness.
While Turkey Tail has been the most extensively studied, many different fungal beta-glucans have been shown to have anti-cancer properties. This includes edible mushrooms like Shiitake, Oyster, Maitake, and Lion's Mane or strictly medicinal species like Reishi, Artist Conk, and Chaga. Even beta-glucans from common yeasts are shown to have some health benefits.
The medicinal benefits of beta-glucans are largely tied to their effects on the immune system. They are considered immunoregulators because they help with the regulation of immune function, stimulating the production of immune cells when they are most needed. In the case of cancer patients, they help boost the levels of t-cells and other antibodies that directly target cancer cells. In some cases, they also make cancer cells chemosensitive, further improving the effectiveness of conventional treatments.
Yet, it's not just in the treatment of cancer that mushrooms are beneficial. They can help regulate cholesterol and blood sugar or even potentially help with nerve damage and memory loss. Medicinal mushrooms can be consumed in tea, capsules, extracts, and tinctures and are now even included in processed foods. Alternatively, just incorporating mushrooms (especially the gourmet varieties mentioned previously) into your diet can be a great way to get health benefits.
Let's now take a deep dive into mycoremediation and how fungi can help clean our environment Remember the peroxidase enzymes we discussed earlier in the story? These are the enzymes almost exclusively produced by fungi that break down complex woody compounds in plants. These are not only what prevent the kilometers of woody debris from accumulating in forests, but they also may hold the key to cleaning up man-made pollutants.
That's because these enzymes are particularly powerful and capable of breaking down complex carbon compounds, such as many different types of carbon-based pollutants. When fungi come in contact with these types of pollutants, they begin emitting these enzymes and essentially start using them as a food source. Once broken down, these compounds are less harmful and will be incorporated directly into fungal tissue or continue to be broken down into their simpler chemical components. In the end, what's left is just simple compounds no different than what is already persistent in natural ecosystems.
One of the most well-known cases of mycoremediation was carried out by the bearded and whimsical Paul Stamets, who has rapidly become one of the most well-known mycologists since the release of his book Mycelium Running in 2005. In his 2011 TED talk "6 Ways Mushrooms Can Save The World", Paul recounts his experiment cleaning crude oil from contaminated soil in Bellingham, Washington, USA.
"There were four piles saturated with diesel and other petroleum waste: one was a control pile; one pile was treated with enzymes; one pile was treated with bacteria, and our pile we inoculated with mushroom mycelium.
The mycelium absorbs the oil. The mycelium produces enzymes — peroxidases — that break carbon-hydrogen bonds. These are the same bonds that hold hydrocarbons together. So, the mycelium became saturated with the oil, and then, when we returned six weeks later, all the tarps were removed, and all the other piles were dead, dark, and stinky. We came back to our pile, it was covered with hundreds of pounds of oyster mushrooms, and the color changed to a light form. The enzymes remanufactured the hydrocarbons into carbohydrates — fungal sugars.
Some of these mushrooms are very happy mushrooms. They're very large. They're showing how much nutrition they could've obtained. But something else happened, which was an epiphany in my life. They sporulated, the spores attracted insects, the insects laid eggs, and eggs became larvae. Birds then came, bringing in seeds, and our pile became an oasis of life.
Whereas the other three piles were dead, dark, and stinky, and the PAH's — the aromatic hydrocarbons — went from 10,000 parts per million to less than 200 in eight weeks. The last image we don't have. The entire pile was a green berm of life. These are gateway species, vanguard species that open the door for other biological communities," summarized Semets.
While this is the most well-known case study on this topic, Stamets and his team are certainly not the only ones utilizing fungi to clean up oil. The Mycorenewal Project is working in one of the last wild places on our planet, the Amazon rainforest, to clean up crude oil using fungi in a similar approach to Stamets. Canadian researchers are also looking into fungi to clean up contamination from oil extraction in Alberta. In India, researchers are investigating mycoremediation for cleaning beach sand with contaminated crude oil. All around the world, scientists are collecting and testing novel fungal strains alongside ingenious methods to clean oil with fungi.
The same organization we mentioned earlier, which is working in the Amazon to clean up oil, has also applied mycoremediation in California to reduce toxic runoff from homes burned in wildfires. While it is only being pilot tested now, they are hoping their technique can help prevent toxic compounds like heavy metals and asbestos present in the ashes from entering sensitive waterways.
Their studies are conducted by placing straw wattles inoculated with oyster mushroom mycelium on contour berms around burned homes. The goal is that these inoculated waddles will intercept and filter contaminated waters. This is a form of mycoremediation known as microfiltration. Microfiltration has also been studied by the Battelle Laboratories in Washington to treat polluted wastewater from a dairy lagoon. They showed that by filtering water through basins filled with fungal mycelium and native plants, they were able to remove nutrients and up to 97% of fecal coliform bacteria in dairy lagoon runoff.
Scientists aren't only researching fungi for their abilities to break down oil but also countless other environmental pollutants. A scientific review released by researchers at the Lovely Professional University in India showed that mycoremediation has the potential for its use in the treatment of more than a dozen environmental pollutants. This includes herbicides, insecticides, pharmaceuticals, detergents, fertilizers, and other agricultural waste products.
Lastly, one of the most shared stories about mycoremediation is about a group of students who discovered a fungus in the Amazon rainforest with the ability to break down plastic. This fungus was a type of endophyte, meaning it is adapted to live inside plant tissues. After being collected, it was cultured in a laboratory and shown to be particularly effective at breaking down plastic. Endophytic fungi such as this one are the new frontier when it comes to the search for novel fungi.
Since then, researchers in China and Pakistan have also found other novel fungi with the potential to break down the polyurethane from which plastic is made. While it will be a while until fungi will help eat us out of the widespread environmental pollution caused by plastic, researchers think that there is great potential in the field of mycoremediation to someday properly treat plastic waste with fungi or fungal enzymes.
While mycoremediation is not widely applied in the clean-up of environmental pollution yet, it is a young science with an ever-expanding body of research. The scientific databases show that between 1990 to 2005, only about 100 scientific papers even mention the words mycoremediation. This is compared to more than 550 papers in 2020 alone and then more than 750 papers since the beginning of 2022.
Researchers today agree that mycoremediation is a completely feasible way to clean pollution but just exactly how to apply it cost-effectively is still being uncovered.
Fungi are powerful. They have so much to offer humanity at a time when we need them most. While they've been largely forgotten by our modern-day society, it may finally be their time to shine. So next time you see a mushroom fruiting on a lawn or perhaps growing from a log in the forest, take some time to admire it. Someday that mushroom may help make the world a better place.
They also have the potential to clean up pollution that is wreaking havoc on our environment. They can eat crude oil, pesticides, and even clean contaminated waters. Fungi have even been shown to help break down plastic. Whether you like mushrooms or not, consider giving fungi a second thought. They are a kingdom unlike you could imagine, with potential that should not be ignored.
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