Scientists have discovered a marine fungus that can eat plastic

15.06.2024/00/30 XNUMX:XNUMX    7

The researchers discovered that the mushroom Parengyodontium album breaks down polyethylene in the ocean under the influence of UV rays, suggesting that similar fungi may also break down plastic in deeper waters.

Researchers, including those from NIOZ, have discovered that marine fungi can break down the plastic polyethylene after it is exposed to ultraviolet radiation from sunlight. Their findings, published in the journal Science of the Total Environment, show that numerous other fungi capable of degrading plastic probably live in deeper regions of the ocean.

Mushroom Parengyodontium album lives with other marine microbes in thin layers on plastic debris in the ocean. Marine microbiologists from the Royal Netherlands Institute for Marine Research (NIOZ) have discovered that a fungus is able to break down particles of the plastic polyethylene (PE), the most common type of plastic found in the ocean. NIOZ researchers collaborated with colleagues from Utrecht University, the Ocean Cleanup Foundation and research institutes in Paris, Copenhagen and St. Gallen, Switzerland. The discovery allows the fungus to join a very short list of marine fungi that break down plastic: only four species have been found to date. It is already known that a large number of bacteria are able to decompose plastic.

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Carefully monitor the degradation process

Researchers set out to find plastic-degrading microbes in plastic pollution hotspots in the North Pacific. From the collected plastic waste, they isolated a marine fungus, growing it in the laboratory on a special plastic that contains labeled carbon. Waksmaa: “These so-called 13C isotopes remain traceable in the food chain. It's like a tag that allows us to track where the carbon goes. We can then track it in the decay products."

Waksmaa is excited about the new discovery: "What makes this study scientifically outstanding is that we can quantify the degradation process." In the laboratory, Waksmaa and her team observed that the destruction of PE at P. album occurring at a rate of about 0,05 percent per day. "Our measurements also showed that the fungus does not use much of the carbon coming from the polyethylene when it is broken down. Most of the PE that uses P. album, turns into carbon dioxide, which the fungus releases again." Despite the fact that CO2 is a greenhouse gas, this process is not something that could create a new problem: the amount released by mushrooms is the same as the small amount released by humans when breathing.

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Only under the influence of UV

The researchers found that the presence of sunlight is necessary for the fungus to use PE as an energy source. Vaksmaa: "In the laboratory P. album only degrades PE that has been exposed to UV light for at least a short period of time. This means that in the ocean, the fungus can only break down plastic that originally floated near the surface," explains Waksmaa. "Ultraviolet light was already known to break down plastic mechanically, but our results show that it also promotes the biological degradation of plastic by marine fungi."

There are other mushrooms

Because many different plastics sink into deeper layers before being exposed to sunlight, P.album will not be able to break them all. Waksmaa expects that there are other, as yet unknown, fungi in the deeper parts of the ocean that also break down plastic. "Marine fungi can break down complex carbon materials. There are a large number of marine fungi, so it is likely that in addition to the four currently identified species, other species also contribute to the decomposition of plastic. There are still many questions about the dynamics of how plastic decomposes in deeper layers," says Waksmaa.

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Plastic soup

The search for organisms that break down plastic is urgent. Humans produce more than 400 billion kilograms of plastic each year, and this is expected to at least triple by 2060. Most of the plastic waste ends up in the sea: from the poles to the tropics, it floats on the surface. water, reaches a greater depth in the sea and eventually falls to the seabed.

Lead author Annika Waksmaa of NIOZ: “Large amounts of plastic end up in subtropical gyres, ring-shaped currents in the oceans where the seawater is almost stationary. This means that once the plastic has been moved there, it gets trapped. About 80 million kilograms of floating plastic has already accumulated in the North Pacific Subtropical Gyre in the Pacific Ocean alone, which is only one of six major gyres worldwide."