Laboratory Researchers Uncover Amazonian Fungus That Can ‘Eat’ Plastic
Plastic is a material that is difficult to decompose and takes an extremely long time to break down. Therefore, it is considered a non-degradable substance. The accumulation of plastic leads to solid waste on the Earth's surface, and if ingested, it can cause death in animals. Over time, plastic is exposed to UV rays, forming fine particles that increase its surface area and mobility.
As a result, these microplastics more easily enter the food chain, posing serious threats to all living beings. The disposal of plastic waste into the ocean leads to the accumulation of toxic chemicals, which can interfere with digestion, block digestive tracts, and impair reproduction in marine organisms. Plastic decomposition can be achieved through several methods, such as photodegradation, thermo-oxidative degradation, hydrolytic degradation, and biodegradation.
Biodegradation is considered a more environmentally friendly method because the breakdown process is carried out by microbes. In this method, fungi grow on the plastic surface and consume it as a food source. Fungi digest plastic by secreting degradative enzymes (such as cutinase, lipase, protease, esterase, etc.).
Degrading Fungi Found in the Amazon
One of the major discoveries made by a research team from Yale University during an expedition to the Amazon rainforest was the fungus Pestalotiopsis microspora, which is capable of degrading polyurethane (a type of plastic that is particularly difficult to break down). Pestalotiopsis can be found in oceans, rivers, lakes, the air, soil, and in various plant tissues. Depending on its habitat, Pestalotiopsis species display different ecological functions.
For example, this fungus can act as a saprophyte, living on plant tissue and causing disease in leaves, twigs, and flowers. It is classified as an endophytic fungus, meaning it lives within plant tissues without causing disease. This particular endophytic species, discovered in the Amazon rainforest, gained attention for its ability to degrade polyurethane.
Plastic Degradation Mechanism
Plastic degradation is facilitated by enzymes that can break chemical bonds in the polyurethane chain. The enzymes involved include cutinase, lipase, protease, esterase, and others. This enzymatic mechanism is carried out by fungi growing on the surface of the plastic.
Fungi like Pestalotiopsis microspora attach themselves to the plastic and secrete enzymes to consume it as a nutrient source. Over time, the polymers in plastic are depolymerized and degraded, ultimately producing water, carbon dioxide, and methane as end products. The fungus also produces hydrophobins—compounds that help coat its hyphae with hydrophobic substrates.
Intracellular enzymes in fungi play a role in detoxification and adaptation. This system is mediated by Phase I enzymes (epoxidases) and Phase II enzymes (transferases), which are involved in oxidation and conjugation reactions. Additionally, fungi produce extracellular enzymes (hydrolases) involved in the degradation of polysaccharides and lignin.
The enzymatic activity of fungi is influenced by environmental factors such as humidity, pH, temperature, and more. Fungi thrive in moist environments with a pH level that activates their plastic-degrading enzymes. Temperature also plays a role in biodegradation, as polymers with higher melting points take longer to degrade than those with lower melting points.
A unique feature of Pestalotiopsis microspora is its ability to degrade plastic even in anaerobic (oxygen-free) conditions, making it highly promising for use in closed environments such as landfills. Future research will focus on genetically modifying fungi to enhance their efficiency in breaking down various types of plastics. Biology-based technologies are becoming a promising alternative to address the global plastic waste problem. Utilizing plastic-degrading microbes supports ecosystem safety in plastic recycling systems.
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References:
Ekanayaka, A. H., Tibpromma, S., Dai, D., Xu, R., Suwannarach, N., Stephenson, S. L., Dao, C., & Karunarathna, S. C. (2022). A review of the fungi that degrade plastic. Journal of Fungi, 8(8), 772. https://doi.org/10.3390/jof8080772
Srikanth, M., Sandeep, T. S. R. S., Sucharitha, K., & Godi, S. (2022). Biodegradation of plastic polymers by fungi: A brief review. Bioresources and Bioprocessing, 9, 42. https://doi.org/10.1186/s40643-022-00532-4
Wu, C., Wang, Y., & Yang, Y. (2022). Pestalotiopsis diversity: Species, dispositions, secondary metabolites, and bioactivities. Molecules, 27(22), 8088. https://doi.org/10.3390/molecules27228088
