Plastic- as you all know is the most revolutionary yet non-biodegradable invention. The first fully synthesized plastic, Bakelite was invented by Leo Baekland in 1907. What started as a revolution has now become pollution. It is hailed as strong due to its durability and versatility. However, thanks to its recalcitrant nature, it has started to affect humans and marine life alike. This makes it stand atop the list of problems to be solved by environmentalists. Ever since scientists and environmentalists alike have been looking for ways to get rid of these plastics. While they do their part, nature has shown us a potential solution in the form of plastic-eating bacteria and fungi.
Plastic-eating Bacteria
Some bacteria like Ideonella sakaiensis and Bacillus subtitlis can break down a group of plastics called Polyethylene terephthalate (PET). Specific enzymes like PETase and METHase help them break down the plastics.
Plastic-eating fungi
While plastic-eating bacteria sounds promising, yet another group of organisms- Fungi, specifically mushrooms have been found to be more promising. Certain mushrooms can not just thrive, but devour plastics. Specific enzymes present in certain fungi can help break down certain types of plastics into simpler compounds. Some of these compounds can potentially act as an energy source for the fungi.
Fungi can be an ideal choice due to their diversity and adaptability. Here are some promising fungi-
- Pestalotiopsis microspora can thrive in both aerobic and anaerobic conditions making it an ideal candidate for tackling plastic pollution, especially in landfills.
- Engyodontium album and Aspergillus terreus can break a specific type of plastic-polypropylene
- Parangiodontium albums, from the seas, can degrade polyethylene when exposed to UV light.
Plastic-eating mushrooms
A group of mushrooms could digest popular plastic materials like polyurethane and polyethylene. Daily use items like clothes, appliances, and insulating foam contain polyurethane. Polyethylene can be seen in plastic food packaging.
How does a fungi utilize plastic waste?
While not all fungi may munch on plastic like it is a snack, some do. Others have found different ways to utilize the plastic. Here are a few instances-
- Some microbes can latch onto plastics as they tend to last longer than other natural materials and repel water.
- Some fungi species can gobble up petroleum-sourced polymers.
- Some mushrooms can break down complex chains of plastic polyethylene and polyvinyl chloride into monomers and utilize them. They probably learned to ‘eat’ plastics by breaking down long chains of complex polymers into simpler compounds from plants and organic material.
- Pleurotus australis, commonly called the oyster mushroom can degrade the super-durable, tough-to-degrade Poly Ethelyne Tetrapthalate (PET).
- Most products are made of a mix of plastics rather than a single type. One organism that could break down a mix of plastic is P.ostreatus.
How it works?
The fungi use their mycelia to attach to the film of plastic and secrete specific enzymes that convert plastic polymers into small molecules. The film eventually collapses, developing cracks, pits, and cavities. Finally, its surface erodes and becomes rough.
A pioneer in plastic degradation- Pestalotiopsis microspora
This tiny fungus started the plastic degradation revolution. Discovered in 2011, this fungus belonging to the genus Pestalotiopsis could break down polyurethane to organic matter within the lab environment. The best part.. 2 species of this genus could survive without oxygen, perfect for landfills where you can find ample plastics to degrade. They could also degrade plastics suspended in liquids making it a perfect choice for plastics in the oceans. What’s more promising is that a specific species in this genus- the Pestalotiopsis microspora could degrade polyurethane in 2 weeks.
Could their power be harnessed to curb plastic pollution?
The enzymes used by these fungi can be harnessed and manufactured on a large scale to tackle plastic pollution. However, they do have certain cons.
Limitations
- They break down the plastic very slowly. It can take up to several days or even months to degrade plastics. With the current pace of plastic pollution, it is impossible to break down plastics at this rate.
- They cannot work on all types of plastics. This means plastics in your household items like CDs and electronics cannot be degraded.
- They could have worked out in several laboratory conditions. But, do they work at an industrial scale or a polluted site? We still need to research that.
Despite the limitations, two Dutch scientists teamed up with an Australian designer Katharina Unger to develop a ‘Fungi mutarium’, a prototype to grow edible fungal biomass! They used agar gelatine pods that nourish the fungus with sugars and starch until we stuffed UV-treated plastic in the middle. In a few months, the fungus can fully digest the plastic leaving a puffy mushroom-like liquorice-smelling edible mushroom! Could this be foreseen in households to recycle their plastic wastes? Comment your thoughts.
Other interesting organisms that can eat plastic-
- Wax worms- Wax worms are the larvae (caterpillars) of wax moths, mainly the greater wax moths. They gained the spotlight in 2017 when they were seen chewing on a plastic bag. This inspired scientists to harness its power for plastic degradation.
- Superworm Zophobas morio- These chunky, wriggly larvae are commonly used as feeder insects and are also gaining attention in plastic biodegradation research. It has developed a liking for polystyrene, a commonly used plastic. Interestingly, their gut bacteria is responsible for this key process.
From pollution to Solution- one spore at a time!
While fungi may not be the silver bullet to eliminate all plastic waste overnight, they offer a glimpse into how nature may help fix human problems. With continued research, innovation, and perhaps a bit of bioengineering, today’s humble mushroom could become tomorrow’s warrior. Check out a related video on itsbiodiaries.