Labcoat Fridays: Fungus Eats (Some) Plastic

If you read this article about fungi discovered in the Amazon that can eat plastic, you might get the idea that the happy science accident happened yet again, and all our pollution problems will soon be resolved. Just like penicillin was accidentally discovered in a moldy Petri dish, you may form an image of clueless undergraduates poking around the Amazon rainforest, collecting random plant samples, and fortuitously stumbling upon an all-important discovery. Perhaps, when the samples make their way back to the lab, a student notices that the Ziploc bag in which one of the samples was transported seems to have developed some holes, as if it was eaten from the inside. Oh happy day! The undergrads discovered a fungus that eats plastic - an answer to our pollution problem!

From here. Originally adapted from here.

That's not exactly what happened. The truth behind this somewhat misleading article was uncovered in the originally published research paper. Research into biodegradability of polyurethane (the only plastic that this fungus has been able to digest so far) goes back to the middle of last century - the authors cite papers that date back to as early as the 1960s. The article says that until now, polyurethane (which is found in many everyday items, like garden hoses and shoes) would have stuck around forever as nothing could possibly decompose it. But that's not entirely true - scientists have been aware of polyurethane's susceptibility to biodegradation for over half a century now, and you can bet that the researchers embarking on the expedition to the Amazon were aware of this previous work. In fact, you don't have to bet - they say so themselves in the paper.

And no, the undergrads were not aimlessly poking around the rainforest, trying to learn the process of doing field work (although there was some of that, too). The exploration effort was specifically aimed at discovering new organisms that could degrade polymers. Various plant samples were collected with this goal in mind, and the samples were transported back to the lab in polyethylene bags (same material that grocery plastic bags are made of). So, no, the fungus did not make a hole in the bag. And it became obvious that the fungus does not eat ALL the plastic (it couldn't handle polyethylene). So the pollution problem still remains.

However, the research group did make some interesting findings. For example, the fungus that they isolated (and later demonstrated its ability to digest polyurethane) is an endophyte, which means that it lives in a plant without harming the plant itself. This was a first discovery of endyphytes that degrade plastic. In addition, this new fungus (or really, a family of fungi) degrades polyurethane at a much faster pace than the previously discovered organisms. This improvement was quite significant - the fungus was able to eat all the polyurethane it was fed within five days, while the previously identified organisms digested the plastic in fifteen days or longer. Even more importantly, the researchers demonstrated for the first time ever that a fungus can degrade polyurethane without needing oxygen. This is a big deal when it comes to battling the pollution problem: landfills are full of piles of trash, and except for the outer surface, most of the trash does not get exposed to air. So if plastic degradation required access to oxygen/air, then it would not be very effective in clearing the landfill. But a fungus that can do this without oxygen holds some real promise in beginning to solve the pollution problem.

Make no mistake, though - the day our plastic pollution problem disappears is far away. So far, only polyurethane has been found to be susceptible to fungus degradation. Many other plastics that are prevalent in our everyday lives are much more resistant, and so far no biological solution has been found to address that problem. Still, we have a lot to learn from nature - it keeps developing new ways to heal itself despite our best efforts to pollute the planet.