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Can bacteria help us recycle plastic waste?

In March 2016, the world woke up to the sensational news of the discovery of bacteria with the ability to decompose or ‘eat’ plastic. The discovery happened when scientists scooped up some sludge from outside a bottle recycling facility in Osaka, Japan. But, the newly discovered bacteria, Ideonella sakaiensis, was able to decompose only the plastic varieties called PET, from which water bottles and containers are commonly made, and the process of decomposition was rather tedious. It was duly concluded that the bacterial action was not fast enough to mitigate the millions of tonnes of plastic waste generated annually. Since then, researchers started exploring the possibility of building industrial-scale amenities where micro-organisms can munch on piles of plastic. However, environmental experts have cautioned that commercial use of plastic-eating microbes is years away and the potential threat they cause if released into the atmosphere should not get overlooked.

To make the commercialization of plastic-eating microbes a reality, scientists need to focus on the evolution of bacteria. Microbes took millions of years to learn how to biodegrade organic matter such as tree leaves and fruits, it might take quite a long time for them to learn to degrade plastics, as plastics have only been around since the 1950s. For instance, seaweed has been around ever since the beginning of evolution, there is a variety of microbes and organisms that can break it down. But, as a sliver of hope, a year after the discovery of Ideonella sakaiensis in Osaka, scientists have reported fungi and bacteria capable of degrading polyurethane plastic. This is a sign that the evolution of plastic-eating microbes has already begun. To extract maximum use out of these bacteria, they must be carefully bioengineered to expedite the decomposing action. Scientists in the UK and U.S. have managed to modify bacteria by combining two different enzymes in plastic-eating bacteria into one ‘super enzyme’. With bioengineering firms coming forward to experiment with the findings, improvements in the technology are being expected to advance in the coming years.

Commercialization of such bacteria may become a reality in the coming months when Caribos, a French firm, will establish a demonstration plant capable of enzymatically degrading plastic. This plant intends to convert PET plastic back into a feedstock for the creation of more plastics. If this results in successful operation, PepsiCo and Nestle will partner with Caribos to achieve long-standing goals of recycling their plastic bottles back into the production line. Recycling plastic bottles was unsuccessful earlier as no methods ensured complete fragmentation of the plastic bottles.

As the hopes of steady riddance from plastic are high, experts have cautioned that they would still face major limitations and be dangerous. For starters, the bacteria in the spotlight of experiments so far digest only PET. Other materials, such as HDPE, which is primarily used to make harder materials such as shampoo bottles or pipes, are more difficult to degrade and so far have not been effectively degraded by any of the said microbes. Another major disadvantage is the chemical nature of the decomposition. The bacteria are unable to decompose plastic to core elemental building blocks including hydrogen and carbon. Instead, they break up polymers into monomers, which can be later recycled into plastics. This is the principle used for the Caribos plant as well. Another potential threat is the release of genetically modified microorganisms into nature. Without a detailed study of how these microbes affect flora and fauna, their release might yield catastrophic results.

Since the disadvantages outweigh the advantages in the case of plastic digesting microbes, the best way to tackle the plastic crisis at the moment is by switching to reusable alternatives and ensuring that non-biodegradable items end up in landfills and not out openly in the environment. Plastics can be substituted with cleaner alternatives such as metal, wood, glass, aluminum, and steel that can be recycled indefinitely. By buying eco-friendly products, we can help alleviate the problem of ever-increasing solid waste.

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