Polyethylene terephthalate or PET can be found virtually everywhere – drinking bottles, food containers, synthetic clothes, carpets, and solar panels to name a few. It’s easy to produce and durable. Unfortunately, PET is a double-edged sword.
Ideonella Sakaiensis also known as plastic-eating bacteria
The qualities that make it so useful are the same ones that make it an environmental juggernaut. This incredibly tough material can last for decades, ending up in forests, beaches, rivers, oceans, and waterways.
Fortunately, researchers have found a glimmer of hope in our tiny allies. In March 2016, scientists from Osaka, Japan discovered bacteria that developed the ability to decompose plastic after taking water samples from sludge near a bottle recycling facility. Known as Ideonella sakaiensis, the bacteria can “eat” PET albeit at a very slow rate.
In 2017, biologists from Reed College in Portland have discovered colonies of bacteria capable of breaking down PET. For her thesis, Morgan Vague studied the relationship between bacteria and plastic. She collected soil samples around Galveston Bay in Texas to find out whether bacteria there have evolved to consume hydrocarbons. To her surprise, she found cultured bacteria from the site surviving on shards of water bottles.
Taking the study further, Prof. Jay Mellies and his students have discovered that the colonies are made up of five different types of bacteria that work together to consume PET and convert it into an energy source. “The novelty of our work is that we are using a group of bacteria to biodegrade PET plastic, whereas most efforts to date have focused on individual, isolated enzymes for this purpose,” he said.
In a similar study, German scientists discovered a group of bacteria capable of breaking down polyurethane plastic from a waste site in Leipzig.
For these bacteria to be useful, bioengineers need to make them do their tasks hundreds of times faster. Although there have been recent advancements, there is still a long way to go. In 2018, scientists in the U.K. successfully modified bacteria so they could start digesting plastic in just a few days. In 2020, the process was refined by combining two different enzymes from the bacteria into a more potent one.
Scientists hope that these discoveries can lead them to build large-scale facilities where enzymes feast on mounds of unwanted plastic or formulate spray-on liquids that can consume plastics in rivers or oceans.
With Covid-19 highlighting our dependence on plastics such as masks and food packaging, these advances are a ray of hope in our quest to finally end the world’s plastic waste problem. If current numbers hold, total plastic waste in the ocean will end up weighing as much as the entire fish population by 2050.
Unfortunately, we are still years away from the large-scale commercial use of plastic-eating microbes and even with these technologies in place, experts are wary that they will be severely limited and could potentially create more harm than good.
So far, studies have shown that the bacteria are only capable of breaking down PET, which is one of the seven major commercial types of plastic. Other plastics, such as HDPE, the prime ingredient in harder materials such as milk jugs and pipes, could be a harder case to crack. Moreover, bacteria can only degrade plastics into monomers and not into their core elemental ingredients which include carbon and hydrogen.
Spraying bacteria directly onto a plastic landfill isn’t an elegant solution, to say the least. Scientists warn that degrading polymers can release harmful chemicals stored up inside intact plastic. Others have also raised concerns over releasing genetically modified microorganisms into the environment.
Right now, the best way to handle the plastic waste crisis is by banning single-use plastic, switching to reusable alternatives, proper plastic disposal or recycling, and using biodegradable materials where possible.