We, as humankind, are in the midst of a ‘Great Plastic Age’ – and its effects will last across the ages (see the Plastics section for more information). The most prevalent issue with plastic production is the problem of disposal, with many plastics estimated to degrade over the course of centuries or millennia, if ever. Have you ever used and disposed of a polyester PET water bottle? Then you’ve already left your own personal legacy, as PET (Polyethylene terephthalate) does not naturally biodegrade.
Chances are, if you’ve already reached this website, you are aware of the devastating effect our plastic waste has on the ecosystem. If we could stop producing so much plastic, that would be a tremendous aid; however, we are past the point of no return, with plastic lifespans exceeding our lifespans by far.
Luckily, bacterium has been discovered in 2016 that has naturally evolved to eat plastic (read the fascinating original article here). Since that day, scientist have been scrambling to use this knowledge to create a viable and efficient disposal system for plastics.
The bacterium, Ideonella sakaiensis, was discovered near a Japanese bottle-recycling dump and has also been spotted in some other PET-polluted sites. It is not only capable of breaking the molecular bonds of PET (polyester), but thrives on it. For those of the chemical mind: the strain, when grown on polyester plastic, produces two different enzymes that can hydrolyze PET as well as its reaction intermediate, which efficiently converts PET into two monomers (terephthalic acid and ethylene glycol). To clarify, the bacterium can live on the low-quality plastic, secreting two natural catalysts that break down the PET to its environmentally safe components.
Since this discovery, researchers have examined the structure of the I. sakaiensis produced enzymes, trying to figure out how such a strain could have evolved in response to our plastic crisis. Yet instead of an understanding of history, they accidentally tweaked an enzyme in such a way that they improved it…by 20%. While this is impressive, it also indicates that this newly encountered bacteria is also not fully optimized. Perhaps in years to come, we can use bacteria and enzymes as an ecologically safe alternative to harsher industrial catalysts. In fact, patents have already been filed by the researchers at the University of Portsmouth as well as by the US National Renewable Energy Laboratory in Colorado.
This is quite the difference from another strain of bacteria found in 2015 – Fusarium oxysporum cutinase (FoCut5a) – a fungus enzyme that has also been found to ‘eat’ PET plastics. For one, it is already much more efficient. Additionally, bacteria are much easier to control in industrial environments than fungi. In a scientific field that is constantly battling the cheap methods of ‘fresh’ plastic, economic constraints are highly applicable.
Despite changing public opinion, at this moment in time true change will need the support of our resistant governments and businesses.
There may still be a long way to go before we are truly capable of harnessing the rapid power of enzymes, but studies are indicating more and more that it is possible. If we could change the I. sakaiensis bacteria to survive at extreme conditions (above 70 C), for example, then we could degrade PET in its viscous, rather than glassy state, and improve degradation times by 10-100%.
What is truly fascinating is the popular theory that many of these strains may have evolved in response to the current plastic crisis. Perhaps with an open mind and powerful scientific teams we can discover more of these gifts and aids nature is providing us with.