Plastic-eating Microbes

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The mass production of plastic has skyrocketed from around two million tonnes annually to a staggering 380 million in the last seven decades or so, and around eight million tonnes wash into the ocean each year. This is having catastrophic effects on the animals that call the ocean home and the people who rely on oceanic ecosystems to sustain their livelihood. The inability of ocean animals like sea turtles, seabirds and seals to distinguish between what is food and what is trash, as such distinction is not natural, means that the abundance of plastic waste in the sea acts as a minefield of choking hazards for its abundance of marine life. It is estimated that by 2050, 99% of all species of seabirds will be eating plastic and 95% of all individual seabirds will fall victim to the harmful effects of consuming plastic. The predicted percentage of species that will consume plastic is 65%, which is a jump from the historical average of 26%. This is one of the most pressing problems in modern history, and whilst many start-up’s and NGO’s are breaking their backs by cleaning up local areas, not much change is happening. It seems that to cover all the word’s oceans and seas we need a different approach, something stronger in our arsenal, potentially like a plastic-eating microbe.

In Japan in 2016 scientists discovered a bacterium that was feeding on plastic packaging material as an energy source, with help from a pair of purposely evolved enzymes. Since this initial discovery, some interesting advances have been made: In 2018, a group of scientists in the US built on this research to produce an engineered enzyme that could consume plastics with around 20 percent greater efficiency. That same team then developed an even more advanced version in 2020, which they described as a super enzyme that could digest plastic waste at six times the speed.

What’s even more interesting is the results from new research by Sweden’s Chalmers University of Technology, which analysed samples of environmental DNA which was sourced from hundreds of ocean and terrestrial locations around the world, revealing a total of 30,000 enzymes spread across the ocean with the potential to degrade 10 types of common plastics. Study author Aleksej Zelezniak stated that they “found multiple lines of evidence supporting the fact that the global microbiome’s plastic-degrading potential correlates strongly with measurements of environmental plastic pollution – a significant demonstration of how the environment is responding to the pressures we are placing on it,” meaning that these plastic-eating microbes are better at their job the more concentrated in plastic the area is.

However, we should be careful of the potential downsides of this microbial solution to waste in the oceans. Firstly, there are plenty of plastics in the ocean which we do not want to discard of, such as plastic water pipes, sewer pipes, cable insulation, foundation materials, drainage pipe, and much more. If no distinction can be made from the plastic we want to be eaten and that which is used as material in construction then problems could be caused. Furthermore,  it’s unclear yet whether this enzyme is safe to use in widespread environmental remediation, as enzyme spraying into the sea has a history of unintended consequences and side effects.  For example, previous experiments showed that floating plastics deliver disease-causing microbes to corals, and therefore ecosystems may be at risk if this consequence is not considered, an especially worrying consequence as coral reefs are becoming increasingly endangered.

As it stands there is still is little known about these microbes. However, “The next step would be to test the most promising enzyme candidates in the lab to closely investigate their properties and the rate of plastic degradation they can achieve,” says Zelezniak. “From there you could engineer microbial communities with targeted degrading functions for specific polymer types.” Therefore, this currently sub-par solution may become a viable way to clean the oceans, yet this may take time.

For the time being, most environmentalists believe that the first order of action is to tackle this problem at its source by reducing our reliance of single-use plastics. Once this is regulated to a more environmentally optimum level, the microbes can be used to whittle away the remaining plastic waste in the sea and mediate the levels from there after.

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