We, as humans, have a large and usually disruptive effect on our environment. The levels of carbon dioxide in the atmosphere are rising due to human activity resulting in an increase in average global temperatures. We also produce more than 275 million metric tons of plastic in a year, between 10 and 28 billion pounds of which ends up in the ocean, disrupting the ecosystems there. Just to give a few examples.
But the news isn’t always bad. Sometimes, scientists discover ways to counter balance our influence – even just by a little – either through a better understanding of creatures already found in nature or through genetic engineering. I’m talking about the recent, accidental, discovery of caterpillars that actually eat plastic waste and the ongoing work to genetically engineer bacteria to absorb carbon dioxide or CO2.
Caterpillars that can eat plastic waste
Caterpillars are known as agricultural pests, producers of silk, and, of course, future butterflies and moths. One species of caterpillar known as Galleria mellonella, the larvae stage for the greater wax moth, is a known parasite in beehives that feeds on beeswax. When biochemist and amateur beekeeper, Federica Bertocchini, removed the caterpillars from her honeycomb and tossed them into a plastic bag, she soon discovered that they had chewed right through the plastic in several spots within only a few hours.
Such wax worms have been reported as plastic eaters before but whether they actually metabolized the plastic into something else or simply chewed it down before excreting it in a similar yet micro-sized particle form was not known. For example, the moths that are known to eat your wool sweaters aren’t too picky. They will help themselves to clothes made of other materials as well, but any artificial fibers tend to just get excreted as smaller particles while only the wool is actually processed by the moth’s digestion.
Together with her collaborators Paola Bombelli and Chris Howe at the Department of Biochemistry at the University of Cambridge, Bertocchini decided to test the degradation of plastic by the wax worms in a more controlled environment. They found that the caterpillars made their way through a supermarket plastic bag in less than an hour and were able to consume 92 milligrams of plastic in 12 hours. The same amount of plastic could require as long as hundreds of years to decompose, but the caterpillars gobbled it up in less than a day.
Even more importantly for potential solutions to our plastic overproduction problem, the scientists determined that the larvae were actually biodegrading the polyethylene and converting it into ethylene glycol. The authors note in their study that, together with polypropylene, polyethylene represents 92% of the world’s total plastic production and makes up ~40% of plastic packaging.
Rather than mass production of wax worms – think of the bees! – the next step toward utilizing their ability to potentially reduce plastic waste is to determine what exactly causes the polyethylene to degrade. The authors of the study suspect either an enzyme produced by the worm or by bacteria in the worm’s gut is the cause. One piece of evidence for an enzyme: they found that a mashed up pile of worms still ate through the plastic.
Bacteria that can absorb carbon dioxide
While some scientists are looking to caterpillars to solve our plastic problem, others are investigating the possibility that bacteria might be able to help counter balance the excess CO2 that we produce. For example, researchers at the Department of Energy’s National Renewable Energy Lab, have found the bacterium Clostridium thermocellum, already known for its ability to break down cellulose into usable biofuels, can – surprisingly - metabolize carbon dioxide as well. The authors note that there is still a long way to go in understanding the mechanism at work to take up the CO2 before we can hope to set our sights on reducing atmospheric levels of the greenhouse gas.
Scientists, of course, can’t always wait for serendipitous discoveries to cross their lab bench, or their apiary as the case may be. Professor Daniel Nocera of Harvard, for example, announced last year that he had successfully engineered a bacteria to absorb carbon dioxide and hydrogen and convert them into fuel in the form of alcohol. Nocera is careful to point out that the bacteria, known as Ralston eutropha, are not likely to be able to solve the problem of excess CO2 in the atmosphere. However, the production of alcohol fuels like isopropanol, and isobutanol, could help by alleviating pressure on fossil fuels.
While nature – and science! – may provide alternative solutions to our environmental problems, these caterpillars and bacteria can only do so much. We are not off the hook and should continue to reduce our carbon footprint when we can.
Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.
Wax worm image courtesy of shutterstock.
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