Without getting too science-y, the enzyme the scientists tweaked had originally evolved to break down something known as polyethylene terephthalate, or PET, which is the plastic that's typically used in drinking bottles. Then, while studying it to see how that evolution in the garbage dump might have happened, they ended up making the enzyme even more powerful and better at breaking it down. In fact, the research suggests this newfangled version of the enzyme can get to work "eating" the plastic in just a few days, compared to the literally hundreds of years it would take nature to do the same thing. Even more promising, the scientists believe they can tweak the enzyme to make it even stronger, and speed up that process further.
Of course, it'll take time to implement this mutant enzyme in an effective way if and when it's vetted as a good solution, but there's plenty of work for it to get done. Only 14% of the roughly one million plastic bottles sold each minute around the globe actually gets recycled, per a report in The Guardian, and that means a hell of a lot of it is smothering the environment. Plastic bottles have also played a huge part in creating some alarmingly massive garbage patches in the oceans.