Plastic degrading enzymes in wax worm saliva
The world uses over 500 billion plastic bags a year. Currently there are no feasible ways to manage our plastic waste. But, a few years back, we covered a story here on the programme where Cambridge University scientists discovered that an insect species called a wax worm appeared to be able to eat plastic! Now they’ve worked out how the animals do it: enzymes in the worm’s saliva can oxidise the plastic polymer molecules, meaning it might be possible to mass produce them and come up with an environmentally friendly solution to plastic pollution, as Risa Bagwandin heard from Federica Bertocchini…
Federica - If we think about plastic waste accumulation and the potential solutions we have, we can say that to date there's not much around. There's a little bit of recycling, which is not properly working, it is not solving the problem. Plastic is otherwise burnt, with the environmental cost or ends up in landfill sites. So the problem is huge and plastic production is not decreasing anytime soon. So we working on insect, in particular the wax worm. We found a few years ago that this insect was capable of degrading plastic. We managed to find the enzymes capable of doing that, and these enzymes have been found in the saliva of the worm
Risa - How fast can wax worm saliva breakdown plastic?
Federica - We see that in a few hours there is oxidation. And if we extend the time with more enzymes, this increases and we talk about hours 5, 6, 7 hours.
Risa - So this takes place in a matter of hours. And how does this compare to if plastic had to decompose on its own?
Federica - Now in the environment, when we think of a plastic bag thrown out there. It takes a long time. And the bottleneck of degradation is oxidation, which is the first step. And this can be overcome by these enzymes.
Risa - What conditions do these enzymes work in? Do we need any prior treatment of the plastic?
Federica - No pretreatment, plastic as it is, room temperature, neutral pH. That is it.
Risa - So we don't need any harsh conditions for this reaction or the enzymes to work on plastic?
Federica - No, not at all.
Risa - Do we know why these worms have these enzymes?
Federica - This is a good question. No, we don't know. And this is actually the next priority in research. We would like to know why they have this capacity and how they work.
Risa - Now that we've identified these enzymes, can we make them in the laboratory?
Federica - Yes. In fact, the enzymes we have been working on in the paper. They are recombinant proteins, meaning that they've been made in a lab.
Risa - And what do you envision as the potential application of these enzymes in terms of waste management?
Federica - What I envision is a system in which plastic can be degraded in a controlled environment. You may imagine piles of plastic collected and a watery solution poured on top of that.