Waste processing

Wax worms could teach us how to bio-degrade plastic

Dr. Federica Bertocchini’s Plastic Entropy project, originated from the extraordinary discovery she made while cleaning her bee yards, kicked off in Madrid

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Instituto de Biomedicina y Biotecnologia of Cantabria, Santander, Spain, 2017. Dr. Federica Bertocchini is an Italian researcher working in the field of Developmental biology and, as a hobby, she is keen on beekeeping. One day, while cleaning the bee yards, she removes some larvae of the wax moth Galleria mellonella and she puts them into some plastic bags. In a matter of minutes, she starts noticing little holes in the bags. And it doesn’t take long until she realizes that the larvae are chewing it.

This is how the accidental discovery happened. You have probably already heard of it because in 2018 this story gained wide media coverage worldwide, and now we have reached Federica Bertocchini to gather fresh news on her progress. Here we want to tell you more about them, the project she is currently developing and, as usual, how you can support it.

Plastic waste won’t go away alone (not in the next 1000 years at least)

A reusable alternative to single-use plastic bags. Photo by Madison Inouye from Pexels
A reusable alternative to single-use plastic bags. Photo by Madison Inouye from Pexels

Why is this discovery so important in the first place? Among the different types of plastic, polyethylene (PE) and polypropylene (PP) represent the first and the second-most widely produced commodity plastic, followed by PVC and PET (i.e. polyester, see a previous article we published about Lefrik). PE is the most common thermoplastic and it is largely used in packaging, as, for example, plastic bags. In 2017 over 100 million tons of PE were produced, which corresponded to 34% of the total plastics market (source: Wikipedia).

So how are we dealing with plastic once it becomes waste (which happens at a high rate in the case of PE and PET, being them mainly intended for single-use purposes)?  Global statistics on plastic waste disposal show that in 2015 19.5% of plastic was recycled and 25.5% was burned to produce electricity, i.e. for energy recovery via combustion,  (source: Our World in Data). And what about the rest? By a large percentage, it is discarded in landfills. And this is not good news because the plastic may take up to 1,000 years to decompose, polluting land and water in the process.

This explains why finding a mechanism that is able to quickly biodegrade plastic without leaving a trace of pollutants in the environment is a priority. We have already seen in previous articles how organizations like The Ocean Cleanup and the Seabin Project are retrieving plastic in the open ocean and closer to the coast. Moreover, we have recently posted the news about Carbios, a French company that in April announced the publication of an article on Nature regarding an enzymatic process to break down and recycle, ie. to biodegrade, PET. Federica Bertocchini’s project can be seen as a further step in these directions, as it may provide us with a workable and sustainable option to deal with PE plastic once it has been collected.

How wax worms eat plastic

Wax worms. Courtesy of Federica Bertocchini
Wax worms. Courtesy of Federica Bertocchini

Wax worms are called like this because these larvae’s natural habitat are honeycombs, where they feed on wax. Wax is a natural polymer with a complex chemical composition, but on the whole, it is somehow similar to that of PE, in that both present long chains of carbon-based chemical bonds (the most frequent hydrocarbon bond is the CH2–CH2 both in honeycomb wax and in PE).

And since Galleria mellonella larvae evolved to degrade the chemical bonds of wax to eat it, so they are able to do the same with PE, which they ingest and process somehow, even if both whether they digest it or not, and the exact outcome of this process are still uncertain. As for the latter point, some studies seem to support the idea that the outcome of the process is e.g. ethylene glycol (also informally referred to as ‘glycol’), others to fatty acids or esters.

In April 2017 an article on this topic was published in Current Biology. The paper was written by Federica Bertocchini together with Paolo Bombelli and Christopher J. Howe of the Department of Biochemistry of the University of Cambridge. In the experiment they described, 100 larvae were put close to plastic bags, and in 12 hours they were able to biodegrade 92 mg of PE (even if, again, it is not clear yet whether they were able to properly digest it and, in case, to which extent).

Many questions still need to be answered though. The first is, what allows wax worms to process PE? Are they actually digesting it? And what is the outcome of the process? Furthermore, are they able to break the (otherwise) resilient chemical bond CH2–CH2 using enzymes present in their oral cavity? Or does this depend on bacteria that live in their intestines? Answering these, and more, questions is crucial, especially in light of being able to replicate the process artificially, that is, to achieve large-scale PE bio-degradation. And this precisely the goal of Federica Bertocchini’s research projects.

Plastic Entropy

Plastic Entropy is the name of the initiative under which Federica Bertocchini is working on this research program, which is divided into three projects, that will entail:

  • Identifying the molecular mechanism responsible for the biodegradation of PE, so, again, to understand what allows wax worms to biodegrade plastic;
  • Developing the biotechnology, which means understanding how to replicate the molecules of interest at large scale using genetic engineering techniques;
  • Analyzing the by-products of PE bio-degradation.

‘The plan is surely not to keep millions of wax worms in captivity feeding them with plastic bags’ jokes the researcher ‘Among the other reasons, we should remember that this organism is a pest, after all, a parasite of bee colonies. On the other hand, before achieving a better understanding of the process we cannot exclude that the worms’ feces themselves may contain a certain amount of microplastics. So our plan is to analyze the process and re-create it on a large scale, using the relevant molecules rather than the larvae‘.

At the time of writing this article, the Italian researcher has recently moved from Santander to Madrid, where she based her new lab by the Biological Research Center (Centro de Investigaciones Biológicas – CIB), one of the largest and most prestigious research centers of the Spanish National Research Council (Consejo Superior de Investigaciones Científicas – CSIC). On top of the public funding received from the Spanish institution, Federica Bertocchini could benefit from private funds made available by Roechling Stiftung, a nonprofit foundation set in Mannheim, Germany.

‘Following the wide media coverage the discovery had two years ago, it took some time to find appropriate funding for this research initiative’ claims Federica Bertocchini ‘This is also because a working and profitable technology is not available yet, and we cannot predict when it will be. At the current stage, we need to conduct basic research, to find options for designing and implementing the large-scale process in the future’.

How to support

  • The Plastic Entropy lab was hiring at CIB in Madrid (Spain). All positions are currently already fulfilled, but if you want to take part in the adventure and help to find ‘biological solutions for global challenges’, keep an eye on the openings page.
  • You can support Plastic Entropy even by simply sharing this article on your favorite social networks. Spread the word!

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