Are plastic-eating enzymes the answer to our pollution problem? – On the Green Fence

#plasticpollution #environment #enzymes #bacteria #upcycling

Episode 3: Are plastic-eating enzymes the answer to our pollution problem?

Each year, millions of tons of plastic waste ends up in the environment where it can last for centuries. Only 9% of it is recycled. But the discovery of plastic-gobbling enzymes has raised hopes of solving this mounting problem.

Biochemist Uwe Bornscheuer and his team at the University of Greifswald, Germany, are working with enzymes that can break down a type of plastic called polyurethane.

It’s a fast-growing area of research around the world. And scientists are not only harnessing microbes to deal with plastic waste. They’re also using bugs to turn plastic into something entirely new, including products we can eat.

But is this biotechnology scalable? And does it make sense from an economic perspective?

Interviewees featured in this episode:

Uwe Bornscheuer, professor of biotechnology at the University of Greifswald, Germany
Jo Sadler, Chancellor’s Fellow at the University of Edinburgh’s School of Biological Sciences

On the Green Fence is produced by DW studios in Bonn, Germany.

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Chapters:

00:00 Intro
04:42 Enzymes evolving to degrade plastics
06:17 Uwe’s lucky find
07:52 PET-eating bacteria
12:06 Downsides, limits and cost
15:59 Enzymatic vs. mechanical recycling
19:01 Upcycling waste
20:06 Turning PET into vanillin
27:47 What role can enzymes play?
32:58 Rethinking how we use plastic

On the green Fence see look at this it’s London in wintertime a plane flight 5100 is approaching Heathrow Airport there’s fog on the ground the crew have been given the all clear to land but as they start The Descent something goes wrong push out ofed mday pressure Mayday emergency in the plane’s left wing

There’s a small metal box containing a mass of wires insulated with plastic and this plastic has started to disintegrate the control function of the Box fails there’s an explosion the plane never makes it to the airport instead it crashes wreaking Devastation on a suburban area in West London all those on board

Perish what went wrong it turns out a mutant bacterium that escaped from a lab infiltrated the aircraft and this Rogue microorganism well it feeds on plastic and eventually the bacterium was able to degrade the plastic and it spread out in London and the while after you had airplane crashes Subways exploded simply

Because the plastic was used for insulation the entire infrastructure in the city starts to break down because so many things are made of plastic and that’s what this bacterium is gobbling up the bacterium was eating the insulation you had a short circuit in the electricity and then U barer is a professor of

Biotechnology at the University of graval in Northern Germany and the Sci-Fi book he’s talking about is called mutant 59 the plastic eaters the book contains a love story and the book also has a good end a happy end it was published in the early ’70s at a time

When public concerns about plastic waste piling up in landfill and in the environment were just starting to emerge the story also featured in the BBC TV show doomwatch that’s what you can hear in the Background more than 50 years on this sci-fi tail perhaps isn’t as far-fetched as it seems okay not the part about bacteria making planes fall out of the sky but plastic eating bacteria do exist and scientists like U believe these microorganisms have a role to play in helping us tackle the plastic pollution

Crisis welcome to to DWS on the green fence I’m Neil King and this is episode three of our series about Plastics a material made from fossil fuels that is essential for Modern Life but our failure to manage it sustainably has led to a massive problem around 430 million

Tons of plastic are produced every year and only a tiny share of that just 9% is recycled More Than A Fifth ends up as litter and because it’s so durable when it lands in nature in rivers in oceans in soils it can endure for centuries but what if we could engineer bacteria to

Decompose it on a large scale or to break it down into its original chemical parts so that it can be recycled every barrel of oil we don’t need to use in the future to make Plastics is good for the environment I think it’s clearly a game Cher and we have to think about

Different types of plastics we target scientists are not only harnessing microbes to recycle Plastics in this novel way they’re also employing bugs to turn plastic into something totally new and converted it into the compound called vanillin and vanillin is um an interesting molecule it’s responsible for that very characteristic smell and

Taste of vanilla and what we might put in our cakes or ice cream or whatever sounds crazy right but in this episode we’ll be taking a look at these tiny plastic eaters and whether they might be able to help us deal with the mounting waste problem is this biotechnology

Scalable does it make sense from an economic perspective and what would it mean for climate change all around us there are microscopic creatures working to break things down these microbes such as bacteria and fungi have evolved powerful enzymes to biodegrade stuff in their environments think of leaves on the

Forest floor dead animals food scraps but what happens when there’s a new man manmade material that these bugs don’t know how to deal with such as plastic on a chemical level Plastics are polymers that means they are made up of long chains of smaller molecules called monomers these strong chains are

Produced by refining fossil oil or gas and then converting it into monomers in a process involving extremely high temperatures the reason plastic doesn’t biodegrade in nature is that the enzymes in most microbes simp simply aren’t equipped to attack the strong chemical bonds of these man-made polymers but there are signs that this

Is changing get this because there are millions of tons of plastic ending up in the environment each year certain enzymes are evolving to break this material down and some bacteria are even using it as an energy source or as food to grow which from an evolutionary point

Of view makes a lot of of sense because if all the other microbes living together with you can only eat sugar or protein or fats and oils and you are the only guy who can eat the plastic you have a huge Advantage yeah because if there is no normal food available you

Can still grow biochemist U borer and his team at the University of grial have discovered three enzymes capable of breaking down plastic they were looking in the soil at the site of a company that produces polyurethane a type of plastic used in things like mattresses insulation in buildings and running shoes and well

These enzymes that they found had adapted to degrade that particular type of plastic they were exposed to it was a lucky find this is a little bit like playing Lottery yeah the chance to become a millionaire is very little we played more or less the same game hoping

That we can find these unique enzymes especially in that soil which was contaminated with poly orane over the decades and maybe M organisms adapted to it each year around 25 million tons of polyurethane are produced that’s a little over 5% of global Plastics and it’s difficult to recycle so roughly 2/3

Of polyurethane that’s thrown away ends up in landfill or is incinerated for energy the chance for success is very little to find novel enzymes which can degrade poly Oran which is a compound made by chemists a very complex polymer and very difficult to digest it’s not so

Easy to degrade by natural enzymes or microbes because it’s a chemical bond which hardly ever occurs in nature and that is why it’s so difficult to find enzymes which act on it Research into plastic eating enzymes is a fast developing area but things in the field only really took off after 20

16 when a team in Japan found a neverbe identified bacterium in a waste dump that consumed plastic as a source of food the bacterium was called ideonella sensis and it contained two enzymes that could slowly break down P or pet this is the plastic used to make drink bottles

Clothing and packaging by the way to be clear when I say that the bacteria breaks the plastic down I mean that they degrade pet into its chemical building blocks also known know as monomers in the case of pet the monomers are taric acid and ethylene glycol so about 70

Years after the first pet was synthesized by a chemist in the US um this Ella zaken strain was able to adapt to this new carbon Source but naturally occurring enzymes capable of attacking plastic are slow and so far they’ve only been shown to work on some types of

Plastic like pet and polyurethane and often only certain conditions and temperatures so over the past few years scientists have been genetically modifying them in the lab to turbocharge their performance and make them more robust in the meantime different plastic degrading enzymes have been discovered in worms in cow’s stomachs and in fungus

So what does all this mean could it help us tackle the plastic waste problem could we at some point release these engineered bugs into the environment so they can Chomp through the plastic piling up in landfills for instance it’s a question that U gets a lot can we

Make a microorganism which we throw in the ocean which eats the plastic and things like that besides the fact that there are 10 different types or 20 different types of plastics and you need 20 different microbes and besides the fact that this is hit because this is a genetically modified organism you are

Not allowed to throw into the ocean uh the problem is it would be completely out of control and you don’t want to have your window frame falling out of your window because certain bacteria can eat your window frame yeah or or your car car or your Sailing

Boat yeah so uh I think it’s better if scientists like me and others uh try to develop methods enzymes engineered microbes to use them in a factory where we collect the plastic pieces of course the consumers like you and me we have to make sure that we separate the Plastics

At home at least Plastics from other dirt and waste that this goes to a factory which can say Okay pet this line nylon that line polyan that line polystyrene over here and then we have ways to solve the plastic problem but that’s something over that’s never even

Occurred to me that it means that in a way that if you had these operations and you developed an enzyme that was really really super efficient you’d have to be very careful and keep it contained right yeah for the enzyme alone it doesn’t matter because the enzyme cannot do much

Outside I mean if I throw my enzymes into the Baltic Sea next to gide the microbes living in the water will just eat it but if you throw in microbes intact microorganism they can of course divide and become more and more microbes and then you have then then it’s out of

Control So the plan would not be to release these enzymes into the wild and let them clean up rather they’d be put to work in a controlled environment like a big Factory where they could break down Plastics into their chemical building blocks their monomers and these building blocks could then be used to

Make plastic that is essentially as good as new the major plus with recycling in this way is that you can produce virgin quality plastic without getting more fossil fuels like oil and gas out of the ground and reducing Reliance on fossil fuels is crucial when the plastic

Industry is trying to bring down its CO2 emissions we mustn’t forget that it’s an industry with a comparable carbon footprint to Aviation but there are some big downsides and limits much of the work on enzymes is being conducted on a small scale by scientists in their Labs

Like over and for this process to play a serious role in plastic recycling it would have to be dramatically expanded W thinks it’s only a matter of time before that happens I think it’s clearly a game Cher and we have to think about or have to discuss different types of plastics

We target currently all polymer are made by chemical methods so pet is made from talic Acid produced from Petrol and it’s made from ethylene glycol and you can isolate this and then you can make a new polymer without the need for petrol again so this is true recycling what

Would you say are the challenges that would you know hamper this from being used on a larger scale from you know up scaling this and um really going at this on an industrial level we now have shown the first three enzymes which are different in their action so one has to

Pick the best one and then we have to use our protein engineering methods to make the enone more active more stable produce it on large scale and not only in the academic scale in my lab and then you need the real engineers and the company who builds a factory and

Develops all the process details so a time frame of 5 to 8 years is I think quite likely to establish such a process at least for the major poly Oran because if you have different starting materials mattress insulation material your old running shoes you have to maybe adapt your process for the

Different quality of the materials but I think um it’s not it’s most likely that this can be developed yeah and I mean what could you tell us about how I mean how energy intensive would this be and how fast could they actually break it down if you you could I don’t know are

There any calculations on that if you wanted to break down a ton of polyure I I I simply cannot tell because we have done this on small scale it will not be cost efficient for sure yeah so it must be a process where you at least convert 10050 200 gram of starting material

Pooran waste per liter within a time frame of half a day um and then you should be in a Range where it can become attractive for a company to invest into this process of course I don’t have this company so I rely on our industrial partner that they push this

Or other industrial other companies go for that and develop a process for poo wasain but I think we don’t have to wait 20 years for that our scientists have created a one-of-a-kind enzymatic process that allows pet the world’s second most commonly used plastic to be biologically recycled unlike conventional recycling

Processes our revolutionary approach returns to the fundamental components of pet it allows all a French startup called carbios has already made big steps towards deploying enzymes for recycling plastic on an industrial scale and it’s got major companies like L’Oreal Pepsi Co and Nestle on board as partners our teams have also developed

An enzymatic additive that accelerates the biodegradation of pla Cabos is building the world’s first biological recycl plant in northeastern France with the goal of being up and running by 2025 the company says its new plant will be able to process 50,000 tons of pet or pet waste per year for comparison more

Than 70 million tons of pet is produced annually around the world CIO says its bioreactor and genetically modified enzymes can degrade the equivalent of 100,000 pet plastic bottles in 10 hours but what’s the catch Well at the moment this process uses a lot of energy mainly because the plastic waste has to be pre-treated so that the enzymes can break it down that will likely improve as enzymes are engineered to be more efficient and can function at room temperature that would save energy

Costs but right now the process has a higher carbon footprint than traditional recycling or mechanical recycling mechanical recycling is the most popular way to recycle Plastics it involves washing sorting and grinding down plastic waste into pellets to produce new plastic the downside here is that the quality of the material takes a hit

After each cycle which means it can only be recycled a limited number of times but Studies have shown it scores best in terms of emissions and climate change impact Enzyme-based recycling can be energy intensive but in theory it’s still uses less energy and releases less emissions than producing virgin pet from fossil fuels according to the US national renewable energy laboratory and the quality of the plastic is just as good so that it can technically be recycled

This way an infinite number of times every barrel of oil we don’t need to use in the future to make Plastics is good for the environment whether during the process of converting petrol into a certain polymer you produce of course carbon dioxide or carbon dioxide equivalent this can be avoided when you

Burn the plastic later on uh instead of recycling you again produce carbon dioxide so every barrel of oil we can avoid because we use less plastic don’t use single plastic or have an intelligent way to recycle plastic and weuse it And what about the cost well virgin plastic is far cheaper to produce than pet that’s been recycled with the help of enzymes a study by the US national renewable energy laboratory estimated that pet monomers produced with enzymes can cost up to twice as much as virgin fossil-based monomers this can change

For example if the oil price goes up or down and the competitiveness of recycled plastic could also shift if if more ambitious targets for curbing plastic waste or emissions are adopted while we’re speaking about cost there could also be a strong economic incentive for improving the way we deal with plastic

Waste plastic packaging loses 95% of its material value after a single use costing the global economy billions each year and recycling could be lucrative if it were possible let’s say to take a water bottle in landfill and make it into something more valuable A lot of the work that had been done before I started working on this had treated plastic very much as something that could be perhaps recycled into more plastic um but I I started thinking about this I thought well actually that’s not really in in the longer term

Of things are still going to be plastic the end of life and it’s still got potential to be a pollutant so what I was interested in was actually degrading the plastic into its constituent parts so the building blocks that make up this plastic if we can break it back down

Into those building blocks can we then actually at a chemical level modify those building blocks and convert them into something totally different Joe Sadler is a Chancellor’s fellow at the University of Edinburgh in the UK and her research focuses on using biological systems to upcycle waste plastic into useful substances that would otherwise

Be produced directly from oil she genetically engineered the bacteria eoli to create something from plastic that we can Eat and so the way I wanted to demonstrate this was by converting uh pets at polyethylene carate and that’s the plastic that plastic bottles are made out of for example a lot of food packaging um I wanted to break that plastic into its constituent um Parts

Which we call monomers and I took one of these monomers and converted it into the compound called vanillin and vanillin is um an interesting molecule it’s responsible for that very characteristic smell and taste of vanilla and what we might put in our cakes or ice cream or

Whatever and um by doing just four chemical modifications catalyzed by B by an engineered cell um we could actually convert this plastic degradation product into this um ice cream or food flavoring molecule um and so for me this was a really exciting proof of this concept that we can actually start thinking

About plastic waste as a resource and we can start using it as a feed stop to make other chemicals but how I mean how did that idea come about because that sounds like I mean to me as as a Layman who has no idea about any of this it it

Sounds crazy something that you put in cake can and and you take you take pet you take a plastic and you can turn it into something that we can actually eat I mean how did you it seems like were you eating a piece of cake when this

Idea arose or how did this happen no I wish I wish um no so this comes back to my background in chemistry actually I was I remember very clearly sitting at my desk one day thinking about what I wanted my research to go in the future and I’ve always had this fascination

With plastic and and thought that it’s so many inefficiencies in its current life cycle and I actually just looked up the structure of pet plastic and I started drawing out chemical structures and I used my knowledge of chemical modifications of chemistry basically to think well if that’s the

Starting material what can we do to that molecule chemically um and then looked at what we could do to it and then found out that that you know with with the help of looking into the literature found out that actually with four simple steps we could convert that chemical

Structure from the degradation PL of plastic into the chemical structure of of vanillin and it is you said the chemical structure it’s identical so this would also taste the same you could actually put this in your cake and it would be exactly the same there wouldn’t be any difference that’s exactly right

So theoretically And I stress this is theoretically because this still very early research we’ve got a lot of work to do before we can get to this point but theoretically you could make the vanillin at a at a high scale and purify it um away from all the the other stuff

That’s in the reaction mixture um that villin would be chemically identical to the villin that you would currently buy from the petrochemical um based industry and that’s because it’s precisely the same molecule the the vanilla that you get from natural sources so extracting it from the vanilla plant which actually

Actually accounts for less than 1% of global demand um that actually has other small low-level impurities present in it and this gives the natural FineLine a slightly more full bodied and rounded flavor profile than the chemically derived vanillin what is the the kind of

Ratio Joe you know I mean if you were to take I don’t know I mean I’m just guessing now you took a ton of of pet uh plastic I mean how much vanillin would you get out of a ton of you know if you go through the process we’re working on

Very small scales at the moment so if you it’s hard to say from a ton of pet the conversions from the pets actually quite High that’s not the problem the problem is more that we can’t have very high concentrations of pet in our reaction so you need a huge huge volume

In order to process a ton of pet you’d need a an absolutely vast volume of of cells and of um your reaction to actually convert all of that so you if if you had the capability to convert a ton of pet we’d probably get out quite a

Lot of vanilla maybe like half a ton of vanillin but we’re not at the stage yet where we can go anywhere near that scale because the volume of reaction we’d need to do and the volume of biomass we’d have to create in order to catalyze that

Reaction mhm and the reaction I mean the conversion process that is being driven by bacteria right that’s right yes so what we did is we we took some um strain of EA which is used a lot already in industrial biotechnology and it’s a strain which is is always held within

The laboratory it’s nonpathogenic so it’s not going to cause any um threat to human health and what we did is we um fed it some DNA which encodes uh the genes which will make the proteins that will do the chemistry so we designed we looked in the literature we found the

Enzymes which we know can catalyze these reactions that will convert the plastic into the minin and then we uh designed DNA to to tell the bacteria to make those proteins and then we inserted that into the bacteria themselves you can then feed the bacteria chemical which basically says to them start making

Those proteins and you can hijack the cells native metabolism and cellular Machinery to actually um start making these sort of nonnative proteins um and at that point you can feed in your plastic degradation product it will take those molecules using those proteins that they’ve expressed and convert it

Into vanilla are there any other chemicals that you know might be possible to create from this process or is this just limited to vanillin no absolutely there are many different chemicals that you can create from from a very similar process so that the type of chemical that you create is

Dictated by the enzymes that you you tell your cell to make so if you tell your cell to make a different set of enzymes it will then um proceed through a different chemical pathway and make a different molecule so what my my own team and other teams in the field doing

Now is is doing just that so they’re building lots of different Pathways using lots of different enzymes to actually convert this plastic waste into a whole range of different products um and we’re seeing um yeah many many different things coming out now so it’s really exciting for the field and it’s

It’s really exploded now and people are really beginning to see this as a resource yeah it sounds like a really exciting well kind of jigsaw puzzle I guess in a way put putting together a lot of interesting pieces and and and experimenting but I mean it would it be

Also possible to apply this process to um you know if we took other types of plastics you know besides pet you know for instance Plastics that are more difficult to recycle yeah that’s a great question um the pet is what we in the field we just describe it as the low hanging fruit

That we like pep because it’s it’s relatively easy to break down into very um uniform and predictable building blocks and it always breaks down into the same thing and this makes it quite easy to upcycle because we always know what we’re starting from um and so most

Of the work to be that’s been done to date focuses on pet for that reason a much bigger challenge in the field is looking towards other other Plastics because they’re much much harder to break down so pet is linked by um what we call Esta Bond it means it’s got a

Carbon oxygen linkage in the backbone chain and this makes it this is like a sort of handle that things can attack when and break it down but some Plastics are solely linked by carbon carbon bonds in the backbone polymer chain um and there’s no there’s no sort of chemical

Handle that you can really attack and target for degradation and this makes them really difficult to degrade um so the degradation of these Plastics is still an outstanding challenge I mean given the sheer amount of plastic waste that we have I mean it’s it’s hundreds and millions of of tons globally right

Um plastic waste that we’re grappling with every year I mean how big a role do you think can enzimatic recycling or app cycling actually play and you know will it become more important in the long run than mechanical recycling in your opinion yes this is a really plastic

Pollution is as you say it’s a very big problem and it’s a very complicated problem and I don’t think there’s a sort of one siiz fits all solution and this the problem is being already tackled from people from all sorts of different backgrounds from chemists bi and biotechnologists mechanical engineers

People in policy um you know it’s a really multi-dimensional set of solutions which we’re trying to develop to to tackle this problem I think biological degradation up cycling is a very important part of that toolbox and I think there are situations where it’s really well suited biological Solutions

Will only be useful and competitive if we can overcome the scale issues that we currently face um and that’s a really big challeng for us at the moment if we look at the actual process I mean getting these things scaled and off the ground it requires also I would assume a

Collaboration um you know and and and consultation with policy makers um I mean how closely do scientists cooperate or collaborate with policy makers on this plastic waste issue there is collaboration it’s something that um I’m actually hoping to get more involved in it I haven’t done so much of it yet but

It’s it’s certainly an area which I think is extremely important as you say because it’s it’s got to be there’s got to be cross talk so that we can actually turn these Technologies into a reality um it’s beginning to creep in to to policy but uh it’s quite slow progress

And I think actually getting scientists into the room where policies are being developed and laws are being um sort of developed if if you like is quite difficult and they’re still being sidelined I think in favor of perhaps people from the oil industry and and Industry representatives and I think

There needs to be more emphasis on including the scientists actually developing these Technologies into those conversations as well I mean if you had a wish list I mean what would you like to see in terms of Regulation and incentives to push things in a different direction if you

Could just you know formulate three key things that would really help you get things started and off the ground so I think I’d like to incentivize designing kind of consumer products for circularity so they need to be designed to be disassembled or or um recycled efficiently as possible but

Actually you know I guess in the context of circular economy recycling is actually quite far down the list of desirable things so obviously reducing usage in the first place is the most important thing and then reusing it where possible and then comes recycling but you know yeah we need to incentivize

This idea of treating these waste products as as a resource and make it easier for people to to recycle them so making recycling schemes more transparent uh but also you know actually some you know it shouldn’t all be on the consumer to to make the right decision and I think really it’s it’s

The responsibility of the producers of a lot of these products to make it very easy to do this and to not mix different materials in a single product which makes it impossible to recycle um yeah so just just to simplify the the packaging as much as possible and to

Make it easy to degrade Joe final question um what are the next steps what are your plans uh for the future what’s next so what I’m hoping to do next is actually tackle these sort of less easy to degrade plastic so the non- hydrolized ones that I touched on

Earlier um I think pet that we have we we’ve demonstrated that we can convert pet into vanillin and that’s I think great proof concept for the field but now we need to move on to the sort of the real challenge which is degrading all sorts of plastic waste so polyethylene polypropylene polystyrene

Into predictable um mixtures of degradation products and then start thinking about how we can upcycle those into useful products U and but until we can really tackle these non-hydrolyzable Plastics which actually account for nearly 65% of all plastic waste I still think we’ve got a lot of work to be done

So it’s it’s an exciting time for the Field many thanks to Joe Sadler from the University of Edinburgh There new enzymes that can decompose plastic are being discovered all the time from the Arctic to the Alps a global study from 2021 found 30,000 different enzymes in the environment that could degrade 10 types of plastic findings like these grab headlines and public interest perhaps because of the hope they offer

In finding a solution to the plastic pollution problem but what they also highlight is the impact our dependence on plastic is having on the environment the fact that microbes are adapting to plastic because it’s everywhere work to harness their potential is advancing rapidly but as we’ve heard from U and

Joe enzymes can only be part of the solution we can’t rely on them to deal with all our plastic waste and there are some significant limitations enzyme based recycling will only play a role if the process can be scaled up and if it’s able to compete on cost and carbon fo

Footprint with other forms of recycling as far as AA is concerned the priority should be to rethink the way we use plastic and to prevent it ending up in the environment in the first place so I think for different polymeres there will be different solutions for recycling I think the most important

Message is we should avoid single-use plastic because this harms the environment mostly and for the other Plastics which we use to construct houses or which are used in cars and ever we should ensure that we have a intelligent labeling system so that we can recollect and sort them better than

We do it now plastic materials have many advantages and they are durable I mean you can use them a 100 years in many cases so we should not forget that plastic is not bad we just have to make sure that we use it properly and especially discard it

Properly and that soundbite from U baronshire bringings us to to the end of this week’s episode in the next episode of our plastic series we’ll be taking a closer look at bioplastics today we have all kinds of different bioplastics which are perfectly able to substitute conventional Plastics and they have

Quite a few properties which make them better than the conventional ones SE is very abundant um so compared to other types of kind of like biomass crops uh we have uh something that’s not going to compete with with food which is really great compared to the first generation

Of bioplastics I hope you’ll be joining us again for that many thanks to my colleague and producer Natalie Mueller and my sound engineer G gari and a big thank you to all our listeners for sharing reviewing and subscribing to on the green fence my name is Neil king take it easy and take

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