If you sit someone down, and explain synthetic biology to them; how you can make microorganisms produce, degrade or detect things, and you ask them to come up with how to use that to solve world problems, there are a few answer that almost always come up. When you start up an iGEM, this is essentially what you do; you ask a group of people, most of them new to synthetic biology, to come up with a useful application of synthetic biology. Things like “make bacteria degrade oil from oil-spills”, or “make bacteria produce pharmaceuticals” or “detect disease” are definitely in the top 5.
Another topic that is almost always suggested is the issue of plastic. We all know that plastic pollution is a major issue; the oceans and landfills are filling up with plastic bags and straws and other junk, and yet we keep consuming and discarding massive amounts of plastic. So why not make bacteria that can degrade these plastics? Or, why not create bacteria that can produce environmentally friendly, biodegradable plastics?
If you google “iGEM plastic”, you can see just how many people have shared these very same thoughts. And yet, we are still drowning in plastic.
As we mentioned in our previous post about iGEM, one issue is that when you attempt to finish a full synthetic biology research project over just a single summer, you often find yourself not actually finishing. There are many teams that have design concepts of bacteria tackling the problem of plastic (Stanford 2009, UCL 2012, Sonyeodul 2016, Baltimore 2017 etc.) , there are many biobricks (standardised genetic parts) created by iGEM teams trying to solve the plastic problem, but there is no team yet that has actually developed an actual, working solution.
Bio-degradable plastics, and bacteria degrading the non-degradable
When it comes to scientifically dealing with the plastic problem, there are essentially three strategies; Bioplastics, Biodegradable plastics, and engineering bacteria capable of degrading the non-degradable.
Traditional plastics are long chains of carbon-molecules, created from petroleum. The problem with these plastics, is that they are made to last, for a long, long time, and they do not degrade in the environment at all. This is why they clog up nature in general and oceans in particular. Because these plastics are entirely man-made, and have never existed in nature before, there are no microorganisms who have developed a method for degrading, and essentially eating, these polymers. They just accumulate. They do degrade slowly, due to UV-radiation from the sun, but takes hundreds of years. Furthermore, since plastics are made from petroleum, they are using up non-renewable resources. Bioplastics are a solution to this, since they are plastics made from things like biomass, like corn. Because they are made from different starting materials, the bioplastics behave differently, and degrade in UV faster than petroleum plastics. Much like with biofuels, there has however been critique against bioplastics, as some say this uses up land that could be used to grow crops to feed people, rather than growing crops to make plastic.
Carbios is a synbio company who have taken the production of bioplastics and turned it from a chemical process, into a fully microbial process. They have engineered microorganisms to make them fully capable of turning biomass into bioplastic. Carbios claims that this process is cheaper than the chemical equivalent, which is significant as most bioplastics are more expensive to produce than petroleum plastics, making them a more expensive and less attractive option to many manufacturers.
The second strategy is biodegradable plastics, which are made by the addition of certain chemicals to petroleum plastics, in order to make them degrade faster in nature. These biodegradable plastics are however not degrading by microorganism, but again, by for instance UV-radiation. The fact that even these bioderadable platics are left in landfills, compost, or on the ocean-floor where there isn’t much sunlight is one of the critiques of biodegradable plastics.A study by Cornell University found that biodegradable plastics, over a period of 3 years, didn’t degrade any faster than “classic” plastic at all. Another critique is the fact that the chemicals added to make the plastics biodegradable make them harder to recycle, and recycling is currently one of the most sustainable ways of keeping plastic out of landfills.
The third, and most synthetic biology solution, is to engineer microorganisms to make them capable of degrading the non-degradable. Lots of iGEM teams have attempted this feat. This strategy involves designing enzymatic pathways capable of degrading the plastic-polymers, and introducing them into microorganisms like E.coli, designing bacteria that “eat” plastic, and converts it into biodegradable monomers. P4SB is a company that have taken this approach a step further than any iGEM team. They are using enzyme-engineering to develop enzymes capable of degrading PET plastic, enzymes which they aim to put into bacteria. Further, they are also engineering and optimizing another bacteria which will degrade the resulting monomers, creating a two-step approach to turning non-degradable plastics into harmless by-products.
University of Edinburgh iGEM team is turning whiskey into plastic
The core-team here at the Synbiologue all attended University of Edinburgh, and so naturally, we are very interested in what the UoE iGEM team is up to. And this year, they are tackling this classic iGEM question of how to solve the plastic problem. They have chosen the Bioplastic-tactic, and have designed a bacteria, like Carbios, which produces plastics from biomass. Unlike Carbios however, they PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) instead of PLA. And because they are a Scottish team, rather than using just any biomass as a starting material, they coupled up with a local Whiskey-distillery, and used bio-waste from whiskey production instead. Not literally Whiskey into plastic, but close enough.
Is synbio the best solution?
It is thrilling to think of all the cool things that synthetic biology can do, but at the end of the day, you still have to ask yourself if it is the best solution. Much like how GMOs are a good solution for increasing the production of food to meet the need making microorganisms that make and degrade plastics are good solutions. But the fact is that we don’t need to increase the amount of food produced in the world; we need to change how it is distributed. There is enough food, it just doesn’t reach the people who need it. In the same sense, we don’t need to find better ways of making or degrading plastic; we need to stop using plastic. (Although, even if we stop using, we still need to degrade the existing plastic, so maybe the degradation is still a good solution, but not without the decrease in plastic use.)
There has been a trend of restaurants banning plastic straws, and stores charging you for plastic bags, but is that enough? And is going to continue, or is it just a trend? At the same time, you also see grocery stores wrapping bananas in plastic (as though they didn’t have any form of natural protective shell) and the sue of plastic in the world is still increasing. Personally, I think that the best solution is to use far less plastic. But I think the reality is that that won’t happen anytime soon. So while we try to work towards a world without mass-consumption of plastic, synbio-plastics are a useful intermediate.