It was a warm morning when I was headed home from vacation in the Domnican. My iPod had died and as a result of the lack of entertainment, I took a look out of the bus’ window. A clear blue sky, beautiful healthy trees, and exotic animals all were in view, but something else caught my eye. Plastic. Along the side of the road was heaps and heaps on trash, primarily single use plastics, as far as the eye could see.
This was the first time that I truly noticed the problem caused by single use plastics, but the imapct wasn’t just abroad. During the drive home from Pearson airport I again, noticed plastics along the side of the road. This spiralled into deep research on why we have so much plastic just lying around.
When got home I booted up my computer and started searching. I was blown away - there’s around 8 billion tons of plastic in the world right now, and only 9% of it gets recycled. That means that approximately 7.2 billion tons of plastic around the world isn’t getting recycled. So where does it go? 79% of it ends up in landfills or somewhere in the environment (most often, the ocean). Due to all this plastic, ingestion, suffocation and entanglement affects hundreds of marine species. Now, it’s common for fish to contain mercury, dioxins, plastic compounds, hexachlorobenzene and PCBs (heavy metals). This eventually makes it up the food chain affecting humans. Even with all of this damage to nature, the amount of plastic in the world isn’t going down. Currently a garbage truck worth of plastic is being dumped into the ocean every day. It makes no sense to continue harming the planet we live in, why would you not recycle? Turns out, it’s because there’s no money in recycling plastic. Since it isn’t of “virgin quality,” no companies or countries will buy it because it isn’t pure enough and it’s too dirty.
So, what if there was a way to completely break down plastic in just a fraction of the time, converting it to its monomer form at a quality that would seem brand new?
In 2016, researchers from Japan’s Kyoto Institute of Technology collected 250 PET-contaminated samples including sediment, wastewater and soil from outside of a PET plastic recycling plant and screened the microbes that thrived on the samples. They found a bacteria known as Ideonella Sakianesis, which is capable of breaking down and consuming the plastic polyethylene terephthalate (PET) as its sole carbon and energy source.
Through tests, the researchers discovered that a thin film of PET can be broken down over the course of 6 weeks provided that the temperature is maintained at 30 degrees Celsius by a community of Ideonella sakainesis.
In the coming months, the researchers were able to successfully confirm the presence of a certain protein known as PETase that is synthesized by the bacteria and gives it its plastic eating capabilities. PETase has been seen to secrete two additional enzymes known as MHETase and BHETase which breakdown the polymer bonds into smaller monomers.
The PETase breaks down PET into two hydrolyse MHETase and BHET and the MHETase further breaks that monomer down into TPA and ethylene glycol.
The current byproducts in of PETase and PET degradation are glycol and TPA. Glycol has seen to be a common by product in the degradation in the plastic eating waxworm and mealworm, thus it would be safe to assume that we can expect some, if not most of the product of breaking down PE and PS to be glycol.
Even this these amazing scientific discoveries, there has been minimal effort in solving this issue. Currently, the main competitor in the market only recycles 110 kg of plastic a day, which equates to about 40 tonnes of plastic in a year for the entire company. This is even close enough to solve this problem.
This is where we come in with our moonshot company -Ideo. Our solution to this problem revolves around this newly discovered bacteria. By leveraging genetic engineering technologies, we will enable the PETase enzyme produced by the ideonella sakaiensis to accept genes from the bacteria found in the gut microbiome of the waxworm and meal worm, creating a new recombinant enzyme to bind to and break down Polyethylene, Polyethylene terephthalate, and Polystyrene at extremely efficient rates so that we can break down and clean up.
1. Genetic Engineering
Currently, with GE technology, Ideonella sakaiensis can accept Azotobacter sp.’s genes, allowing them to survive in water. This is helps our foundatoin of the moonshot aspect as it shows cross breeding azotobacter and general other bacterial genes into the cells of Ideonella sakiansis to produce desired results is possible. Knowing this, we should be able to translocate the genes from other bacteria into Ideonella.
Finding the gene
Since we don’t know much about the genetic code of the bacteria, we will need to sequence its genome to understand more. Free living bacteria such as our ideonella sakaiensis have 1500–7500 genes, so it won’t cost much do sequence.
From there, we can run a BLAST (Basic Local Alignment Search Tool) query. BLAST is an algorithm used to generate alignment between nucleotide or protein sequence and nucleotide or protein sequences within a database.
As for the edits themselves, CRISPR is the most appealing technology as it has been used countless times for bacterial genome editing, is relatively cheap, and is a technology that is advancing at an extremely fast rate.
There are 2 main goals when it comes to genetically engineering this bacteria and they are as follows: enabling the PETase enzymes produced to bind to and break down other forms of plastic (Polyethylene and polystyrene), and increasing the efficiency of the bacteria.
- We aim to sequence the genome of the bacteria found in the gut of the waxworm which can break down polyethylene plastic (PE), and the bacteria found in the gut of the mealworm, which can break down polystyrene plastic (PS). Follow a similar process as done to the ideonella sakaiensis, we will end up at a specific gene in the bacteria’s DNA and insert it into the ideonella sakaiensis. From there, we will insert the target gene into the ideonella and expect the bacteria to produce a new recombinant enzyme to work on not just PET but PE and PS as well. In this paper, it was proven that recombinant enzymes can be expressed in one bacteria, providing that it may be possible to create a “silver bullet” enzymes to target all types of plastic.
- Increasing the efficiency of the bacteria can be done in different ways: by overexpressing a certain gene responsible for its efficiency by using a promoter, a sequence of DNA needed to turn a gene on or off, or with multiple copies of the gene. At the same time, we can target and remove any unnecessary genes that may hinder its efficiency.
2. Bacteria Growth
Once we have this mutated bacteria, we will need to produce vast amounts of it to break down the seemingly infinite amount of plastic on earth.
To scale up production of this bacteria, we will culture it in a bioreactor.
A bioreactor is an apparatus that provides a constant, homogeneous environment by constantly stirring the contents and controlling different growth factors.
There are many different types of bioreactors, each are best suited to different situations. For our solution, we will be using a stir tank bioreactor (STR).
The STR offers many advantages that align with our vision including:
- easy to scale up
- good fluid mixing and oxygen transfer ability
- ease of maintaining homogeneous conditions
- existing industrial infrastructure (minimal development costs)
- proven performance
- easy compliance with cGMP requirements (Current Good Manufacturing Practice — regulations enforced by the FDA assures proper design, monitoring, and control of manufacturing processes and facilities)
- The main drawback of STRs are its high power consumption — we can use the ethylene glycol as a source of fuel to power the bioreactor to creator a closed loop, net neutral carbon emission system to continuously power our systems with no extra cost / impact.
- pH level — 6.5–7.0. Most bacteria grow best in close to neutral pH values (6.5–7.0), but some may be acidophiles, can can tolerate pH levels as low as 1.0. In some cases, bacteria may produce acid as they grow, lowering the pH in the surrounding environment. In this case, something else must be introduced in the environment to neutralize the bacterial acid or its growth will halt.
- Temperature — it was found that the part of the PETase protein that performs the chemical digestion is physically tailored to bind to the PET surface and works at 30 degrees Celsius. However, the bacteria found in the larvae work best in temperatures of 23 degrees Celsius.
- Adequate fluid velocity and shear stress.
Breaking Down Plastic
Finally, we need a site to release the bacteria to break down the plastic as its byproducts can be harmful to the environment if not controlled.
The hosted bacteria will then be leached into a vat contaning large amounts of plastic which will act as the site of degration degraded.
As the plastic gets broken down, the product will then purified to retrieve the plastic monomers which can be sold for many purposes, including re-production of plastic that we know we can successfully breakdown, creating a closed loop system.
Even though professor Mcgheen, the scientist behind PETase suggested that it should be well within our capabilities to counter multiple different kinds of plastic using a single bacteria, there is currently no research that allows us to pinpoint the gene that is directly involved in the production of PETase, thus hindering any kind of potential for gene editing. That’s where our barrier lies. Any funding provided today will be allocated towards research and development in attempt to locate the gene taking us a step closer to a plastic waste free world.
Our unique approach of teaming up with nature to break down PE, PS, and PET plastic allows us to do so at a rate of 300kg of plastic in 24 hours or 110 tons a year per production plant. At Ideo, we strive to leverage emerging technologies in conjuction with nature to take a step closer to more sustainable, plastic-stable and a healthier environment for not only us, but all other ecological life that share this home with us.