Will microbes bring an end to the plastic disaster? The answer could be an artificial microbe that feasts on plastic
Ongoing lab studies were promising enough for Colossal Biosciences to support a Harvard team to work towards developing X-32 to address the plastics crisis.
What if there was a way to deal with millions of tonnes of legacy plastic waste lying in the oceans, rivers and forests? Science fiction? A team of scientists are, in fact, attempting to solve this massive crisis. Lab results are promising but a fully designed solution is a long way to go.
The world produces some 430 million tonnes of plastic per year. Around 11 million metric tons of plastic currently enter the ocean, and that volume is expected to triple in the next 20 years.
Worryingly, a plastic grocery bag was found in the Mariana Trench — the deepest point in the ocean, according to the United Nations. There is now a marine ecosystem called the “plastisphere”, which comprises the microbial community on plastic debris. Microplastics are ingested and inhaled by humans and animals every day. The annual social and environmental costs linked to plastic pollution are high with some UN estimates suggesting it's more than $1.5 trillion per year.
The experiment
Against this backdrop, and searching for a sustainable way to mitigate plastic pollution, a team of geneticists at the Harvard Medical School has been working to understand whether microorganisms have evolved the basic ability to break down different hydrocarbons or plastic.
Sukanya Punthambaker, co-founder of Breaking, a recently launched plastic degradation and synthetic biology company, has been working on this challenge at the Wyss Institute at Harvard University.
Punthambaker was working with renowned geneticist, George Church (also co-founder of Breaking) when she was able to create X-32, which has the potential to degrade up to 90% of polyesters and polyolefins in less than 22 months — untreated, some of these plastics would take over 80 years to decompose naturally.
Lab studies are still underway and the team is yet to publish their results but initial findings were promising enough for a US-based "de-extinction company" Colossal Biosciences to support the Harvard team to create "Breaking". The aim: To work towards developing X-32 to address the global plastics crisis.
In lab tests, X-32 has started to break down paint brush bristles, fishing wire and dental floss, according to the team at Breaking.
"Here we are leveraging biotechnology and synthetic biology to tackle the huge global plastic pollution problem. What we discovered at the Wyss Institute is that having been helped by Colossal as well, we have found a novel microorganism that can degrade different kinds of plastic. So, that is how we differentiate from other existing technologies,” Punthambaker said.
“We are working towards supercharging these microorganisms so that we can increase their plastic degradation efficiencies. We call them X-32. We will be super-charging them, meaning we will use genetic technologies to enhance and up-regulate their genes that are responsible for the plastic degradation," Punthambaker said.
Earlier efforts
This is not the first time that scientists have found that certain microorganisms have the potential to degrade certain types of plastics. "There was a very famous science paperback in 2016 that showed that microorganisms can degrade PET (Polyethylene terephthalate)," said Punthambaker.
In 2016, a paper by Kyoto Institute of Technology found that by screening natural microbial communities exposed to PET in the environment, they managed to isolate a novel bacterium, ‘Ideonella sakaiensis 201-F6’, which is able to use PET as its major energy and carbon source. When grown on PET, this strain produces two enzymes capable of “hydrolysing” PET. Both enzymes are required to enzymatically convert PET efficiently into its two environmentally benign monomers, which are molecules that make polymers.
Now when Punthambaker looks back she remembers...."I was always interested in nature and science. A lot of my paintings won the first prize at ISRO (Indian Space Research Organisation) in Bengaluru. I was always passionate about it. I am very excited to use all my skillsets in solving such a transformational challenge facing the world now," she said.
Punthambaker did both her undergraduate education and masters in microbiology and biotechnology from Bengaluru and then moved to the University of Michigan for her PhD in molecular biology. Thereafter she joined Church and has been working with the team at Wyss for the past 10 years.
"There have been discoveries that microorganisms can degrade certain basic types of plastic like PET. But no microorganism has been found or created to degrade the really difficult, carbon-to-carbon bonds of certain types of plastic that do not degrade for thousands and thousands of years,” said Kent Wakeford, co-founder and executive chairman at Breaking.
“These include nylon which is in fishing nets, the plastic used in plastic bags at grocery stores, and a lot of plastic that is filling up landfills, oceans, and rivers. That is one of the toughest plastics to break down. That’s the discovery that Sukanya made; so, this is a breakthrough in terms of scope and magnitude," Wakeford said.
The Breaking team believes that the technology is ecologically safe because they are looking at a two-pronged approach. "Safety is our top priority. We are using a two-pronged approach. One is to extract the enzymes responsible for this degradation and that could be separately scaled up as well. So, the answer is that the use of this microorganism to degrade plastics is completely safe," Punthambaker added.
The salient features
"One of the things which is quite amazing about this discovery is that these microorganism needs water and a little bit of salt to survive on carbon. It doesn’t need any type of pre-treatment. It is designed in a way so it can be deployed anywhere. The by-products once it has broken down the plastic, is water, a little bit of CO2, and a little bit of biomass,” Wakeford said.
“When we think of going to the market, the way it scales up is just like any type of enzyme in fermentation plants. So, it is relatively cheap which is great because as we are facing such a major global problem, we want to be able to use it at scale," Wakeford added.
Possible impact of the technology
On whether such a discovery will take focus away from phasing out plastics or reducing the use of plastics completely in daily life, the Breaking team said their breakthrough will help address the massive problem of legacy plastic waste.
"There are 5,000 million tonnes of plastic in oceans, landfills and rivers. That is not the only issue. There are 400 million tonnes (of plastic) created every year and even with any kind of code to limit plastics, it’s going to take only a small percentage off that,” Wakeford said.
“On top of that, there are contributing factors to a lot of environmental issues with plastic such as with washing clothes, polyesters or anything, the fibres are going into the water system; micro and nano plastics are finding their way not only into the environment but also water, agriculture and now into the human body. Humans are consuming a credit card worth the size of plastic every single month and that will impact human health," warned Wakeford.
“We have entered an era in which our environments and bodies are at risk to micro and nanoparticles of polymers (plastics) that we once trusted. We have also entered an age of exponential technologies in which we can see and seek the nuances and continua of polymers. Harmful-to-helpful is not nearly natural vs synthetic; it depends on size, shape and location of the polymer particles,” Church, mentioned earlier, said.
“For example, polyethylene has the same set of bonds as beeswax, just longer. We are "Breaking" these and reusing the parts in beneficial reconfigurations,” Church, who is also a professor of Genetics at Harvard Medical School and of Health Sciences and Technology at the Massachusetts Institute of Technology, said.