Two young scientists break down plastics with bacteria
February 28, 2013
Once it's created, plastic (almost) never dies. While in 12th grade Miranda Wang and Jeanny Yao went in search of a new bacteria to biodegrade plastic -- specifically by breaking down phthalates, a harmful plasticizer. They found an answer surprisingly close to home.Miranda Wang and Jeanny Yao
- Science fair winners
Miranda Wang and Jeanny Yao have identified a new bacteria that breaks down nasty compounds called phthalates, common to flexible plastics and linked to health problems. And they’re still teenagers. Full bio
Double-click the English subtitles below to play the video.
Miranda Wang: We're here to talk about accidents.
How do you feel about accidents?
When we think about accidents,
we usually consider them to be harmful,
unfortunate or even dangerous, and they certainly can be.
But are they always that bad?
The discovery that had led to penicillin, for example,
is one of the most fortunate accidents of all time.
Without biologist Alexander Fleming's moldy accident,
caused by a neglected workstation,
we wouldn't be able to fight off so many bacterial infections.
Jeanny Yao: Miranda and I are here today
because we'd like to share how our accidents
have led to discoveries.
In 2011, we visited the Vancouver Waste Transfer Station
and saw an enormous pit of plastic waste.
We realized that when plastics get to the dump,
it's difficult to sort them because they have similar densities,
and when they're mixed with organic matter
and construction debris, it's truly impossible
to pick them out and environmentally eliminate them.
MW: However, plastics are useful
because they're durable, flexible,
and can be easily molded into so many useful shapes.
The downside of this convenience
is that there's a high cost to this.
Plastics cause serious problems, such as
the destruction of ecosystems,
the pollution of natural resources,
and the reduction of available land space.
This picture you see here is the Great Pacific Gyre.
When you think about plastic pollution
and the marine environment,
we think about the Great Pacific Gyre,
which is supposed to be a floating island of plastic waste.
But that's no longer an accurate depiction
of plastic pollution in the marine environment.
Right now, the ocean is actually a soup of plastic debris,
and there's nowhere you can go in the ocean
where you wouldn't be able to find plastic particles.
JY: In a plastic-dependent society,
cutting down production is a good goal, but it's not enough.
And what about the waste that's already been produced?
Plastics take hundreds to thousands of years to biodegrade.
So we thought, you know what?
Instead of waiting for that garbage to sit there and pile up,
let's find a way to break them down
Sounds cool, right?
Audience: Yeah. JY: Thank you.
But we had a problem.
You see, plastics have very complex structures
and are difficult to biodegrade.
Anyhow, we were curious and hopeful
and still wanted to give it a go.
MW: With this idea in mind, Jeanny and I read through
some hundreds of scientific articles on the Internet,
and we drafted a research proposal
in the beginning of our grade 12 year.
We aimed to find bacteria from our local Fraser River
that can degrade a harmful plasticizer called phthalates.
Phthalates are additives used in everyday plastic products
to increase their flexibility, durability and transparency.
Although they're part of the plastic,
they're not covalently bonded to the plastic backbone.
As a result, they easily escape into our environment.
Not only do phthalates pollute our environment,
but they also pollute our bodies.
To make the matter worse, phthalates are found in products
to which we have a high exposure, such as babies' toys,
beverage containers, cosmetics, and even food wraps.
Phthalates are horrible because
they're so easily taken into our bodies.
They can be absorbed by skin contact, ingested, and inhaled.
JY: Every year, at least 470 million pounds of phthalates
contaminate our air, water and soil.
The Environmental Protection Agency
even classified this group as a top-priority pollutant
because it's been shown to cause cancer and birth defects
by acting as a hormone disruptor.
We read that each year, the Vancouver municipal government
monitors phthalate concentration levels in rivers
to assess their safety.
So we figured, if there are places along our Fraser River
that are contaminated with phthalates,
and if there are bacteria that are able to live in these areas,
then perhaps, perhaps these bacteria could have evolved
to break down phthalates.
MW: So we presented this good idea
to Dr. Lindsay Eltis at the University of British Columbia,
and surprisingly, he actually took us into his lab
and asked his graduate students Adam and James to help us.
Little did we know at that time
that a trip to the dump and some research on the Internet
and plucking up the courage to act upon inspiration
would take us on a life-changing journey
of accidents and discoveries.
JY: The first step in our project
was to collect soil samples from three different sites
along the Fraser River.
Out of thousands of bacteria, we wanted to find ones
that could break down phthalates,
so we enriched our cultures with phthalates
as the only carbon source.
This implied that, if anything grew in our cultures,
then they must be able to live off of phthalates.
Everything went well from there,
and we became amazing scientists. (Laughter)
MW: Um ... uh, Jeanny. JY: I'm just joking.
MW: Okay. Well, it was partially my fault.
You see, I accidentally cracked the flask
that had contained our third enrichment culture,
and as a result, we had to wipe down the incubator room
with bleach and ethanol twice.
And this is only one of the examples of the many accidents
that happened during our experimentation.
But this mistake turned out to be rather serendipitous.
We noticed that the unharmed cultures
came from places of opposite contamination levels,
so this mistake actually led us to think that
perhaps we can compare
the different degradative potentials of bacteria
from sites of opposite contamination levels.
JY: Now that we grew the bacteria,
we wanted to isolate strains by streaking onto mediate plates,
because we thought that would be
less accident-prone, but we were wrong again.
We poked holes in our agar while streaking
and contaminated some samples and funghi.
As a result, we had to streak and restreak several times.
Then we monitored phthalate utilization
and bacterial growth,
and found that they shared an inverse correlation,
so as bacterial populations increased,
phthalate concentrations decreased.
This means that our bacteria were actually living off of phthalates.
MW: So now that we found bacteria that could break down phthalates,
we wondered what these bacteria were.
So Jeanny and I took three of our most efficient strains
and then performed gene amplification sequencing on them
and matched our data with an online comprehensive database.
We were happy to see that,
although our three strains had been previously identified bacteria,
two of them were not previously associated
with phthalate degradation, so this was actually a novel discovery.
JY: To better understand how this biodegradation works,
we wanted to verify the catabolic pathways of our three strains.
To do this, we extracted enzymes from our bacteria
and reacted with an intermediate of phthalic acid.
MW: We monitored this experiment with spectrophotometry
and obtained this beautiful graph.
This graph shows that our bacteria really do have
a genetic pathway to biodegrade phthalates.
Our bacteria can transform phthalates, which is a harmful toxin,
into end products such as carbon dioxide, water
I know some of you in the crowd are thinking,
well, carbon dioxide is horrible, it's a greenhouse gas.
But if our bacteria did not evolve to break down phthalates,
they would have used some other kind of carbon source,
and aerobic respiration would have led it
to have end products such as carbon dioxide anyway.
We were also interested to see that,
although we've obtained greater diversity
of bacteria biodegraders from the bird habitat site,
we obtained the most efficient degraders from the landfill site.
So this fully shows that nature evolves
through natural selection.
JY: So Miranda and I shared this research
at the Sanofi BioGENEius Challenge competition and were recognized
with the greatest commercialization potential.
Although we're not the first ones to find bacteria
that can break down phthalates,
we were the first ones to look into our local river
and find a possible solution to a local problem.
We have not only shown that bacteria
can be the solution to plastic pollution, but also that
being open to uncertain outcomes and taking risks
create opportunities for unexpected discoveries.
Throughout this journey, we have also discovered our passion for science,
and are currently continuing research
on other fossil fuel chemicals in university.
We hope that in the near future,
we'll be able to create model organisms
that can break down not only phthalates
but a wide variety of different contaminants.
We can apply this to wastewater treatment plants
to clean up our rivers
and other natural resources.
And perhaps one day we'll be able to tackle
the problem of solid plastic waste.
MW: I think our journey has truly transformed
our view of microorganisms,
and Jeanny and I have shown that
even mistakes can lead to discoveries.
Einstein once said,
"You can't solve problems by using the same kind
of thinking you used when you created them."
If we're making plastic synthetically, then we think
the solution would be to break them down biochemically.
Thank you. JY: Thank you.
Miranda Wang and Jeanny Yao
- Science fair winners
Miranda Wang and Jeanny Yao have identified a new bacteria that breaks down nasty compounds called phthalates, common to flexible plastics and linked to health problems. And they’re still teenagers. Why you should listen
After a visit to a plastic-filled waste transfer station last year, students Miranda Wang and Jeanny Yao learned that much of the plastic in trash may not degrade for 5,000 years. Synthesized into plastics are phthalates, compounds that make shower curtain liners, food wraps and other products bendable but may also adversely impact human reproductive development and health. As plastics slowly break down, these phthalates would leach into the surrounding environment.
So, the two young scientists tackled the problem and ultimately discovered strains of bacteria that have the potential to naturally degrade phthalates. Their work earned a regional first place in British Columbia for the 2012 Sanofi BioGENEius Challenge Canada, as well as a special award for the most commercial potential at the contest’s finals.
The original video is available on TED.com