The future is microscopic

 more than six billion tonnes of plastic waste end up in the ocean
Fall 2017
David Levin of the University of Manitoba is using bacteria to create renewable bioresins for making green biodegradable biocomposite materials for the transportation­ and aerospace industries.

 Westward Industries

New biocomposite materials for the GO-4, made by Winnipeg’s Westward Industries, will make this light and nimble utility vehicle even more efficient. Photo credit: Westward Industries

Watch any New York City cop drama, from Law & Order to Blue Bloods, and you will see what filmmakers call an “establishing” shot. It usually depicts a brick or sandstone police station where much of the action takes place, along with several iconic police cars. But look closer and you may see another type of police vehicle: a 130 centimetre-wide, three-wheeled unit called the GO-4. Used for street ticketing, meter reading or patrolling crowded spaces, this unassuming machine is on the front lines in a new effort to replace oil-derived plastics with something cleaner, greener and more sustainable.

David Levin

David Levin of the University of Manitoba

The GO-4 is manufactured by Westward Industries, a family-owned company based in Winnipeg. Westward is one of the primary collaborators with Winnipeg’s Composites Innovation Centre (CIC), a not-for-profit corporation dedicated to researching and developing innovative composite materials. CIC, in turn, oversees the Prairie Agricultural Fibre Characterization Industrial Technology (FibreCITY) initiative, which focuses on the manufacturing of products, including parts for vehicles like the GO-4, out of natural materials such as flax and hemp. A key CIC collaborator is David Levin, a molecular biologist and biotechnologist in the University of Manitoba’s Department of Biosystems Engineering whose lab group is a multi-disciplinary mix of students, scientists and engineers with expertise in microbiology, biochemistry, genome sciences and bioprocess engineering. 

Levin’s team aims to redesign parts of the GO-4 and is working closely with the CIC, which is developing the vehicle’s composite material parts from natural fibre composites (NFCs) to improve both performance and sustainability. The project, dubbed Fibre Composite and Biomatrix Genomics (FiCoGEN), is also supported by Genome Canada and Genome Prairie under its Genomic Applications Partnership Program (GAPP).  NFCs will allow the GO-4’s cab structure to be moulded into the appropriate shapes. They are light, resulting in improved mileage for the already-efficient vehicle. Levin says that this factor alone bodes well for the replacement of petroleum-based fibreglass with NFCs, not only for cars and trucks but the aerospace industry, where mass must always be kept to a minimum. Biocomposites also have the advantage of being renewable and potentially more biodegradable than composites in use today. 

The team is also developing biocomposites for other sectors, specifically medicine. In collaboration with U of M’s Song Liu, who is also in biosystems engineering, the team uses electrospinning of poly-3-hydroxyalkanoate (PHA) polymers — using an electrical charge to draw the cellulose into very thin fibres — to make a biodegradable and biocompatible nano-fibre structure material for biomedical applications such as wound dressings.

But swapping out fibreglass for biocomposites is not a straightforward process. Levin and his collaborators need to make sure that the properties of their materials meet or exceed those in use today. And since the bottom line is always of primary concern for industry, they must also ensure that biocomposite parts can be made at or below the cost of conventional materials. 

However, a challenge with the development of NFCs is the reluctance of polyvinyl resin to bind with them the way they do with petroleum-based glass fibres. This leads to performance issues; while the properties of the biocomposite are comparable to fibreglass, they aren’t quite the same. “Everyone wants these green, biocomposite materials but no one has gotten to the point of where we have materials as good or better than fibreglass,” says Levin. “So that’s the driving force of the FiCoGEN project.”

There is also the fact that polyvinyl resin is still petroleum-based, not renewable like the plant-based fibres it is binding together. To make a fully green biocomposite material, Levin and his collaborators need to make a bio-based plastic that can compete with polyvinyl resin. And to do that, they are turning to the tiniest members of their team.

Microscopic FiCoGEN team members

Finding a replacement for polyvinyl resin led Levin and his team to a PHA. Produced by soil bacteria such as Cupriavidus necator (previously known as Ralstonia eutropha) and a number of species in the genus Pseudomonas, PHAs are biopolymers synthesized by bacteria to store energy, similar to the role of fat in our own metabolism. When their nutrient source starts to become depleted, the bacteria ferment sugar and lipids into PHAs, saving precious sustenance for hard times ahead. When they are starved completely, the bugs can then break down the PHA polymers, using them as an energy source.

As polymers with either thermoplastic or elastomeric properties, PHAs have the potential to replace synthetic substances like polyvinyl resins. The major challenge is scale: in order to obtain enough polymer to glue together natural fibres, you have to grow what Levin calls “a whole lot of bacteria.” Using industrial fermentation reactors, the team has managed to produce about one kilogram of polymer from 1,500 litres of bacterial culture. This is not nearly enough for industrial purposes but it is enough to test the material on a lab scale. Levin, his team and Ning Yan at the University of Toronto’s Faculty of Forestry are experimenting with different formulations of flax fibres and biopolymers to find out which ones have the best tensile strength, elasticity and thermal stability. The goal is to get something as good as — or better than — conventional fibreglass.

In the meantime, the team is also thinking about scale-up. By altering the balance of nutrients on which the bacteria grow, the team has been able to trick the bugs into storing extremely high amounts of PHAs. Some cultures result in a cell mass that is anywhere from 60 to 80 percent polymer. In this case, the polymer doesn’t have to be extracted from the cell: researchers can simply use the entire bacterium when making a resin.

This past August, the lab was all hands on deck as Levin and his researchers worked on producing as much of the polymer as they could in order to undergo testing and assessment. But whether or not the process will be economically viable at the industrial scale remains to be seen and depends on factors that are well beyond the control of researchers. 

Some of the globe’s more than six billion tonnes of plastic waste end up in the ocean, devastating­ marine life. Helping find solutions to this environmental threat is David Levin, who studies­ bacteria that degrade such polymers as polyethylene, used to make plastic bags.

Some of the globe’s more than six billion tonnes of plastic waste end up in the ocean, devastating­ marine life. Helping find solutions to this environmental threat is David Levin, who studies­ bacteria that degrade such polymers as polyethylene, used to make plastic bags.

Oil prices influence research­ 

During the peak of the Great Recession, the price of West Texas Intermediate crude oil, regarded as a world reference price, rose to  $147.90 per barrel, according to the provincial government’s Alberta Economic Dashboard. Under these conditions, alternate sources of fuel begin to look economically attractive and many researchers secured funding to investigate the conversion of waste materials like straw, hemp hurds, flax shives and wood chips into biofuels. 

Levin was among them. In 2009 he, along with U of M microbiologist Richard Sparling, received $10.4 million for an international collaboration based on converting agricultural waste into biofuels such as ethanol and hydrogen. At the time, much of this waste material was simply burned and the smoke was causing distress for Winnipeggers near agricultural areas. The main focus of the research was studying the genomes of bacteria in the hopes of finding enzymes that could break down the natural polymers cellulose and lignin into simple sugars, which could then be fermented into fuels. 

Then oil prices fell. This past July, a barrel of West Texas Intermediate averaged just $46.68. Combined with explosive growth in the natural gas fracking industry, the economic viability of certain biofuels has begun to look more dubious. For example, Levin says, at one point dried distiller grain — a high-nutrient animal feed for cows and pigs that is a byproduct of ethanol production — was more valuable than the ethanol itself. (Most of Canada mandates that fuel for vehicles must contain 10 percent ethanol, however, this is government subsidized.) 
Under these conditions, switching his focus from biofuels to bioproducts seemed like a prudent move. Some of Levin’s first research in the area was on bacterial-derived molecules called 3-hydroxy fatty acids. By varying the number of carbons in the subunit side chains, Levin and his team could control the physical and thermal properties of the resulting polymers, including thermal stabilities, melting points and crystallinities. 

Lately however, Levin has begun to think beyond agricultural products. He believes that the power of bacteria to accomplish complex chemical transformations could also help deal with another environmental challenge: the proliferation of petroleum-based plastic.

Bugs that devour plastic

Earlier this year, a team of US researchers published an article in Science Advances that estimated the global production, use and fate of plastic since the Second World War. They estimated that of the more than 8.3 percent billion tonnes of plastics created, only nine has been recycled, with a further 12 percent incinerated. This leaves more than 6.3 billion tonnes of plastic waste sent to landfill, some of which eventually finds its way into the world’s oceans. Over time, sunshine and weathering break it into pieces too small to see. These microscopic particles, says Levin, are far from harmless.

That’s because filter feeders, from phytoplankton to clams, oysters and shrimp, wash water through specialized organs in order to gather organic matter. These filters can become clogged with nano-sized particles of plastic. Fish and other organisms eat these creatures, which harms their digestion. “Their guts get full of plastic and can’t be degraded and it’s a major catastrophe in the making,” says Levin, who considers the accumulation of plastic in the environment as significant an environmental problem as climate change.

But despite the fact that these plastics were synthetically created, there may be some bacteria capable of degrading them. The Levin lab is studying three common soil bacteria that actively utilize a wide range of carbon-based molecules for growth and metabolism and could potentially survive on polymers such as polyethylene, best known for its use in plastic bags. These include the aforementioned Cupriavidus necator as well as Actinobacter pittii and Pseudomonas putida, all three of which can also synthesize PHAs.

“If we have organisms that can eat polyethylene and turn it into biomass, you’re basically recycling it,” says Levin. He draws a parallel to anaerobic digesters, which leverage bacterial communities to turn organic waste from farms or cities into fuel. Piggy-backing on the FiCoGEN project, Levin is looking to create bacterial cultures that overproduce the enzymes required to break down and digest polyethylene, potentially turning it into renewable polymers like PHAs. If successful, he hopes to apply for further funding to grow these cultures on industrial scales.

Whether he is developing biofuels or bioproducts, transforming cellulose into composite materials or studying bacteria that could recycle plastic bags, Levin remains fascinated by the potential of Mother Nature herself to provide solutions for many of the planet’s pollution problems. “My research career has been a journey to understand the processes of nature and use these to develop technologies that may be able to restore harmony between humans and nature,” he says.