By Sydney Heimer
A UW-Madison group hopes to transform the plastics industry by developing a plant-based plastic.
What started in the 1970s as a hunt for a “critter” that could clean areas contaminated by hydrocarbons has turned into a research project that could forever change the plastics industry. UW-Madison’s Great Lakes Bioenergy Research Center (GLBRC), funded by the Department of Energy, has taken a great interest in this “critter” — the microbe Novosphingobium aromaticivorans.
Daniel Noguera, a UW-Madison professor in the department of civil and environmental engineering, along with graduate student Miguel Perez are the resident “critter” experts of GLBRC. Their original goal was to convert lignin, a renewable resource found in the cell walls of woody plants, into marketable products. “Lignin right now is not a product that has a lot of use,” says Noguera, “Our goal is to make lignocellulosic (plant-based) biomass a source of fuels and chemicals as substitutes for petroleum-based products like plastic.”
Apart from petroleum, lignin is the largest source of aromatic compounds — compounds that are the building blocks for a wide array of materials, including many plastics. The problem is that these aromatic compounds in woody biomass are notoriously difficult to access, and chemical methods to extract them result in mixtures that are difficult to purify. That’s where N. aromaticivorans comes in. This soil bacteria grows exceptionally well when using aromatic compounds as their food source.
“We were looking for a microbe that was able to eat as many aromatics as possible and fast,” says Perez. Though there are other microbes out there that can digest aromatic compounds, N. aromaticivorans is special in that it can transform a wide range of compounds into a few intermediate molecules. It also seems to eat all aromatic compounds at the same time. “That is something unique and very useful. This one is the best,” says Perez. The group is using these properties of N. aromaticivorans to engineer pathways that turn the intermediate molecules into useful products. Perhaps the most attractive of these products is a pyrone-dicarboxylic acid (PDC), a naturally occurring molecule that can be polymerized to produce plastics from a renewable resource.
“We have a goal of demonstrating we can go from a tree to a product in an economically feasible way.” — Daniel Noguera.
“This compound could be very interesting for industrial applications,” says Noguera. Apart from being a precursor for plastic that can be biodegradable, PDC-based plastics will not leech harmful chemicals into the environment like petroleum-based plastics. “PDC is a natural intermediate in metabolic pathways present in many microbes out there… if this compound leeches into the environment, we expect it to be eaten by another microbe,” says Perez. In addition, finding a replacement for petroleum-based chemicals contributes to reducing our dependence on fossil fuels, thus decreasing the associated environmental effects, including greenhouse gas emissions and oil spills.
In the next step of their research, Noguera and Perez hope to improve the yield of PDC from the plant-derived aromatic compounds and scale up the process to demonstrate industrial relevance. In addition, they hope to diversify the compounds that N. aromaticivorans can produce from lignin, so this discovery can have an even wider range of possible applications. “PDC is one compound, but the idea is we can use one microbial chassis as the tool to make as many industrially relevant compounds as we can, from lignin — a renewable resource,” says Perez.
Noguera, Perez, and their group recently published their work in the journal Green Chemistry. Their article was later highlighted by the Department of Energy as an example of successful DOE-funded research. In just a few years, their work could completely transform the plastics industry by creating a sustainable alternative to the petroleum-based plastics currently in use. “We have a goal of demonstrating we can go from a tree to a product in an economically feasible way,” says Noguera. “And we’re not too far away” Perez adds.