Massachusetts Institute of Technology (MIT) researchers believe bacteria may hold the answers to some of the planets biggest energy challenges.
The idea of exploiting microbial products is not new. Humans have long enlisted bacteria and yeast to make bread, wine and cheese, and more recently discovered antibiotics that help fight disease. Now, researchers in the growing field of metabolic engineering are trying to manipulate bacteria’s unique abilities to help generate energy and clean up Earth’s atmosphere.
MIT chemical engineer Kristala Jones Prather sees bacteria as diverse and complex "chemical factories" that can potentially build better biofuels as well as biodegradable plastics and textiles.
"We’re trying to ask what kinds of things should we be trying to make, and looking for potential routes in nature to make them," said Prather, an assistant professor of chemical engineering.
She and professor Gregory Stephanopoulos are trying to create bacteria that make biofuels and other compounds more efficiently, while another professor, Catherine Drennan, hopes bacteria can one day help soak up pollutants such as carbon monoxide and carbon dioxide from the Earth’s atmosphere.
Found in nearly every habitat on Earth, bacteria are chemical powerhouses. Some synthesize compounds useful to humans, such as biofuels, plastics and drugs, while others break down atmospheric pollutants. Most rely on carbon compounds as an energy source, but species differ widely in their exact metabolic processes.
Metabolic engineers are learning to take advantage of those processes. Prather is developing bacteria that can manufacture fuels such as butanol and pentanol from agricultural byproducts, and Stephanopoulos is trying to make better microbial producers of biofuels by improving their tolerance to the toxicity of the feedstocks they ferment and products they make.
Manufacturing plastics and textiles using bacteria can be far less energy-intensive than traditional industrial processes, because most industrial chemical reactions require high temperatures and pressures (which require a great deal of energy to create). Bacteria, on the other hand, normally thrive around 30 degrees Celsius and at atmospheric pressure.
Prather is also working on bacteria that transform glucose and other simple starting materials into compounds that can be used to make biodegradable plastics such as PHA (polyhydroxyalkanoate).
"Biology has a lot of diversity that’s untapped and undiscovered, but the flip side is that it’s hard to engineer in precise ways," says Prather. "Nature has evolved to do what it does, and to get it to do something different is a nontrivial task."
Drennan is also looking to bacteria, but with a different goal in mind. Instead of using bacteria to build things, she’s studying how they break things down–specifically, carbon dioxide, carbon monoxide and other atmospheric pollutants.
Her microbes, found in a range of habitats including freshwater hot springs, absorb carbon dioxide and/or carbon monoxide and use them to produce energy. Such microbes remove an estimated one billion tons of carbon monoxide from Earth and its lower atmosphere every year.
"These bacteria are responsible for removing a lot of CO and CO2 from the environment," says Drennan. "Can we use this chemistry to do the same thing?"
To answer that question, Drennan and her students are using X-ray crystallography to decipher the structures of the metal-protein enzymes involved in the reactions, which they believe will allow them to figure out how the enzymes work.
Source: Anne Trafton, MIT News Office
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