What’s so great about ethanol? Chemical engineer Kristala Jones Prather thinks she can design a better biofuel — one that’s closer to the octane of gasoline and doesn’t absorb quite as much metal-corroding water.

The U.S. Department of Energy reports that the U.S. spends nearly $1 billion a day on imported oil. Fuels derived from biomass hold a great deal of promise as renewable energy sources and may significantly diversify the menu of transportation fuel options available to consumers. To produce a better biofuel, Prather, the Theodore T. Miller Career Development Associate Professor of Chemical Engineering, looks for molecules that have physical and chemical characteristics that — unlike ethanol — will make them compatible with today’s cars, pipelines, and other aspects of the U.S. petroleum infrastructure.

“We live in a world where liquid transportation fuels dominate. So given that reality, we’ve got to come up with alternatives that will work within the existing infrastructure,” she says. Butanol, or butyl alcohol, has been demonstrated to work in vehicles designed to run on gasoline and packs more of an octane punch than ethanol. Prather looks to this and other natural pathways for inspiration to design biosynthetic routes to new molecules.

Prather is enlisting the help of bacteria as micro biofuel factories. A bacterium called Clostridium acetobutylicum can ferment glucose to produce butanol, but it’s not very efficient. Prather has genetically tweaked other bacteria such as E. coli to use sugars in plant material to churn out butanol. In the process, Prather has happened upon new ideas about how to produce even better biofuels. The secret is in the enzymes that drive the fermentation process, so Prather has teamed up with Bruce Tidor, MIT professor of biological engineering and computer science, to engineer new enzymes and to predict which ones would be most effective in which biological systems. “Microbes are promising as chemical factories because of the ease with which these enzymes can be introduced into them from a wide variety of natural sources,” she says. Additionally, there is already a rich and growing body of industrial experience in using microbial systems to produce biofuels and biochemicals at very high volumes.

Prather, whose work is funded by Shell Global Solutions, sees biofuels as one of a diverse array of solutions to the energy crisis. “We can easily run into a situation where the rate at which we consume biomass is greater than the rate at which we can produce it,” she warns. But how long it takes to implement a solution is key, and “in the short term, biofuels can be more rapidly brought on line than other alternative energy sources, especially for transportation.