Waste products such as grass clippings and wood chips -- once thought too difficult to turn into ethanol -- may soon be fodder for hungry, gene-tweaked bacteria. The findings in the March 2 Proceedings of the National Academy of Sciences may empower scientists to engineer ethanol-producing super-organisms that can make clean-burning fuel from the nation's one billion unused tons of yearly biomass production.
"This is the first revelation of how a bacterium chooses from its more than 100 enzymes to break down a particular biomass," said David Wu, professor in the Department of Chemical Engineering at the University of Rochester. "Once we know how a bacterium targets a particular type of biomass, we should be able to boost that process to draw ethanol from biomass far more efficiently that we can today."
Ethanol holds the promise of a clean, renewable alternative to fossil fuels, but deriving it from plants is difficult. Producing it from corn is the easiest method, but doing so on a large scale would drive up the price of corn, corn starch, and even tangential foods like beef, since cows are fed on corn -- not to mention all the energy spent fertilizing, maintaining and harvesting a crop like corn. Conversely, deriving ethanol from plant materials such as the corn stalks and wood chips is challenging because the plants' cellulose is a very tough substance to break down, making for an inefficient process.
Wu's technique may prove much more effective than traditional methods. Instead of using separate steps to break down biomass into glucose and ferment the glucose into ethanol, as is currently done, Wu is working on a way to make a bacterium break down and ferment plant biomass efficiently in just one