The majority of plant matter we have available to produce biofuels comes in the form of cellulose, a long polymer of sugars. It's easiest to convert this material to ethanol, but that creates its own problems: ethanol is less energy dense than petroleum-based fuels, and most vehicles on the road can't burn more than a 15 percent mix of ethanol and standard gasoline.
These disadvantages have led a number of labs to look into ways of using a cellulose feedstock to produce something more like standard fuels. In yesterday's Nature, researchers proposed a clever way of doing this: take the biochemical pathway that normally burns fat and run it in reverse.
Source: Need biofuel from bacteria? Run their fat-burning cycle in reverse