MIT researchers are genetically engineering yeast to break down stubborn plant fibers into sugars that it can then ferment. This is a step towards a potentially cost-effective single-organism process for manufacturing cellulosic biofuels. The source of the genetic material: anaerobic fungi from the digestive system of a horse on a hay-only diet. By teaming up with genetic-sequencing experts at MIT, the researchers have developed a novel analytical approach that will enable them to determine which enzymes in gut fungi are key players in plant digestion and how those enzymes are made and assembled — information that will help them replicate the fungi’s cellulose-destroying capabilities in yeast. Their approach could reveal new enzymes that are champion cellulose degraders but naturally occur only in unknown organisms that cannot be grown in a lab. One promising source of renewable fuels is biomass from agricultural residues, grasses, and other dedicated energy crops. Methods exist to c