But cellulosic processes are complex and expensive, Cate said. The plant material must first be broken down into sugars through a process called saccharification. Enzymes called cellulases are added to convert cellulose to short-chain sugars, called cellodextrins, and these must be further broken down into glucose molecules by the enzyme beta-glucosidase. Only then can yeast work its magic and turn the glucose into alcohol.
Other fungi, however, can digest cellulose, though they don't produce alcohol. One of these, Neurospora crassa, a common fungus whose preferred diet is fire-damaged plants, has been studied in the laboratory for more than 100 years, Cate said.
Last year, Chaoguang Tian, a former UC Berkeley post-doctoral fellow in Professor Louise Glass's laboratory who now is at the Tianjin Institute of Industrial Biotechnology in China, and William T. Beeson, a graduate student in UC Berkeley's College of Chemistry, along with Cate and other UC Berkeley researchers, conducted a genome-wide analysis of Neurospora crassa to locate genes that are turned on when the fungus grows on cellulose.
The genome-wide systems analysis turned up a family of genes which produces proteins that transport sugars into the Neurospora cell to be used as fuel. The researchers suspected that some of these transporters would allow Neurospora to import cellodextrins in particular, the two-, three- and four-glucose molecules (cellobiose, cellotriose and cellotetraose, respectively). A search through the genomes of other fungi that grow on plants turned up similar genes in many of them, including the black truffle, which is symbiot
|Contact: Robert Sanders|
University of California - Berkeley