DOE's Joint Genome Institute (JGI) achieved a key milestone to understanding fermentative organisms by sequencing the genome for the fungus Pichia stipitis. The fungus is proficient at fermenting xylose, one of the main sugars in cellulosic biomass. The research performed in collaboration with the U.S. Forest Service's Forest Product Laboratory (FPL) identified numerous genes in the fungus that allow it to break down cellulose and ferment the xylose. The researchers also analyzed the metabolic pathways associated with those genes.
P. stipitis is the most proficient microbial fermenter in nature of the five-carbon "wood sugar" xylose--abundant in hardwoods and agricultural leftovers, which represent a motherlode of bioenergy fodder.
"The information embedded in the genome sequence of Pichia has helped us identify several gene targets to improve xylose metabolism," said Thomas W. Jeffries of the Forest Products Laboratory in Madison, Wisconsin. "We are now engineering these genes to increase ethanol production." Jeffries said that yeast strains like Pichia have evolved to cope with the oxygen-limited environment rich in partially digested wood that is encountered in the gut of insects, from where the sequenced strain was originally isolated.
FPL has a Cooperative Research and Development Agreement (CRADA) in place with a New York City-based bioenergy company, Xethanol Corporation, which plans to integrate Dr. Jeffries' findings into its large-scale biofuels production processes.