Lean and mean biomass-degrading fungus reveals capabilities for improved biofuel production

For millennia, civilization has long relied on nature’s bounty for shelter and sustenance, with cheap and plentiful supplies of fossil fuels powering the economic engine of the industrial age, leading to the broad diversity of products synthesized from petroleum. With rising concern about dependence on imported oil for transportation, the 21st century is signaling a shift towards “white” or industrial biotechnology—harnessing the metabolic processes of microbes to address energy challenges.

The research team compared the 34-million-nucleotide genome of T. reesei with 13 previously characterized fungi and discovered something counterintuitive. Despite its reputation as an avid plant polysaccharide degrader, T. reesei, was found to have the smallest inventory of genes powering its robust degradation machinery.

“We were aware of T. reesei’s reputation as a producer of massive quantities of degrading enzymes, however we were surprised by how few enzyme types it produces, which suggested to us that its protein secretion system is exceptionally efficient,” said Diego Martinez, the study’s lead author and researcher supported by DOE JGI at LANL, and at the University of New Mexico. Subsequently, he and his colleagues turned their attention to the complexities of T. reesei’s secretory pathway components, which they had a hunch played an important role in the organism’s success.

“While little appears to have changed in the secretion machinery since divergence with a common ancestor with yeast,” said Martinez, “there are some intriguing differences in the way T. reesei processes some protein bonds important for cellulase production.”

In their comparative analysis of T. reesei with other fungi, the team observed clustering of carbohydrate-active enzyme genes, which suggested a specific biological role: polysaccharide degradation. “While plant tissues are not likely the main source of nutrients for T. reesei, upon detection of cellulose and hemicellulose it seems that the organization of these degrading genes may be the key to a rapid response,” said Martinez.