At the 245th National Meeting and Exposition of the American Chemical Society in New Orleans, one of the high-lighted topics was getting at cellulose which is sealed away inside a tough network within the cell walls of plants to produce biofuels.
From horse manure to biofuel
Researchers are delving deeply into a treasure-trove of enzymes in fungi thriving in horse manure and the intestinal tracts of horses to produce biofuels for the future.
In this context, scientists described the discovery of a potential treasure-trove of candidate enzymes in fungi thriving in the feces and intestinal tracts of horses.
According to Michelle A. O'Malley, Ph.D, "Nature has made it very difficult and expensive to access the cellulose in plants. Additionally, we need to find the best enzyme mixture to convert that cellulose into sugar. We have discovered a fungus from the digestive tract of a horse that addresses both issues -- it thrives on lignin-rich plants and converts these materials into sugars for the animal. It is a potential treasure trove of enzymes for solving this problem and reducing the cost of biofuels."
The digestive tracts of large herbivores like cows and horses, which can digest lignin-rich grasses, have been a well-trodden path for scientists seeking such enzymes. But in the past, their focus has been mainly on enzymes in bacteria, rather than fungi, which include yeasts and molds.
The goal: Take the genes that produce such enzymes from gut fungi and genetically engineer them into yeasts. Yeasts already are used in time-tested processes on an industrial scale to produce huge quantities of antibiotics, foods and other products. That proven production technology would mean clear sailing for commercial production of biofuels.
O'Malley explained that several genes from gut fungi are unique compared to bacteria, since the fungi grow invasively into plant material. Also, they secrete powerful enzyme complexes that work together to break down cellulose. Until now, however, fungi have largely been ignored in the search for new biofuel enzymes -- and for good reason.
"There was relatively little scientific knowledge about fungi in the digestive tracts of these large animals," O'Malley explained. "They are there, but in very low numbers, making it difficult to study. The low concentrations also fostered a misconception that fungi must be unimportant in digestion of cellulose. And it is extremely difficult to isolate and grow these fungi to study their enzymes."
O'Malley's research group at the University of California, Santa Barbara, collaborated with researchers at the Broad Institute of the Massachusetts Institute of Technology and Harvard University. They worked with a gut fungus isolated from horse feces and identified all the genetic material that the fungus uses to manufacture enzymes and other proteins.
This collection of protein-encoding material -- the fungus's so-called "transcriptome" -- led to the identification of literally hundreds of enzymes capable of breaking through that tough lignin in plant cell walls and the cellulose within.
The team now is shifting through that bounty to identify the most active enzyme and working on methods for transferring the genetic machinery for its production into the yeast currently used in industrial processes.
The scientists acknowledged support from the United States Department of Agriculture, The Institute for Collaborative Biotechnologies through contract no. W911NF-09-D-0001 from the U.S. Army Research Office and the University of California, Santa Barbara.