Goats, sheep, and other herbivores eat many types of plants, and in the animals' guts, fungi digest the plant material. Researchers characterized several fungi involved in this digestion process and identified a large number of enzymes that work synergistically to degrade the raw biomass.
Industry is exploring strategies to more effectively turn grasses, wood, and other types of biomass into fuel or chemicals. Because the matrix of complex molecules found in plant cell walls—lignin, cellulose, and hemicellulose—is difficult to break down using biological methods, costly pretreatments with heat or chemicals are necessary. The discovery of new, highly effective biomass-degrading enzymes in fungi could accelerate the development of a process to convert plant feedstocks into fermentable sugars without pretreatment, potentially leading to more efficient conversion of raw biomass to biofuels and biobased products.
Scientists have long known that anaerobic fungi living in the guts of herbivores play a significant role in helping those animals digest plants. However, culturing these fungi in the lab is difficult because they cannot survive in the presence of oxygen and must be grown in sealed containers. A research team led by Michelle O'Malley at the University of California, Santa Barbara, isolated three species of these fungi in feces from goats, horses, and sheep. The enzymes expressed by these fungi work together to break down crude, untreated plant biomass. The fungi adapt their enzymes to the different kinds of plant materials eaten by these animals so that wood, grass, or agricultural waste all can be efficiently digested. Each of the fungi studied was found to contribute in a characteristic way, tailoring their combined action to the particular type of biomass being digested. These findings could help in identifying distinctive enzymes from other anaerobic gut fungi, with potential applications for biomass processing and sustainable biofuel production.
Office of Biological and Environmental Research
Michelle A. O'Malley
Department of Chemical Engineering
University of California, Santa Barbara
This work was supported by the Office of Biological and Environmental Research (BER) within the U.S. Department of Energy's (DOE) Office of Science under Early Career Research Program award DE-SC0010352. A portion of this research was performed under the JGI-EMSL Collaborative Science Initiative and used resources at DOE's Joint Genome Institute (JGI) and Environmental Molecular Sciences Laboratory (EMSL), which are DOE Office of Science user facilities and sponsored by BER. Authors also acknowledge support from the U.S. Department of Agriculture (Award 2011-67017-20459) and Institute for Collaborative Biotechnologies through grant W911NF-09-0001.
K. Solomon, C. Haitjema, J. Henske, S. Gilmore, D. Borges-Rivera, A. Lipzen, H. Brewer, S. Purvine, A. Wright, M. Theodorou, I. Grigoriev, A. Regev, D. Thompson, and M. O'Malley. "Early-branching gut fungi possess a large, comprehensive array of biomass-degrading enzymes." Science 351 (6278), 1192-1195 (2016). [DOI: 10.1126/science.aad1431].