The team, led by Mostafa Elshahed, associate professor of microbiology and molecular genetics described multiple unique features within the genome of the rumen fungus, organisms that reside in the gut of ruminant animals. The team found the fungus to be remarkably efficient at digesting plant biomass.

Unlike the absolute majority of fungi that are free-living and breathe atmospheric oxygen, rumen fungi have a restricted habitat in the rumen and alimentary tract of herbivores. They grow in the absence of oxygen, have adapted their genome to living in the presence of a large and diverse number of bacteria, and have even acquired useful genes from these bacteria, including multiple genes that aid in digestion of plant biomass.

The concurrent capability of plant biomass degradation, known as saccharification, and product formation from sugars, known as fermentation, renders anaerobic fungi very promising agents for consolidating various processes in a biofuel production scheme, an approach that significantly lowers the cost of biofuel production.

—Mostafa Elshahed

The team’s genomic and experimental analyses indicate the fungus efficiently degrades a wide range of non-crop plant materials, such as switchgrass, corn stover, sorghum and energy cane. The extent of plant biomass degradation has rarely been observed in other microorganisms.

Experimental analysis indicated that strain C1A is a remarkable biomass degrader, capable of simultaneous saccharification and fermentation of the cellulosic and hemicellulosic fractions in multiple untreated grasses and crop residues examined, with the process significantly enhanced by mild pretreatments. This capability, acquired during its separate evolutionary trajectory in the rumen, along with its resilience and invasiveness when compared to prokaryotic anaerobes, render anaerobic fungi promising agents for consolidated bioprocessing schemes in biofuels production.

—Youssef et al.

The next phase of the team’s work will be to improve the ratio of ethanol to acids produced by the degradation of plant biomass from this fungus. The fungus currently produces more acids than ethanol as a final product.

Resources

• Noha H. Youssef, MB Couger, Christopher G. Struchtemeyer, Audra S. Liggenstoffer, Rolf A. Prade, Fares Z. Najar, Hasan K. Atiyeh, Mark R. Wilkins, and Mostafa S. Elshahed (2013) Genome of the anaerobic fungus Orpinomyces sp. C1A reveals the unique evolutionary history of a remarkable plant biomass degrader. Appl. Environ. Microbiol. doi: 10.1128/AEM.00821-13