Compost Microbes Adapted to Produce Switchgrass-Degrading Enzymes

The Science

Development of cellulosic biofuels from non-food crops is currently an area of intense research interest. Tailoring depolymerizing enzymes to particular feedstocks and pretreatment conditions is one promising avenue of research in this area. By incubating switchgrass with a mix of microbes isolated from compost, Joint BioEnergy Institute researchers provided the selective pressure needed to grow a new microbial community enriched with enzymes that degrade cell-wall polymers specific to switchgrass. The sample was incubated in a bioreactor for 31 days under typical composting conditions. Metagenomic sequencing of the switchgrass-adapted compost (SAC) community on day 31 was carried out to investigate the sample’s diverse pool of glycoside hydrolases-enzymes that break bonds between carbohydrate molecules. The sample contained a high proportion of genes encoding enzymes that attack the branches and backbone of a major hemicellulose in grass cell walls. Analysis of the small-subunit ribosomal RNA (rRNA) isolated from the microbial community revealed dramatic changes in the community profile with more than a 20-fold increase for some bacterial populations in the SAC. Although metagenomic DNA sequence is highly fragmented, making isolation of full genes from complex communities difficult, two full-length genes for cellulose-degrading enzymes were discovered, synthesized, expressed in Escherichia coli, and tested for enzyme activity.


Allgaier, M., A. Reddy, J. I. Park, N. Ivanova, P. D’haeseleer, S. Lowry, R. Sapra, T. C. Hazen, B. A. Simmons, J. S. VanderGheynst, and P. Hugenholtz. 2010. “Targeted Discovery of Glycoside Hydrolases from a Switchgrass-Adapted Compost Community,” PLoS One 5(1), e8812. DOI:10.1371/journal.pone.0008812.