To overcome the challenge of breaking down cellulosic biomass for commercial biofuel production, which involves the application of high temperatures, a team of researchers including DOE JGI’s Martin Allgaier, now at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Germany, and Phil Hugenholtz, now director of the Australian Centre for Ecogenomics at the University of Queensland in Australia, focused on microbial communities in a composting bioreactor that are used to extreme conditions.
Bioenergy candidate feedstock switchgrass in Nebraska. (Image by Stephen Ausmus, USDA-ARS)
“The goals of this study were to select microbial communities and secreted enzymes that decompose bioenergy feedstocks in a thermophilic high-solids environment, and to examine the evolution of microbial community structure and enzyme activity during enrichment,” the team wrote in the September issue of Biotechnology and Bioengineering.
Using corn stover and switchgrass as sample feedstocks for the bioreactor operating at 55°C (131°F), they measured the levels of activity demonstrated by the microbes and identified the most active enzymes in each case.
The researchers found that the composition of the microbial communities in the bioreactor adapted to the feedstock provided, and that in the case of the switchgrass-fed bioreactor, the most active enzyme was xylanase.
“Such differences in the enriched community and enzyme activities demonstrate the need for specialized metabolic pathways and activities that depend on the unique plant cell wall polysaccharide composition of biofuel feedstocks,” the team concluded.