Monday, April 19, 2010
LL Conference Facility (Hilton Clearwater Beach)
Thermophilic microbial communities that are active in a high-solids environment offer great potential for the discovery of enzymes that decompose bioenergy feedstocks. In this study compost was used as an inoculum source to enrich thermophilic microbial communities and associated enzymes that hydrolyze cellulose and hemicellulose in solid-state fermentation. Feedstocks included switchgrass, corn stover, eucalyptus and rice straw. Decomposition of cellulose and hemicellulose by microorganisms is usually delayed by the presence of sugars; therefore ethanol and water extracted feedstocks were used for enrichment studies. To initiate the studies, extracted feedstocks were wet with minimal media, inoculated with finished green waste compost from a commercial facility, transferred to solid-state fermentation reactor arrays, and incubated under aerobic conditions at 55oC. The resulting enriched communities were transferred to fresh extracted material every two weeks. After each two-week incubation period, adapted communities reduced solids an average of 30% for switchgrass and 22% for corn stover. Respiration levels increased with successive enrichments. Overall, the changes for switchgrass were more pronounced than for corn stover; solids reduction between the first and second time points increased 4-fold for switchgrass while it remained relatively constant for corn stover. Also, enzyme activities significantly increased with each switchgrass enrichment, while activities remained relatively constant for corn stover. Final samples will be included in a coordinated metagenomics and enzyme discovery effort.