title: Discovery of microorganisms and enzymes involved in high-solids decomposition of rice straw using metagenomic analyses.
abstract: High-solids incubations were performed to enrich for microbial communities and enzymes that decompose rice straw under mesophilic (35°C) and thermophilic (55°C) conditions. Thermophilic enrichments yielded a community that was 7.5 times more metabolically active on rice straw than mesophilic enrichments. Extracted xylanase and endoglucanse activities were also 2.6 and 13.4 times greater, respectively, for thermophilic enrichments. Metagenome sequencing was performed on enriched communities to determine community composition and mine for genes encoding lignocellulolytic enzymes. Proteobacteria were found to dominate the mesophilic community while Actinobacteria were most abundant in the thermophilic community. Analysis of protein family representation in each metagenome indicated that cellobiohydrolases containing carbohydrate binding module 2 (CBM2) were significantly overrepresented in the thermophilic community. Micromonospora, a member of Actinobacteria, primarily housed these genes in the thermophilic community. In light of these findings, Micromonospora and other closely related Actinobacteria genera appear to be promising sources of thermophilic lignocellulolytic enzymes for rice straw deconstruction under high-solids conditions. Furthermore, these discoveries warrant future research to determine if exoglucanases with CBM2 represent thermostable enzymes tolerant to the process conditions expected to be encountered during industrial biofuel production.
authors.affiliation: Joint BioEnergy Institute, Emeryville, California, United States of America ; Biological and Agricultural Engineering, University of California Davis, Davis, California, United States of America.
authors.forename: Amitha P
authors.initials: AP
authors.lastname: Reddy
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Simmons
authors.forename: Patrik
authors.initials: P
authors.lastname: D'haeseleer
authors.forename: Jane
authors.initials: J
authors.lastname: Khudyakov
authors.forename: Helcio
authors.initials: H
authors.lastname: Burd
authors.forename: Masood
authors.initials: M
authors.lastname: Hadi
authors.forename: Blake A
authors.initials: BA
authors.lastname: Simmons
authors.forename: Steven W
authors.initials: SW
authors.lastname: Singer
authors.forename: Michael P
authors.initials: MP
authors.lastname: Thelen
authors.forename: Jean S
authors.initials: JS
authors.lastname: Vandergheynst
mesh_terms: D039903:Actinobacteria / Q000235:genetics / Q000378:metabolism; D002480:Cellulase / Q000235:genetics / Q000378:metabolism; D056186:Metagenomics / Q000379:methods*; D012275:Oryza; D020560:Proteobacteria / Q000235:genetics / Q000378:metabolism; D012988:Soil Microbiology; D014995:Xylosidases / Q000235:genetics / Q000378:metabolism
chemical_list: D014995:Xylosidases; D002480:Cellulase