title: Comparative analysis of the ability of Clostridium clariflavum strains and Clostridium thermocellum to utilize hemicellulose and unpretreated plant material.
abstract: BACKGROUND
  Among themophilic consolidated bioprocessing (CBP) candidate organisms, environmental isolates of Clostridium clariflavum have demonstrated the ability to grow on xylan, and the genome of C. clariflavum DSM 19732 has revealed a number of mechanisms that foster solubilization of hemicellulose that are distinctive relative to the model cellulolytic thermophile Clostridium thermocellum.
  
  
  RESULTS
  Growth experiments on xylan, xylooligosaccharides, and xylose reveal that C. clariflavum strains are able to completely break down xylan to xylose and that the environmental strain C. clariflavum sp. 4-2a is able to grow on monomeric xylose. C. clariflavum strains were able to utilize a larger proportion of unpretreated switchgrass, and solubilize a higher proportion of glucan, xylan, and arabinan, with strain 4-2a reaching the highest extent of solubilization of these components (64.7 to 69.4%) compared to C. thermocellum (29.5 to 42.5%). In addition, glycome immunoanalyses of residual plant biomass reveal differences in the extent of degradation of easily accessible xylans, with C. clariflavum strains having increased solubilization of this fraction of xylans relative to C. thermocellum.
  
  
  CONCLUSIONS
  C. clariflavum strains exhibit higher activity than C. thermocellum in the breakdown of hemicellulose and are capable of degrading xylan to xylooligomers and xylose. This capability seems to also play a role in the higher levels of utilization of unpretreated plant material.
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH USA ; BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge, Oak Ridge, TN USA ; Department of Biology, Hofstra University, Hempstead, NY USA.
authors.forename: Javier A
authors.initials: JA
authors.lastname: Izquierdo
authors.affiliation: BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge, Oak Ridge, TN USA ; Complex Carbohydrate Research Center, University of Georgia, Athens, GA USA.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Pattathil
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH USA ; BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge, Oak Ridge, TN USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Guseva
authors.affiliation: BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge, Oak Ridge, TN USA ; Complex Carbohydrate Research Center, University of Georgia, Athens, GA USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hahn
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH USA ; BioEnergy Science Center Oak Ridge National Laboratory Oak Ridge, Oak Ridge, TN USA.
authors.forename: Lee R
authors.initials: LR
authors.lastname: Lynd
keywords: CBP; Clostridium clariflavum; Clostridium thermocellum; Hemicellulose; Switchgrass