초록
<P><B>Background</B></P><P>Among themophilic consolidated bioprocessing (CBP) candidate organisms, environmental isolates of <I>Clostridium clariflavum</I> have demonstrated the ability to grow on xylan, and the genome of <I>C. clariflavum</I> DSM 19732 has revealed a number of mechanisms that foster solubilization of hemicellulose that are distinctive relative to the model cellulolytic thermophile <I>Clostridium thermocellum</I>.</P><P><B>Results</B></P><P>Growth experiments on xylan, xylooligosaccharides, and xylose reveal that <I>C. clariflavum</I> strains are able to completely break down xylan to xylose and that the environmental strain <I>C. clariflavum</I> sp. 4-2a is able to grow on monomeric xylose. <I>C. clariflavum</I> 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 <I>C. thermocellum</I> (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 <I>C. clariflavum</I> strains having increased solubilization of this fraction of xylans relative to <I>C. thermocellum</I>.</P><P><B>Conclusions</B></P><P><I>C. clariflavum</I> strains exhibit higher activity than <I>C. thermocellum</I> 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.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s13068-014-0136-4) contains supplementary material, which is available to authorized users.</P>