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Applied and Environmental Microbiology, February 2006, p. 1496-1506, Vol. 72, No. 2
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.2.1496-1506.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Paenibacillus sp. Strain JDR-2 and XynA₁: a Novel System for Methylglucuronoxylan Utilization

Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611

Received 22 September 2005/ Accepted 1 December 2005

Environmental and economic factors predicate the need for efficient processing of renewable sources of fuels and chemicals. To fulfill this need, microbial biocatalysts must be developed to efficiently process the hemicellulose fraction of lignocellulosic biomass for fermentation of pentoses. The predominance of methylglucuronoxylan (MeGAX_n), a ß-1,4 xylan in which 10% to 20% of the xylose residues are substituted with -1,2-4-O-methylglucuronate residues, in hemicellulose fractions of hardwood and crop residues has made this a target for processing and fermentation. A Paenibacillus sp. (strain JDR-2) has been isolated and characterized for its ability to efficiently utilize MeGAX_n. A modular xylanase (XynA₁) of glycosyl hydrolase family 10 (GH 10) was identified through DNA sequence analysis that consists of a triplicate family 22 carbohydrate binding module followed by a GH 10 catalytic domain followed by a single family 9 carbohydrate binding module and concluding with C-terminal triplicate surface layer homology (SLH) domains. Immunodetection of the catalytic domain of XynA₁ (XynA₁ CD) indicates that the enzyme is associated with the cell wall fraction, supporting an anchoring role for the SLH modules. With MeGAX_n as substrate, XynA₁ CD generated xylobiose and aldotetrauronate (MeGAX₃) as predominant products. The inability to detect depolymerization products in medium during exponential growth of Paenibacillus sp. strain JDR-2 on MeGAX_n, as well as decreased growth rate and yield with XynA₁ CD-generated xylooligosaccharides and aldouronates as substrates, indicates that XynA₁ catalyzes a depolymerization process coupled to product assimilation. This depolymerization/assimilation system may be utilized for development of biocatalysts to efficiently convert MeGAX_n to alternative fuels and biobased products.

This article has been cited by other articles:

• Chow, V., Nong, G., Preston, J. F. (2007). Structure, Function, and Regulation of the Aldouronate Utilization Gene Cluster from Paenibacillus sp. Strain JDR-2. J. Bacteriol. 189: 8863-8870 [Abstract] [Full Text]  
• St. John, F. J., Rice, J. D., Preston, J. F. (2006). Characterization of XynC from Bacillus subtilis subsp. subtilis Strain 168 and Analysis of Its Role in Depolymerization of Glucuronoxylan. J. Bacteriol. 188: 8617-8626 [Abstract] [Full Text]