BACKGROUNDBacillus subtilis 168 secretes endoxylanases Xyn11A and Xyn30C and arabinofuranohydrolase Axh43 that process xylans in hemicellulose fractions. Engineered strain MR44 with a deletion in the xynA gene encoding Xyn11A, converts hardwood methylglucuronoxylans (MeGX(n)) of dicots to defined acidic xylooligosaccharides (U-XOS) with a single methylglucuronate linked to xylooligosaccharides with an average ratio of one methylglucuronate to 6-7 xyloses as value-added products. The MR44 strain also secretes Axh43 that catalyses release of arabinose from methylglucuronoarabinoxylans (MeGAX(n)) of monocots. RESULTSMR44 strain efficiently processes sorghum MeGAX(n) with 493 mg g(-1) yields of purified U-XOS. H-1-NMR analysis of U-XOS purified by anion exchange chromatography structurally defined the U-XOS with an average degree of polymerization of xylose units (DP) of 11-12 and a single 4-O-methyl-glucuronic acid -1,2-linked on average to one of 11-12 xylose residues each penultimate to the reducing terminal xylose. CONCLUSIONThis study demonstrates the ability of Bacillus subtilis strains to process MeGAX(n) for production of U-XOS from monocots, including energy crops and agricultural residues. The U-XOS with an average DP of 11-12 from sweet sorghum MeGAX(n) compared with 6-7 from sweetgum MeGX(n) extends their applications as biologicals and for production of pentosan polysulfates with applications in human and veterinary medicine. (c) 2015 Society of Chemical Industry