Xylanases play a central role in lignocellulose deconstruction and hold broad biotechnological potential. To investigate the functional basis for the coexistence of multiple xylanases in Cellulomonas sp. B6, we characterized five extracellular enzymes (CsXyns), four GH10 and one GH11, coinduced during growth on plant biomass. Each CsXyn-encoding gene resides in a distinct genomic region, and the recombinant xylanases display diverse biochemical properties, with CBMs contributing to their stability. Product profiling (HPAEC-PAD, MALDI-TOF MS, NMR, methylation analysis) revealed that CsXyns generate distinct mixtures of linear and substituted arabino- and glucurono-xylooligosaccharides (AXOS and UXOS), highlighting intrafamily variability in substrate recognition. Molecular modeling suggested subtle active-site differences among GH10 CsXyns underlying these patterns. Moreover, AXOS present in wheat bran hydrolysates produced by individual CsXyns were metabolized by probiotic strains with apparent enzyme-dependent selectivity. These findings reveal the functional diversity of CsXyns and emphasize how subtle structural features shape oligosaccharide profiles and biological roles.
Ontañon et al. (Fri,) studied this question.