Arabinofuranosidases are important accessory enzymes involved in the degradation of arabinose-containing poly- and oligosaccharides. Two arabinofuranosidases from the recently described novel anaerobic cellulolytic bacterium , designated Araf51 and Araf43, were heterologously expressed in and biochemically characterized. Araf51 not only removed arabinose moieties at O-3, O-2 and terminal O-5 positions of arabinose-containing oligosaccharides, but also exhibited exo-β-xylosidase side activity. In comparison, Araf43 preferably cleaved 1,3-linkages from arabinosyl disubstitutions. Araf51 and Araf43 demonstrated maximum activity at 70 °C and 57 °C, respectively. Judging from the genetic context and substrate specificity, Araf51 may decompose internalized arabino/xylo-oligosaccharides. The embedding of the Araf43 gene between genes for several putative xylanolytic enzymes, along with its enzymatic properties suggests that Araf43 cleaves arabinose decorations from heteroxylans extracellularly. The enzymes revealed completely converse activity profiles towards arabinan/arabinoxylan: Araf51 displayed strong activity on arabinan, while Araf43 prefers arabinoxylan. Araf51 dramatically stimulated the saccharification level of wheat arabinoxylan (WAX-RS) and sugar beet arabinan when administered along with xylanase M_Xyn10 or arabinanase Abn43, respectively. For WAX-RS degradation, the yield of arabinose and xylose was boosted 13.77-fold and 4.96-fold, respectively. The bifunctional activity, thermostability and high catalytic efficiency make Araf51 an interesting candidate for industrial applications.