Characterization of two β-xylosidases from Bifidobacterium adolescentis and their contribution to the hydrolysis of prebiotic xylooligosaccharides

Abstract

Xylooligosaccharides have strong bifidogenic properties and are increasingly used as a prebiotic. Nonetheless, little is known about the degradation of these substrates by bifidobacteria. We characterized two recombinant β-xylosidases, XylB and XylC, with different substrate specificities from Bifidobacterium adolescentis. XylB is a novel β-xylosidase that belongs to the recently introduced glycoside hydrolase family 120. In contrast to most reported β-xylosidases, it shows only weak activity on xylobiose and prefers xylooligosaccharides with a degree of polymerization above two. The remaining xylobiose is efficiently hydrolyzed by the second B. adolescentis β-xylosidase, XylC, a glycoside hydrolase of family 43. Furthermore, XylB releases more xylose from arabinose-substituted xylooligosaccharides than XylC (30% and 20%, respectively). The different specificities of XylB, XylC, and the recently described reducing-end xylose-releasing exo-oligoxylanase RexA show how B. adolescentis can efficiently degrade prebiotic xylooligosaccharides.

The Ability of Bifidobacteria To Degrade Arabinoxylan Oligosaccharide Constituents and Derived Oligosaccharides Is Strain Dependent

“…Although the extracellular cleavage of arabinose substituents by cluster II and IV strains suggests the presence of extracellular ␣-arabinofuranosidases, no such enzymes have been characterized in B. longum until now (11,37). Similarly, in B. adolescentis ATCC 15703, only ␣-arabinofuranosidases have been characterized that are located intracellularly (38). This suggests that other genes must be responsible for the extracellular cleavage of arabinose by the strains tested.…”

“…This might be explained by the existence of ␣-arabinofuranosidases with different specificities. Indeed, several ␣-arabinofuranosidases have been character- ized that are specific for Araf residues from monosubstituted Xylp, Araf residues from both mono-and disubstituted Xylp, and Araf residues from doubly substituted Xylp residues at position C-(O)-3 (38,39,41,42). Also, the degree of substitution (not determined in the present study) may be an important factor in the degradation of AXOS (less degradation with increasing A/X) and hence explain preferences for certain AXOS molecules (5,43).…”

Multifunctional Properties of Glycoside Hydrolase Family 43 from Paenibacillus curdlanolyticus Strain B-6 Including Exo-β-xylosidase, Endo-xylanase, and α-L-Arabinofuranosidase Activities

“…In contrast to common β-xylosidases, exo-β-xylosidase of GH43B6 showed weak activity against xylobiose and preferably hydrolysed xylooligomers with a degree of polymerisation higher than four. However, the existence of GH43 with a broad xylooligosaccharide specificity toward X2-X6 has been reported (Lagaert et al 2011). The hydrolysis action of GH43B6 was further elucidated when low branching xylan from birchwood (Fig.…”

Arabinoxylan Oligosaccharide Hydrolysis by Family 43 and 51 Glycosidases from Lactobacillus brevis DSM 20054

“…The bifidogenic effect of dietary (A)XOS was thoroughly studied and confirmed (1,7). Furthermore, several bifidobacterial ␣-L-arabinofuranosidases (both AXHm and AXHd3) (3,6,(8)(9)(10), as well as ␤-D-xylosidases (11,12) required for complete (A)XOS degradation, have been identified and characterized, whereas all of the enzymes reported so far (both AXH and ␤-xylosidases) are members of glycoside hydrolase (GH) family 43 or 51 (13).…”