Two extracellular α-arabinofuranosidases are required for cereal-derived arabinoxylan metabolism by Bifidobacterium longum subsp. longum

ABSTRACT

Members of the genus Bifidobacterium are commonly found in the human gut and are known to utilize complex carbohydrates that are indigestible by the human host. Members of the Bifidobacterium longum subsp. longum taxon can metabolize various plant-derived carbohydrates common to the human diet. To metabolize such polysaccharides, which include arabinoxylan, bifidobacteria need to encode appropriate carbohydrate-active enzymes in their genome. In the current study, we describe two GH43 family enzymes, denoted here as AxuA and AxuB, which are encoded by B. longum subsp. longum NCIMB 8809 and are shown to be required for cereal-derived arabinoxylan metabolism by this strain. Based on the observed hydrolytic activity of AxuA and AxuB, assessed by employing various synthetic and natural substrates, and based on in silico analyses, it is proposed that both AxuA and AxuB represent extracellular α-L-arabinofuranosidases with distinct substrate preferences. The variable presence of the axuA and axuB genes and other genes previously described to be involved in the metabolism of arabinose-containing glycans can in the majority cases explain the (in)ability of individual B. longum subsp. longum strains to grow on cereal-derived arabinoxylans and arabinan.

KEYWORDS:

• Dietary fiber
• prebiotic
• bifidobacterial
• probiotic
• gut microbiota

Acknowledgments

We would like to acknowledge the PrecisionBiotics Group Ltd., part of the Novonesis group for their support of this work. We thank the AlphaFold team for developing an excellent model and open source the software.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The sequencing data that support the findings of this study are openly available in NCBI at https://www.ncbi.nlm.nih.gov/ within the BioProject PRJNA1073879 and PRJNA1082215.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/19490976.2024.2353229.

Additional information

Funding

The work was supported by the Science Foundation Ireland (SFI) under grant No. 12/RC/2273 and 16/SP/3827.