Insights into β-manno-oligosaccharide uptake and metabolism in Bifidobacterium adolescentis DSMZ 20083 from whole-genome microarray analysis

Metabolism of non-digestible dietary glycans directly influences the structure and composition of human gut
microbiota and, in turn, the host health. β-Mannans form an integral component of the modern diet as naturally
occurring dietary fibre or additives in processed foods. In the present study, in vitro fermentation and TLC studies
were used to determine the ability of adult-associated Bifidobacterium adolescentis DSMZ 20083 to utilise
β-manno-oligosaccharides from guar gum, locust bean gum, konjac root, and copra meal generated using GH26
endo-β-mannanase (ManB-1601). Further, to gain insights into the underlying molecular mechanism, a wholegenome
microarray analysis, RT-qPCR, and molecular docking studies were employed to reconstruct the copra
meal β-manno-oligosaccharides (CM-β-MOS) utilisation pathway in B. adolescentis DSMZ 20083. B. adolescentis
DSMZ 20083 grew appreciably (O.D600 nm up to 0.8) on all tested β-manno-oligosaccharides but maximally on
CM-β-MOS. CM-β-MOS having DP2–3 were found to deplete from the fermentation media. Whole-genome
transcriptome analysis, RT-qPCR, and molecular docking studies suggested that in B. adolescentis DSMZ
20083, ABC & MFS transporters are possibly involved in the uptake of DP ≥ 2 and DP ≥ 3 linear CM-β-MOS,
respectively, while GH1 β-glucosidase, and GH32 β-fructofuranosidase possibly cleave linear CM-β-MOS into
monosaccharides. Sugar absorption and utilisation pathways; Bifid shunt, ABC transport system, pyruvate
metabolism, glycolysis/gluconeogenesis, pentose, and glucouronate inter-conversions were also found upregulated
following the growth on CM-β-MOS. This is the first study reporting on possible molecular determinants
used by B. adolescentis DSMZ 20083 to utilise β-manno-oligosaccharides. Our studies can prove
resourceful to food and nutraceutical industries, aiming at precision microbiome modulation using β-mannooligosaccharides.