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

ABSTRACT

Metabolism of non-digestible dietary glycans directly influences the structure and composition of human gut microbiota and, in turn, the host health. ß-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 ß-manno-oligosaccharides from guar gum, locust bean gum, konjac root, and copra meal generated using GH26 endo-ß-mannanase (ManB-1601). Further, to gain insights into the underlying molecular mechanism, a whole-genome microarray analysis, RT-qPCR, and molecular docking studies were employed to reconstruct the copra meal ß-manno-oligosaccharides (CM-ß-MOS) utilisation pathway in B. adolescentis DSMZ 20083. B. adolescentis DSMZ 20083 grew appreciably (O.D600 nm up to 0.8) on all tested ß-manno-oligosaccharides but maximally on CM-ß-MOS. CM-ß-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-ß-MOS, respectively, while GH1 ß-glucosidase, and GH32 ß-fructofuranosidase possibly cleave linear CM-ß-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 up-regulated following the growth on CM-ß-MOS. This is the first study reporting on possible molecular determinants used by B. adolescentis DSMZ 20083 to utilise ß-manno-oligosaccharides. Our studies can prove resourceful to food and nutraceutical industries, aiming at precision microbiome modulation using ß-manno-oligosaccharides.