Structural Diversity and Prebiotic Potential of Short Chain β-manno-oligosaccharides Generated from Guar Gum by Endo-β-mannanase (ManB-1601)

Size exclusion chromatography of short chain β-manno-oligosaccharides (GG-β-MOS) produced after endo-mannanase (ManB-1601) hydrolysis of guar gum resulted in seven (P1-P7) peaks. Electron spray ionization mass-spectrometry (ESI-MS) revealed P3, P4, P5 and P6 peaks as pentasaccharide (DP5), tetrasaccharide (DP4), trisaccharide (DP3) and disaccharide (DP2), respectively. DP2 and DP3 GG-β-MOS were structurally characterized by NMR (H and C), FTIR and XRD. DP2 GG-β-MOS was composed of two species (A) mannopyranose β-1,4 mannopyranose and (B) α-1,6-galactosyl-mannopyranose while, DP3 oligosaccharide showed presence of three species i.e. (A) α-d-galactosyl-β-d-mannobiose (galactosyl residue at reducing end), (B) α-d-galactosyl-β-d-mannobiose (galactosyl residue at non-reducing end) and (C) mannopyranose β-1,4 mannose β-1,4 mannopyranose. In batch fermentation, DP2 GG-β-MOS was preferred over DP3 by all Lactobacillus sp. except Lactobacillus casei var rhamnosus. DP2/DP3 and GG-β-MOS mixture inhibited the growth of enteropathogens in monoculture and co-culture fermentations, respectively. Fermentation of GG-β-MOS mixture by Lactobacillus sp. produced short chain fatty acids.