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 beta-manno-oligosaccharides (GG-beta-MOS) produced after endomannanase (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-beta-MOS were structurally characterized by NMR (H-1 and C-13), FTIR and XRD. DP2 GG-beta-MOS was composed of two species (A) mannopyranose beta-1,4 mannopyranose and (B) alpha-1,6-galactosyl-mannopyranose while, DP3 oligosaccharide showed presence of three species i.e. (A) alpha-D-galactosyl beta-D-mannobiose (galactosyl residue at reducing end), (B) alpha-D-galactosyl-beta-D mannobiose (galactosyl residue at non-reducing end) and (C) mannopyranose beta-1,4 mannose beta-1,4 mannopyranose. In batch fermentation, DP2 GG-beta-MOS was preferred over DP3 by all Lactobacillus sp. except Lactobacillus casei var rhamnosus. DP2/DP3 and GG-beta-MOS mixture inhibited the growth of enteropathogens in monoculture and co-culture fermentations, respectively. Fermentation of GG-beta-MOS mixture by Lactobacillus sp. produced short chain fatty acids.