Characterization of sugar beet pulp derived oligosaccharides

Abstract This thesis aimed at characterizing complex mixtures of sugar beet pulp derived oligosaccharides, in order to be able to monitor and optimize the enzymatic saccharification of sugar beet pulp. Hydrophilic interaction chromatography with on-line evaporative light scattering detection and multidimensional mass spectrometry (HILIC-ELSD-MSn) was developed as a versatile technique for the characterization of a wide range of neutral and acidic plant cell wall derived oligosaccharides. It was shown that the separation capacity of HILIC for acidic oligosaccharides outperforms other techniques. HILIC-MSn enabled efficient sequence elucidation of oligosaccharides in complex mixtures. The enzymatic saccharification of sugar beet pulp was optimized to release the maximum amounts of monomeric galacturonic acid and arabinose with limited concomitant degradation of cellulose, using conditions that are feasible for industrial upscaling. The oligosaccharides that were obtained after hydrolysis were characterized, thereby enabling recognition of enzyme activities additionally needed for the full degradation of recalcitrant oligosaccharides. The in vitro fermentation characteristics of sugar beet pectic oligosaccharides (SBPOS) were studied using human and pig fecal inocula. The fate of the different classes of SBPOS, the production of short-chain fatty acids and the changes in human fecal bacterial populations during in vitro fermentation were described. Several modifications in the microbiota composition that are potentially beneficial to host health were observed. HILIC was also coupled to traveling-wave ion mobility mass spectrometry to enable the simultaneous separation and characterization of complex mixtures of various isomeric pectic oligosaccharides. The developed method was used to characterize isomeric sugar beet rhamnogalacturonan I derived oligosaccharides carrying a glucuronic acid substituent, thereby identifying novel structural features of sugar beet pectin.