Enzymatic saccharification of sugar beet pulp for the production of galacturonic acid and arabinose; a study on the impact of the formation of recalcitrant oligosaccharides

• Published in: Bioresource technology 2013-01, Vol.128, p.518-525
• Main Authors: Leijdekkers, A.G.M., Bink, J.P.M., Geutjes, S., Schols, H.A., Gruppen, H.
• Format: Article
• Language: English
• Subjects: Arabinofuranosidase; Arabinose; Arabinose - chemical synthesis; Beta vulgaris - chemistry; Biological and medical sciences; Cellulose; Degradation; Enzyme Activation; Enzyme Stability; enzymes; ethanol-production; fermentation; Fundamental and applied biological sciences. Psychology; Hexuronic Acids - chemical synthesis; hydrolysis; Mass spectrometry; Monosaccharides - chemistry; Oligosaccharides; Pectin; Plant Extracts - chemistry; Polygalacturonase - chemistry; polysaccharides; pretreatment; Recalcitrant oligosaccharides; Residues; rhamnogalacturonan regions; Saccharification; Sugar beet pulp; Sugar beets
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2012.10.126

► Production of monomeric galacturonic acid and arabinose from sugar beet pulp. ► Saccharification conditions are used that are feasible for industrial upscaling. ► Release of 79% galacturonic acid and 82% arabinose with 17% cellulose degradation. ► Recalcitrant oligosaccharides obtained after hydrolysis are characterized in detail. ► Lacking enzyme activities for further increase of yield are being discussed. Enzymatic saccharification of sugar beet pulp was optimized on kg-scale 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. A selected mixture of pectinases released 79% of the galacturonic acid and 82% of the arabinose as monomers from sugar beet pulp while simultaneously degrading only 17% of the cellulose. The recalcitrant structures that were obtained after hydrolysis were characterized using mass spectrometry. The most abundant structures had an average degree of polymerization of 4–5. They were identified as partially acetylated rhamnogalacturonan-oligosaccharides, mostly containing a terminal galacturonosyl residue on both reducing and non-reducing end, partially methyl esterified/acetylated homogalacturonan-oligosaccharides, mostly containing methyl and acetyl esters at contiguous galacturonosyl residues and arabinan-oligosaccharides, hypothesized to be mainly branched. It could be concluded that especially rhamnogalacturonan-galacturonohydrolase, arabinofuranosidase and pectin acetylesterase are lacking for further degradation of recalcitrant oligosaccharides.