Production of Oligosaccharides from Agrofood Wastes

The development of biorefinery processes to platform chemicals for most lignocellulosic substrates, results in side processes to intermediates such as oligosaccharides. Agrofood wastes are most amenable to produce such intermediates, in particular, cellooligo-saccharides (COS), pectooligosaccharides (POS), xylooligosaccharides (XOS) and other less abundant oligomers containing mannose, arabinose, galactose and several sugar acids. These compounds show a remarkable bioactivity as prebiotics, elicitors in plants, food complements, healthy coadyuvants in certain therapies and more. They are medium to high added-value compounds with an increasing impact in the pharmaceutical, nutraceutical, cosmetic and food industries. This review is focused on the main production processes: autohydrolysis, acid and basic catalysis and enzymatic saccharification. Autohydrolysis of food residues at 160-190 degrees C leads to oligomer yields in the 0.06-0.3 g/g dry solid range, while acid hydrolysis of pectin (80-120 degrees C) or cellulose (45-180 degrees C) yields up to 0.7 g/g dry polymer. Enzymatic hydrolysis at 40-50 degrees C of pure polysaccharides results in 0.06-0.35 g/g dry solid (DS), with values in the range 0.08-0.2 g/g DS for original food residues.