Valorization of peanut shells: Manufacture of bioactive oligosaccharides

Peanut shells were subjected to non-isothermal aqueous treatments to cause the partial breakdown of hemicelluloses into soluble oligosaccharides and lignin-derived compounds with high antioxidant activity. The effects of temperature on the chemical composition of the substrate and soluble reaction products were assessed. Under selected conditions (210°C, severity=4.09), the overall amount of poly- and oligo- saccharides present in the liquid phase reached 9.8g/L. This solution was refined by consecutive stages of discontinuous diafiltration, yielding a refined product containing about 72.4wt% of oligomers at a global yield of 8.5kg/100kg oven-dry PS. The purified products were characterized by HPLC, MALDI-TOF-MS and FTIR, confirming the major reaction products were saccharides made up of xylose with degrees of polymerization up to 17, substituted with acetyl and methylglucuronosyl groups, for which a number of pharmaceutical and food applications have been proposed. Solubilization of hemicelluloses in the treatments resulted in the production of solids enriched in cellulose and lignin suitable for further applications.