초록
A process for hemicellulose fractionation and purification from wheat straw and bran has been investigated. The aim was to define the efficiency of a pilot scale process combining twin-screw extrusion and refining steps such as ultrafiltration and chromatography, to replace alcoholic precipitation. Extraction by twin-screw extrusion gave a complex extract containing only 22.7% carbohydrates. Evaporation (EV) followed by ethanol precipitation (P) and freeze-drying (FD), gave a 25.7% arabinoxylan yield with 24.1% arabinoxylan content. The other purification process studied was based on a combination of ultrafiltration (UF), anion exchange chromatography (CHR) and freeze-drying (FD), without precipitation. It gave a 24.3% yield of arabinoxylans into the hemicellulosic powders and 13.9% arabinoxylan content. Despite the obvious interest of using ultrafiltration for demineralization and anion exchange chromatography for decoloration, the purity of the final powder is still too low, because of difficulties in achieving separation of proteins and hemicelluloses and concentration of the solution, in the same step.