Wheat bran biorefinery--a detailed investigation on hydrothermal and enzymatic treatment.

Due to the enormous quantities arising in the milling industry and its specific properties, wheat bran can be considered as a feedstock for future biorefineries. In the present work, a detailed investigation was carried out on the hydrothermal (140-200°C) and enzymatic treatment of wheat bran. After hydrothermal pretreatment and a subsequent enzymatic hydrolysis a glucose yield of 65% and 90% was achieved, respectively. Interestingly, the hemicelluloses could be disintegrated to monomers only to approx. 50%. About 70% of the proteins were dissolved, however, practically no free amino acids were obtained under given conditions. Severe treatment conditions induce elevated losses of some amino acids. Minerals could be extracted almost completely. To disintegrate fat into glycerol and fatty acids severe process conditions were necessary. The formation of undesired by-products such as furfural or hydroxymethylfurfural starts at approx. 180°C.