Investigations on a wheat bran biorefinery involving organosolv fractionation and enzymatic treatment

• Ethanol organosolv fractionation of wheat bran was investigated in detail.
• Enzymatic hydrolysis of the obtained fractions gave a glucose yield of 75%.
• Proteins could be extracted almost quantitatively.
• During the lignin precipitation step, proteins partially coprecipitated.

The present study elucidates the organosolv treatment of wheat bran, the major by-product of the milling industry. The influence of temperature (160–200 °C) and ethanol concentration (30–60% (w/w)) at a given process time of 30 min was investigated. Enzymatic treatments of the organosolv extracts including solid residues led to an overall glucose yield of 75%. The conversion of hemicelluloses into xylose and arabinose was approximately 60% and 45%, respectively. Proteins could be almost completely dissolved, however, practically no free amino acids were obtained. Surprisingly, only around 30% of lignin and 65% of minerals were dissolved. Severe treatment conditions induced the disintegration of fat into glycerol and fatty acids as well as the formation of sugar degradation products. During the lignin precipitation step, proteins partially coprecipitated.