Extraction of water-soluble hemicelluloses from barley husks.

Heat treatment of barley husks was performed to extract arabinoxylan with high yield and high weight-averaged molecular mass (M(W)). Microwave irradiation was employed for initial screening of suitable residence times (2-15 min), temperatures (120-210 degrees C) and initial pH (3-13) of the reaction slurry. Microwave irradiation was shown to be a good method for predicting the effects of heat treatment on a larger scale using steam pretreatment. A M(W) of about 40,000 Da was achieved without the addition of chemicals, by both microwave irradiation and steam pretreatment, with a yield of about 9%. The yield was significantly increased by slightly increasing the severity factor. However, the M(W) decreased below 20,000 Da at severity factors above 3.7. Arabinosyl side groups were enzymatically hydrolysed from the arabinoxylan by alpha-L-arabinofuranosidase to a degree of 47%, demonstrating the ability to specifically alter the side group substitution of arabinoxylans with the use of enzymes.