Extraction of water-soluble hemicelluloses from barley husks

Abstract

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 °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 α- l-arabinofuranosidase to a degree of 47%, demonstrating the ability to specifically alter the side group substitution of arabinoxylans with the use of enzymes.