Single-Step Microwave-assisted Hot Water Extraction of Hemicelluloses from selected Lignocellulosic Materials – a Biorefinery Approach Authors: Teklu M. Gezahegn a,b* , Malin Brodin b , Annie F. Chimphango a , Karin Øyaas b , Bård H. Hoff c , Johann F. Görgens a a: Stellenbosch University, Process Engineering Department, Stellenbosch 7602, South Africa b: Paper and Fibre Research Institute (PFI), Høgskoleringen 6B, NO-7491 Trondheim, Norway c: Norwegian University of Science and Technology (NTNU), Department of Chemistry, Høgskoleringen 5, NO-7491 Trondheim, Norway ABSTRACT The viability of single-step microwave-induced pressurized hot water conditions for co- production of xylan-based biopolymers and bioethanol from aspenwood sawdust and sugarcane trash was investigated. Extraction of hemicelluloses was conducted using microwave-assisted pressurized hot water system. The effects of temperature and time on extraction yield and enzymatic digestibility of resulting solids were determined. Temperatures between 170-200 °C for aspenwood and 165-195 °C for sugarcane trash; retention times between 8-22 minutes for both feedstocks, were selected for optimization purpose. Maximum xylan extraction yields of 66 and 50 %, and highest cellulose digestibilities of 78 and 74 %, were attained for aspenwood and sugarcane trash respectively. Monomeric xylose yields for both feedstocks were below 7 %, showing that the xylan extracts were predominantly in non-monomeric form. Thus, single-step microwave-assisted hot water method is viable biorefinery approach to extract xylan from lignocelluloses while rendering the solid residues sufficiently digestible for ethanol production. KEYWORDS: Lignocellulosic Biorefinery, Hemicellulose Extraction, Aspenwood, Sugarcane Trash, Microwave-assisted Pressurized Hot Water Method * Corresponding Author: Process Engineering Department, Stellenbosch University, Stellenbosch 7602, South Africa; Tel: +27-641950543 E-mail: 18935001@sun.ac.za (Mihiretu, G.T.) (Or, gezahegn_teklu@yahoo.com)