Lower temperature pretreatment of wheat straw for high production of fermentable sugars using ball-milling combined with deep eutectic solvent

Deep eutectic solvent (DES) pretreatment of lignocellulose accompanied by high temperature and strong acid conditions, caused excessive degradation of hemicellulose and subsequently reduced yield of fermentable sugars. Mechanochemical pretreatment based on ball-milling (BM) and DES was designed to deconstruct wheat straw at moderate temperatures (50–60 °C) for enzymatic hydrolysis. High glucose and xylose yield of 99.71 % and 92.77 % were achieved for 72 h after BM assisted with choline chloride/oxalic acid (CO) treatment. This ascribes to the synergy of ball-milling and DES resulting in the loosening and collapse of lignocellulosic structures, leading to the selective removal and modification of hemicellulose and lignin. Relative saccharification activity of glucose and xylose was increased by 294.82 % and 658.41 % pretreated with BM and CO sequentially as compared with raw wheat straw, because of reduced crystallinity and increased of surface area and reducing-end concentration of pretreated wheat straw. Energy efficiency of ternary DES (CEO) system was 1.33 times that for the binary DES (CO) system during sequential treatment of BM and DES. Relative saccharification activity and energy consumption (or energy efficiency) was fitted as quadratic functions. This green and effective pretreatment method provides new insights for the lignocellulosic deconstruction.