Sugar production from barley straw biomass pretreated by combined alkali and enzymatic extrusion

Abstract

A pretreatment that combines a thermo-mechanical process (extrusion) with chemical and biological catalysts to produce fermentable sugars from barley straw (BS) biomass was investigated. BS was firstly extruded with alkali and then, the pretreated material (extrudate) was submitted to extrusion with hydrolytic enzymes (bioextrusion). The bioextrudate was found to have 35% (w/wdwb) of total solids in soluble form, partly coming from carbohydrate hydrolysis during bioextrusion. About 48% of soluble solids dry weight is comprised by sugars, mostly glucose and xylose. Further enzymatic hydrolysis of bioextrudate could be successfully carried out at high solid loading level of 30% (w/v), with sugar production yield of 32g glucose and 18g xylose/100g bioextrudate at 72h incubation (equivalent to 96 and 52g/l concentration, respectively). These results, together with the high level of integration of the process, indicate a great potential of this pretreatment technology for sugar production from lignocellulosic substrates.