Co-production of bioethanol and xylosaccharides from steam-exploded eucalyptus sawdust using high solid loads in enzymatic hydrolysis: Effect of alkaline impregnation

Abstract

In this work, Eucalyptus grandis sawdust was investigated as raw matter for the co-production of xylosaccharides (XS) and bioethanol by steam explosion pretreatment with and without a previous NaOH impregnation stage. The acetyl groups were completely removed in the NaOH impregnation step, which inhibited the autohydrolysis during the steam explosion pretreatment. The best results, in terms of XS recovery and glucan content in the pretreated substrate, were obtained when E. grandis was subjected to steam explosion at 200 °C for 10 min without alkaline impregnation. 76 kg of XS per ton of sawdust were obtained from the hemicellulosic hydrolysate and were mostly xylose or short xylo-oligosaccharides (XOS) (83% and 17%, respectively). High hydrolysis efficiencies were obtained using high solids loading (27%) with the steam pretreated material. High ethanol concentrations (75.6 g/L) and yields (259 L per ton of dry raw sawdust) were obtained by simultaneous saccharification and fermentation (SSF), representing a suitable strategy for ethanol production from eucalyptus sawdust.