Xylo-sugars production by microwave-induced hydrothermal treatment of corncob: Trace sodium hydroxide addition for suppression of side effects

To overcome the recalcitrance of lignocellulose structures that hinders the robust bioconversion of biomass for bioethanol and lignin-coproduct productions, efficient approaches are needed to remove hemicelluloses. In this study, a microwave-induced hydrothermal pretreatment of corncob was developed to improve xylo-sugars (xylose, xylooligosaccharides and xylan) yields and to reduce the hemicelluloses loss by controlling NaOH and the severity factor. During this process, the severity factor ranged from 2.30 to 4.30 and the low concentration of NaOH below 0.32% were considered. The results showed that NaOH had a significant impact on xylo-sugars yields as well as the severity factor. The highest xylo-sugars yield of 88.71% was achieved when 0.005% NaOH was employed as the deacetylation agent and the severity factor was 4.00. Meanwhile, the unknown loss of hemicelluloses was limited to 1.51% (based on the total hemicelluloses in corncob) and the formation of furfural was also limited at the low level (1.72%). (C) 2017 Elsevier B.V. All rights reserved.