Enzymatic Hydrolysis of Two-way Pretreated Sawdust of <i>Eucalyptus globulus</i> and <i>Cupressus lusitanica</i>

Abstract

Sawdust in Ethiopia, despite of its abundance, is not being properly utilized. Pre-treatment has been found to be crucial step before enzymatic hydrolysis of lignocellulosic resources to obtain sugars from such resources. Various pre-treatment methods have been developed to facilitate these bio-conversion processes. This research was aimed at investigating the effects of the combined pretreatments of steam and mild NaOH with white rot fungi (WRF) on sawdust samples from Eucalyptus globulus and Cupressus lusitanica were investigated. The amounts of losses of lignin, cellulose and hemicellulose contents of the pretreated sawdust samples were measured. Samples of the pretreated sawdust samples were then subjected to the enzymes from the hydrolytic wood rot fungi for hydrolysis into fermentable sugars. It was observed that lignin, cellulose and hemicellulose losses of the two sawdust types increased with the increasing incubation days but lignin and hemicellulose were preferentially degraded than cellulose. Sugar yield obtained from the sawdust pretreated in the combination of NaOH with WRF and steam with WRF was significantly higher compared to the yield obtained from the NaOH and steam alone pretreated sawdust samples. Pretreatment by the combination of NaOH with the wood rot fungi significantly modified the recalcitrance nature of the sawdust samples than when steam combined with the fungi. Similarly, with increasing enzymatic hydrolysis periods, sugar yields significantly increased. Higher sugar yields were obtained from sawdust samples of E. globulus than C. lusitanica. The ligninolytic and cellulolytic fungi tested resulted in a notable sugar yields indicating the possible application of the wood rot fungi in sugar production from lignocellulosic sawdust wastes which could be used for different industrial applications.