Effects on Lignin Redistribution in Eucalyptus globulus Fibres Pre-Treated by Steam Explosion: A Microscale Study to Cellulose Accessibility

Abstract

The objective of this study was to investigate structural changes and lignin redistribution in Eucalyptus globulus pre-treated by steam explosion under different degrees of severity (S0), in order to evaluate their effect on cellulose accessibility by enzymatic hydrolysis. Approximately 87.7% to 98.5% of original glucans were retained in the pre-treated material. Glucose yields after the enzymatic hydrolysis of pre-treated material improved from 19.4% to 85.1% when S0 was increased from 8.53 to 10.42. One of the main reasons for the increase in glucose yield was the redistribution of lignin as micro-particles were deposited on the surface and interior of the fibre cell wall. This information was confirmed by laser scanning confocal fluorescence and FT-IR imaging; these microscopic techniques show changes in the physical and chemical characteristics of pre-treated fibres. In addition, the results allowed the construction of an explanatory model for microscale understanding of the enzymatic accessibility mechanism in the pre-treated lignocellulose.

Approaching Self-Bonded Medium Density Fiberboards Made by Mixing Steam Exploded Arundo donax L. and Wood Fibers: A Comparison with pMDI-Bonded Fiberboards on the Primary Properties of the Boards

“…These panels, due to the chemical and morphological changes of the material, exhibit improved mechanical behavior. Specifically, lignocellulosic material treated by STEX results in a defibrillated pulp for which the fibers are thin and long [ 39 , 59 ], thus enhancing the compactness of the boards. Domínguez-Robles et al also related the increase in density to the decrease in the length and width of the fibers, and to the increase of fine elements as a consequence of the pretreatment, thus observing an improvement in mechanical strength with respect to boards made of untreated fibers [ 60 ].…”

Steam Explosion of Eucalyptus grandis Sawdust for Ethanol Production within a Biorefinery Approach

“…However, the quantification of furfural in this liquid stream did not explain the low xylan recovery values since, at most, only 1% of the potential furfural was recovered with respect to the original sawdust xylan composition. However, it is known that furans are partially lost as pretreatment volatiles or undergo condensation reactions forming acid-insoluble humins and/or pseudolignin [46,47]. Xylan removal from the pretreated solids increased with the pretreatment severity, but this was not accompanied by an increase in the xylan components (both monomeric and oligomeric) in the pretreatment liquor, indicating mass losses normally due to dehydration.…”

“…However, the quantification of furfural in this liquid stream did not explain the low xylan recovery values since, at most, only 1% of the potential furfural was recovered with respect to the original sawdust xylan composition. However, it is known that furans are partially lost as pretreatment volatiles or undergo condensation reactions forming acid-insoluble humins and/or pseudolignin [46,47].…”

Utility Aspects of Sugarcane Bagasse as a Feedstock for Bioethanol Production: Leading Role of Steam Explosion as a Pretreatment Technique

“…Therefore, the removal of biomass components such as hemicelluloses and lignin will lead to a significant increase in glucose yield after enzymatic hydrolysis [20]. This increase in yield can range from 20% to 85%, depending in many cases on the severity conditions used during SE [72]. Thus, the benefits of hydrolysis, apart from enhancing the extractability of lignin polymer, result in the enhancement of the biodegradability of the raw material.…”