Cellulose from Lignocellulosic Waste

Abstract

Bioconversion of renewable lignocellulosic biomass to biofuel and value-added products is globally gaining significant importance. Lignocellulosic wastes are the most promising feedstock considering its great availability and low cost. Biomass conversion process involves mainly two steps: hydrolysis of cellulose in the lignocellulosic biomass to produce reducing sugars and fermentation of the sugars to ethanol and other bioproducts. However, sugars necessary for fermentation are trapped inside the recalcitrant structure of the lignocellulose. Hence, pretreatment of lignocellulosic wastes is always necessary to alter and/or remove the surrounding matrix of lignin and hemicellulose in order to improve the hydrolysis of cellulose. These pretreatments cause physical and/or chemical changes in the plant biomass in order to achieve this result. Each pretreatment has a specific effect on the cellulose, hemicellulose, and lignin fraction. Thus, the pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis steps. In general, pretreatment methods can be classified into four categories, including physical, physicochemical, chemical, and biological pretreatment. This chapter addresses different pretreatment technologies envisaging enzymatic hydrolysis and microbial fermentation for cellulosic ethanol production and other bioproducts. It primarily covers the structure of lignocellulosic wastes; the characteristics of different pretreatment methods; enzymatic hydrolysis; fermentation and bioproducts; and future research challenges and trends.

Multi-step approach to add value to corncob: Production of biomass-degrading enzymes, lignin and fermentable sugars

“…Within hemicellulose, acetyl groups are the first to be hydrolyzed, followed by arabinan and xylan. This component (acetyl) of the side chains of the xylan backbone facilitates the autohydrolysis effect in LHW (Michelin et al, 2015).…”

“…Common wheat and spelt, barley, grain maize and corn-cob-mix accounted for a high share (86% in 2015) of the cereals produced in the EU-28 (EUROSTAT, 2017). These harvests generate a large amount of lignocellulosic residues that mainly consist of cellulose (30%-50%), hemicellulose (15%-35%) and lignin (10%-20%) that are linked with each other (Michelin et al, 2015).…”

“…Liquid hot water (LHW) pretreatment or autohydrolysis (hydrothermal processing) allows a high recovery of hemicelluloses as soluble saccharides, while both cellulose and lignin could be recovered in the solid phase as essentially non-degraded polymers. Furthermore, it has many technological and environmental benefits, mainly related to its non-catalyzed nature, as well as limited equipment corrosion problems, reduction of operational costs, and lower byproducts generation, such as furfural and hydroxymethylfurfural (Michelin et al, 2015;Michelin and Teixeira, 2016).…”

Production of Biomass-Degrading Enzymes by Trichoderma reesei Using Liquid Hot Water-Pretreated Corncob in Different Conditions of Oxygen Transfer

“…In fact, lignocellulosic biomass has been considered a promising material for production of these enzymes because of its abundance, low cost and wide availability [6]. Besides, it has been shown that better performances are obtained when an enzyme complex is prepared from the same lignocellulosic material that is meant to be hydrolyzed by that complex [7][8][9].…”

“…Various types of lignocellulosic biomass, such as hardwood, bagasse, and straws, have been studied as inducer sources or fermentation substrate to improve the lignocellulosic enzyme production [10,11]. One of the ways to improve the production is to use pretreated biomass which can lead to an improvement in production and yield since the pretreatment breaks the lignocellulosic structure and makes cellulose and hemicellulose more accessible for the fermenting microorganisms [7,8]. Hydrothermal pretreatment, such as liquid hot water (LHW), has been considered a suitable and costeffective pretreatment for biomass fractionation.…”