Conversion of Lignocellulosic Material Into Fermentable Sugars

Asem Hassan Mohammed,Frank Behrendt Behrendt,Frank Jürgen Methner

doi:10.22153/kej.2016.05.006

Asem Hassan Mohammed, Frank Behrendt Behrendt + Show 1 more

Open Access

https://doi.org/10.22153/kej.2016.05.006

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Abstract

Enzymatic hydrolysis process of lignocellulosic biomass materials is difficult because of inherent structural features of biomass, which represents barriers that prevent complete hydrolysis; therefore, pretreatment techniques are necessary to render biomass highly digestible in enzymatic hydrolysis process. In this research, (non?) oxidative short-term lime pretreatment of willow wood was used. A weight of 11.40 g of willow wood was mixed with an excess of calcium hydroxide (0.4 g Ca(OH)2/g raw biomass) and water loading (15 g/g raw biomass). Lime pretreatment was carried out for various periods of time including 1, 2, 3.5, 5 and 6 h, with temperatures at 100, 113, 130, 147 and 1600C, and oxygen pressures as oxidativeagent (6, 9, 13.5, 17.8, 21 bar absolute). The optimization of both pretreatment and enzymatic hydrolysis were depended on the maximum overall yields of glucan and xylan after two processes of lime pretreatment and enzymatic hydrolysis. The optimal conditions of pretreatment were as follow: 1) 1.33 h, 1470C, 17.8 bar absolute, 0.26 g Ca(OH)2/g raw biomass. 2) 1.25 h, 155 0C, 21 bar absolute, 0.26 Ca(OH)2/g raw biomass. Furthermore, the optimal values for low impact factors such as water loading was 15 g/g raw biomass and particle size was less than 3 mm. The optimal conditions of enzymatic hydrolysis were as follow: Cellulase enzymeloading was 0.1 g /g glucan in raw biomass, at substrate concentration of 50 g/L during 72 h of enzymatic hydrolysis The yield of enzymatic hydrolysis under these conditions were as follow: 96.00 g glucan/100 g of glucan in raw biomass, and 65.00 g xylan/100 g xylan in raw biomass.

Highlights

Lignocellulosic biomass is the most widely available source of carbohydrates, which can be converted in to biofuel; this feedstock is not readily digestible, to overcome this difficulty, lignocellulose structure must be modified through pretreatment [1].There are three major components inlignocellulosic biomass which one, cellulose, hemicellulose and lignin
Enzymatic hydrolysis of lignocellulosic biomass has been shown to be limiting factor in the conversion of biomass to chemicals and fuels, this limitation is due to inherent structural features of biomass, which represents the barriers that prevent complete hydrolysis, to increase the enzymatic digestibility of lignocellulosic biomass, biomass must subject mechanically and chemically pretreatments
Oxidative short-term lime pretreatment is an effective method for improving lignocellulose digestibility, Partial removal of lignin allowed some of biomass of swelling, increased internal surface area, removes acetyl and the various uranic acid substitutions on hemicellulose and larger median pore volume, all of which enhanceenzyme accessibility to carbohydrate polymers

Summary

Introduction

Lignocellulosic biomass is the most widely available source of carbohydrates, which can be converted in to biofuel; this feedstock is not readily digestible, to overcome this difficulty, lignocellulose structure must be modified through pretreatment [1]. There are three major components inlignocellulosic biomass which one, cellulose, hemicellulose and lignin. Cellulose and hemicellulose are not directly available for bioconversion due to their intimate association with lignin [2]. Enzymatic hydrolysis of lignocellulosic biomass has been shown to be limiting factor in the conversion of biomass to chemicals and fuels, this limitation is due to inherent structural features (i.e., acetyl content, lignin content, crystallinity, surface area, particle size and pore volume) of biomass, which represents the barriers that prevent complete hydrolysis, to increase the enzymatic digestibility of lignocellulosic biomass, biomass must subject mechanically (reducing size ≤ 4 mm) and chemically (e.g., acid/ alkali treatment) pretreatments. The treated biomass will become more readily available to enzymatically hydrolysis of their sugars by cellulase and hemicellulase enzymes and the resulting sugars which can be fermented to ethanol or other biofuel by microorganisms via fermentation process [3].

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