Comparative Study of Alkali and Acidic Cellulose Solvent Pretreatment of Corn Stover for Fermentable Sugar Production (original) (raw)
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Biotechnology and …, 2009
Liberation of fermentable sugars from recalcitrant biomass is among the most costly steps for emerging cellulosic ethanol production. Here we compared two pretreatment methods (dilute acid, DA, and cellulose solvent and organic solvent lignocellulose fractionation, COSLIF) for corn stover. At a high cellulase loading [15 filter paper units (FPUs) or 12.3 mg cellulase per gram of glucan], glucan digestibilities of the corn stover pretreated by DA and COSLIF were 84% at hour 72 and 97% at hour 24, respectively. At a low cellulase loading (5 FPUs per gram of glucan), digestibility remained as high as 93% at hour 24 for the COSLIF-pretreated corn stover but reached only $60% for the DA-pretreated biomass. Quantitative determinations of total substrate accessibility to cellulase (TSAC), cellulose accessibility to cellulase (CAC), and non-cellulose accessibility to cellulase (NCAC) based on adsorption of a nonhydrolytic recombinant protein TGC were measured for the first time. The COSLIF-pretreated corn stover had a CAC of 11.57 m 2 /g, nearly twice that of the DA-pretreated biomass (5.89 m 2 /g). These results, along with scanning electron microscopy images showing dramatic structural differences between the DA-and COSLIF-pretreated samples, suggest that COSLIF treatment disrupts microfibrillar structures within biomass while DA treatment mainly removes hemicellulose. Under the tested conditions COSLIF treatment breaks down lignocellulose structure more extensively than DA treatment, producing a more enzymatically reactive material with a higher CAC accompanied by faster hydrolysis rates and higher enzymatic digestibility.
Biotechnology and Bioengineering, 2009
Liberation of fermentable sugars from recalcitrant biomass is among the most costly steps for emerging cellulosic ethanol production. Here we compared two pretreatment methods (dilute acid, DA, and cellulose solvent and organic solvent lignocellulose fractionation, COSLIF) for corn stover. At a high cellulase loading [15 filter paper units (FPUs) or 12.3 mg cellulase per gram of glucan], glucan digestibilities of the corn stover pretreated by DA and COSLIF were 84% at hour 72 and 97% at hour 24, respectively. At a low cellulase loading (5 FPUs per gram of glucan), digestibility remained as high as 93% at hour 24 for the COSLIF-pretreated corn stover but reached only ∼60% for the DA-pretreated biomass. Quantitative determinations of total substrate accessibility to cellulase (TSAC), cellulose accessibility to cellulase (CAC), and non-cellulose accessibility to cellulase (NCAC) based on adsorption of a non-hydrolytic recombinant protein TGC were measured for the first time. The COSLIF-pretreated corn stover had a CAC of 11.57 m2/g, nearly twice that of the DA-pretreated biomass (5.89 m2/g). These results, along with scanning electron microscopy images showing dramatic structural differences between the DA- and COSLIF-pretreated samples, suggest that COSLIF treatment disrupts microfibrillar structures within biomass while DA treatment mainly removes hemicellulose. Under the tested conditions COSLIF treatment breaks down lignocellulose structure more extensively than DA treatment, producing a more enzymatically reactive material with a higher CAC accompanied by faster hydrolysis rates and higher enzymatic digestibility. Biotechnol. Bioeng. 2009;103: 715–724. © 2009 Wiley Periodicals, Inc.
Cellulose, 2012
Since cellulose accessibility has become more recognized as the major substrate characteristic limiting hydrolysis rates and glucan digestibilities, cellulose solvent-based lignocellulose pretreatments have gained attention. In this study, we employed cellulose solvent-and organic solvent-based lignocellulose fractionation using two cellulose solvents: concentrated phosphoric acid [*85 % (w/w) H 3 PO 4 ] and an ionic liquid Butyl-3-methylimidazolium chloride ([BMIM]Cl). Enzymatic glucan digestibilities of concentrated phosphoric acid-and [BMIM]Cl-pretreated corn stover were 96 and 55 % after 72 h at five filter paper units of cellulase per gram of glucan, respectively. Regenerated amorphous cellulose by concentrated phosphoric acid and [BMIM]Cl had digestibilities of 100 and 92 %, respectively. Our results suggested that differences in enzymatic glucan digestibilities of concentrated phosphoric acid-and
Comparison of Chemical Pretreatment Methods for Cellulosic Biomass
APCBEE Procedia, 2014
The variety in physiochemical characteristics of cellulosic biomass reveals the need for pretreatment technologies to help in the rapid and efficient conversion of carbohydrate polymers into fermentable sugars. Suitable pretreatment methods enhance the enzymatic hydrolysis of biomass because of the crystalline structure of cellulose and the complex structure of lignin and hemicellulose. The choice of pretreatment method affects on the sugar yield, avoids the degradation of sugars derived from hemicellulose and minimize the formation of inhibitors for subsequent fermentation steps. A suitable process should minimize heat and power requirements to be cost effective in operation. The present review focuses on various chemical pretreatment methods for lignocellulosic biomass based on recent reports in literature. An analysis of the methods shows that the composition of biomass is the main factor in the selection of pretreatment method.
Bioresources, 2020
Lignin has been shown to be a recalcitrance factor in many biomass conversion studies. To better understand the effects of lignin on cellulose conversion, different lignin fractions were extracted from the same dilute acid pretreated corn stover by three sequential isolation methods, namely ethanol extraction, dioxane extraction, and enzyme purification. The physicochemical properties of each lignin fraction including molecular weight distribution, surface area, surface charge, and other structural features varied, depending on the isolation methods. All three lignin fractions had negative surface charges, and ethanol-extracted lignin carried the highest surface charges, followed by dioxane-extracted lignin and cellulase-purified residual lignin. These physicochemical properties of lignin fractions also resulted in different extent of inhibitory effects on enzymatic hydrolysis of microcrystalline cellulose (MCC). Dioxane-extracted lignin exhibited the highest inhibitory effect on glucose release from MCC, followed by the cellulase-purified residual lignin fraction and ethanol-extracted lignin. Furthermore, lignin fractions with higher contents of syringyl (S) substructure and β-O-4 aryl ether interunit linkages showed a stronger negative effect on cellulase hydrolysis of MCC.
Features of promising technologies for pretreatment of lignocellulosic biomass
Bioresource Technology, 2005
Cellulosic plant material represents an as-of-yet untapped source of fermentable sugars for significant industrial use. Many physio-chemical structural and compositional factors hinder the enzymatic digestibility of cellulose present in lignocellulosic biomass. The goal of any pretreatment technology is to alter or remove structural and compositional impediments to hydrolysis in order to improve the rate of enzyme hydrolysis and increase yields of fermentable sugars from cellulose or hemicellulose. These methods cause physical and/or chemical changes in the plant biomass in order to achieve this result. Experimental investigation of physical changes and chemical reactions that occur during pretreatment is required for the development of effective and mechanistic models that can be used for the rational design of pretreatment processes. Furthermore, pretreatment processing conditions must be tailored to the specific chemical and structural composition of the various, and variable, sources of lignocellulosic biomass. This paper reviews process parameters and their fundamental modes of action for promising pretreatment methods.
New lignocellulose pretreatments using cellulose solvents: a review
Journal of Chemical …
Non-food lignocellulosic biomass is the most abundant renewable bioresource as a collectable, transportable, and storable chemical energy that is far from fully utilized. The goal of biomass pretreatment is to improve the enzymatic digestibility of pretreated lignocellulosic biomass. Many substrate factors, such as substrate accessibility, lignin content, particle size and so on, contribute to its recalcitrance. Cellulose accessibility to hydrolytic enzymes is believed to be the most important substrate characteristic limiting enzymatic hydrolysis. Cellulose solvents effectively break linkages among cellulose, hemicellulose and lignin, and also dissolve highly-ordered hydrogen bonds in cellulose fibers accompanied with great increases in substrate accessibility. Here the history and recent advances in cellulose solvent-based biomass pretreatment are reviewed and perspectives provided for addressing remaining challenges. The use of cellulose solvents, new and existing, provides opportunities for emerging biorefineries to produce a few precursors (e.g. monosaccharides, oligosaccharides, and lignin) for the production of low-value biofuels and value-added biochemicals.
Study of Chemical and Enzymatic Hydrolysis of Cellulosic Material to Obtain Fermentable Sugars
Journal of Chemistry
The objective of this study was to evaluate the chemical and enzymatic hydrolysis using a factorial experimental design (23) in order to obtain fermentable sugars from cellulose-based material (CBM) usually used as pet litter. In assessing chemical hydrolysis, we studied the effect of temperature, in addition to H2SO4 concentration and reaction time, on the production of total sugars, reducing sugars, soluble lignin, carbohydrate profile, furfural (F), and hydroxymethyl furfural (HMF). We performed a response surface analysis and found that, at 100°C, 1% acid concentration, and 60 min reaction time, the yields of 0.0033 g reducing sugar/g biomass and 0.0852 g total sugars/g biomass were obtained. Under the above conditions, F is not generated, while HMF is generated in such a concentration that does not inhibit fermentation. We pretreated the CBM with H2SO4, NaOH, CaO, or ozonolysis, in order to evaluate the effectiveness of the enzymatic hydrolysis from the pretreated biomass, usin...
Carbohydrate Polymers, 2011
The current research investigates the use of acid and enzyme hydrolysis to produce glucose from pretreated rice straw, banana plant waste and corn cob, as a lignocellulosic materials, to be a source for ethanol production. The agricultural biomasses were first tested, then a laboratory experimental set-up was designed in order to perform the necessary conversions. The biomass materials were characterized to contain 57.46-85.28% holocellulose and 14.55-26.12% lignin. Conversion of the cellulose to glucose was achieved by pre-treatment method for the agricultural residues first applying chemical pulping and steam explosion method as well as microwave treatment then followed by two processes, namely acid hydrolysis and enzyme hydrolysis. Sulfuric acid, 5%, was used in acid hydrolysis and Trichoderma reesei cellulases in enzyme hydrolysis. These experiments demonstrated that glucose concentration differs according to the type of pre-treatment and type of hydrolysis. Conversion of the glucose to ethanol during fermentation was accomplished by the action of yeasts from Saccharomyces cerevisiae. Ethanol production in the culture sample was monitored using gas chromatography. The results indicate that ethanol can be made from the above mentioned residues in a different yield according to the pre-treatment and the glucose produced from the hydrolysis method.