Partition of enzymes between the solvent and insoluble substrate during the hydrolysis of lignocellulose by cellulases

Xu, Feng; Ding, Hanshu; Osborn, David; Tejirian, Ani; Brown, Kimberly M.; Albano, William A.; Sheehy, Neil; Langston, James

doi:10.1016/j.molcatb.2007.10.004

Cited by 55 publications

(33 citation statements)

References 49 publications

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“…Although more effective enzymes with increased specific activity (Kumar and Wyman, 2008b,c;Merino Sandra and Cherry, 2007;Percival Zhang et al, 2006), better pretreatments (Kadam and Hsu, 1997;Wyman et al, 2005b), and improved hydrolysis/fermentation systems and conditions should reduce the enzyme requirement for cellulosic biomass saccharification (Lynd et al, 2005;Oehgren et al, 2007;Tu et al, 2007b;Wingren et al, 2003), additives such as non-catalytic proteins (Willies, 2007;Xu et al, 2008;Yang and Wyman, 2006;Zheng et al, 2008), surfactants (Alkasrawi et al, 2003;Helle et al, 1993;Kim et al, 1982Kim et al, , 2007Ooshima et al, 1986;Park et al, 1992;Wu and Ju, 1998), polymers Borjesson et al, 2007;Tjerneld et al, 1985), and polyelectrolytes (Feng et al, 1992) have been shown to significantly increase sugar yields and/or lower enzyme requirements to achieve a given yield (Alkasrawi et al, 2003;Castanon and Wilke, 1981;Yang and Wyman, 2006). The mechanism is still not entirely clear, but such additives have been thought to impede deactivation and/or unproductive binding, increase cellulose accessibility, and/or enhance enzyme activity (Eriksson et al, 2002;Huang et al, 2003;Kim et al, 2006;Mizutani et al, 2002;Sewalt et al, 1997;Yang and Wyman, 2006).…”

Section: Introductionmentioning

confidence: 99%

Effect of additives on the digestibility of corn stover solids following pretreatment by leading technologies

Kumar

Wyman²

2009

Biotech & Bioengineering

132

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Bovine serum albumin (BSA), Tween-20, and polyethylene glycol (PEG6000) were added to washed corn stover solids produced by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), dilute sulfuric acid (DA), lime, controlled pH, and sulfur dioxide (SO(2)) pretreatments and to untreated corn stover (UT) and pure Avicel glucan prior to adding cellulase supplemented with beta-glucosidase at an activity ratio of 1:2/g and a moderate enzyme loading of 16.1 mg/g glucan in the raw corn stover. The additives were applied individually at 150, 300, and 600 mg/g glucan in the pretreated solids and in combinations of equal amounts of each that totaled 600 mg/g. The greatest increase in total sugar release was by Tween-20 with SO(2) pretreated solids followed by PEG6000 with ARP solids and Tween-20 with lime solids. The effectiveness of the additives was observed to depend on the type of sugars left in the solids, suggesting that it may be more beneficial to use the mixture of these additives to realize a high total sugar yield. In addition, little enhancement in sugar release was possible beyond a loading of 150 mg additives/g glucan for most pretreatments, and combinations did not improve sugar release much over use of additives alone for all except SO(2). Additives were also found to significantly increase concentrations of cellobiose and cellooligomers after 72 h of Avicel hydrolysis.

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Section: Introductionmentioning

confidence: 99%

Effect of additives on the digestibility of corn stover solids following pretreatment by leading technologies

Kumar

Wyman²

2009

Biotech & Bioengineering

132

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“…AFEX produces inhibitory degradation compounds at a reduced level (12,13) and preserves nutrients in biomass (14) for fermentation. Residual ammonia further enriches the nutrient content of the AFEX-pretreated biomass.…”

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confidence: 99%

Cellulosic ethanol production from AFEX-treated corn stover using Saccharomyces cerevisiae 424A(LNH-ST)

Lau

Dale²

2009

Proc. Natl. Acad. Sci. U.S.A.

328

200

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Current technology using corn stover (CS) as feedstock, Ammonia Fiber Expansion (AFEX) as the pretreatment technology, and Saccharomyces cerevisiae 424A(LNH-ST) as the ethanologenic strain in Separate Hydrolysis and Fermentation was able to achieve 191.5 g EtOH/kg untreated CS, at an ethanol concentration of 40.0 g/L (5.1 vol/vol%) without washing of pretreated biomass, detoxification, or nutrient supplementation. Enzymatic hydrolysis at high solids loading was identified as the primary bottleneck affecting overall ethanol yield and titer. Degradation compounds in AFEX-pretreated biomass were shown to increase metabolic yield and specific ethanol production while decreasing the cell biomass generation. Nutrients inherently present in CS and those resulting from biomass processing are sufficient to support microbial growth during fermentation. This platform offers the potential to improve the economics of cellulosic ethanol production by reducing the costs associated with raw materials, process water, and capital equipment.AFEX ͉ fermentation ͉ Lignocellulose ͉ biofuel

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“…In the enzymatic conversion of biomass to sugars, enzymes, coadjuvant proteins and surfactants, all can adsorb to the substrates. [19][20][21][22][23][24] Divalent cations are also adsorbed onto cellulosic surfaces, which can act as ion exchangers. [25][26][27] The effect of adsorption equilibrium on the apparent diffusion coefficient in a homogeneous medium is described by 28,29 …”

Section: Porous Effmentioning

confidence: 99%

Magnetic resonance imaging to measure concentration profiles of solutes diffusing in stagnant beds of cellulosic fibers

2011

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in Wiley Online Library (wileyonlinelibrary.com).The evolution of the concentration profiles of an adsorbing solute diffusing in a stagnant bed of cellulosic fibers is measured using magnetic resonance imaging. Effective diffusivities are calculated by matching concentration profiles with a numerical model of one-dimensional Fickian diffusion. The measured values of the effective diffusion coefficients are interpreted using a model that accounts for the porosity, tortuosity, and adsorption equilibrium constant. The effective diffusivities in fiber beds are significantly lower than the bulk diffusivity of the solute and highly dependent on fiber type. The diffusivity is lower for the fiber type that exhibited stronger adsorption properties. The influence of concentration, adsorption, and other fiber characteristics on diffusion rates and rates of reaction is discussed.

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Partition of enzymes between the solvent and insoluble substrate during the hydrolysis of lignocellulose by cellulases

Cited by 55 publications

References 49 publications

Effect of additives on the digestibility of corn stover solids following pretreatment by leading technologies

Effect of additives on the digestibility of corn stover solids following pretreatment by leading technologies

Cellulosic ethanol production from AFEX-treated corn stover using Saccharomyces cerevisiae 424A(LNH-ST)

Magnetic resonance imaging to measure concentration profiles of solutes diffusing in stagnant beds of cellulosic fibers

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