Modeling Intrinsic Kinetics of Enzymatic Cellulose Hydrolysis

Peri, Suma; Karra, Srinivas; Lee, Y. Y.; Karim, M. Nazmul

doi:10.1021/bp060322s

Cited by 56 publications

(47 citation statements)

References 32 publications

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“…For example, by incorporating an explicit processive mechanism for CBH enzymes, we removed the previous assumption that CBH enzyme-substrate complexation was in equilibrium. This assumption, while commonly made in cellulase kinetic models (Holtzapple et al, 1984;Okazaki and Moo-Young, 1978;Peri et al, 2007;Wald et al, 1984;Zhang and Lynd, 2006), has no experimental support. The removal of this assumption results in the mechanism shown in Figure 1a.…”

Section: Mechanistic Model Developmentmentioning

confidence: 99%

A mechanistic model for rational design of optimal cellulase mixtures

Levine

Fox

Clark

et al. 2011

Biotech & Bioengineering

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A model-based framework is described that permits the optimal composition of cellulase enzyme mixtures to be found for lignocellulose hydrolysis. The rates of hydrolysis are shown to be dependent on the nature of the substrate. For bacterial microcrystalline cellulose (BMCC) hydrolyzed by a ternary cellulase mixture of EG2, CBHI, and CBHII, the optimal predicted mixture was 1:0:1 EG2:CBHI:CBHII at 24 h and 1:1:0 at 72 h, at loadings of 10 mg enzyme per g substrate. The model was validated with measurements of soluble cello-oligosaccharide production from BMCC during both single enzyme and mixed enzyme hydrolysis. Three-dimensional diagrams illustrating cellulose conversion were developed for mixtures of EG2, CBHI, CBHII acting on BMCC and predicted for other substrates with a range of substrate properties. Model predictions agreed well with experimental values of conversion after 24 h for a variety of enzyme mixtures. The predicted mixture performances for substrates with varying properties demonstrated the effects of initial degree of polymerization (DP) and surface area on the performance of cellulase mixtures. For substrates with a higher initial DP, endoglucanase enzymes accounted for a larger fraction of the optimal mixture. Substrates with low surface areas showed significantly reduced hydrolysis rates regardless of mixture composition. These insights, along with the quantitative predictions, demonstrate the utility of this model-based framework for optimizing cellulase mixtures.

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Section: Mechanistic Model Developmentmentioning

confidence: 99%

A mechanistic model for rational design of optimal cellulase mixtures

Levine

Fox

Clark

et al. 2011

Biotech & Bioengineering

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“…Refs. [83][84][85], and the results in Fig. 2 and supplemental Table S1 show that parameters estimated at different time scales may vary by orders of magnitude.…”

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confidence: 91%

Origin of Initial Burst in Activity for Trichoderma reesei endo-Glucanases Hydrolyzing Insoluble Cellulose

Murphy

Cruys-Bagger

Damgaard

et al. 2012

Journal of Biological Chemistry

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The kinetics of cellulose hydrolysis have longbeen described by an initial fast hydrolysis rate, tapering rapidly off, leading to a process that takes days rather than hours to complete. This behavior has been mainly attributed to the action of cellobiohydrolases and often linked to the processive mechanism of this exo-acting group of enzymes. The initial kinetics of endo-glucanases (EGs) is far less investigated, partly due to a limited availability of quantitative assay technologies. We have used isothermal calorimetry to monitor the early time course of the hydrolysis of insoluble cellulose by the three main EGs from Trichoderma reesei (Tr): TrCel7B (formerly EG I), TrCel5A (EG II), and TrCel12A (EG III). These endo-glucanases show a distinctive initial burst with a maximal rate that is about 5-fold higher than the rate after 5 min of hydrolysis. The burst is particularly conspicuous for TrCel7B, which reaches a maximal turnover of about 20 s ؊1 at 30°C and conducts about 1200 catalytic cycles per enzyme molecule in the initial fast phase. For TrCel5A and TrCel12A the extent of the burst is 2-300 cycles per enzyme molecule. The availability of continuous data on EG activity allows an analysis of the mechanisms underlying the initial kinetics, and it is suggested that the slowdown is linked to transient inactivation of enzyme on the cellulose surface. We propose, therefore, that the frequency of structures on the substrate surface that cause transient inactivation determine the extent of the burst phase.

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“…셀룰로스의 분해에서 생성되는 포도당과 cellubiose는 효소반응의 저해물 질로 작용하는 것이 알려져 있다 [13]. 저해작용이 있는 효소 속도 반응식은 용해성 기질을 사용할 때 Michaelis-Menten 속 도식을 변형하여 사용한다 [23].…”

Section: 서 론 바이오매스를 당(Sugar)으로 전환한 후 발효 혹은 화학적 변환에 의해 에탄올과 같은 액체 연료나 unclassified

Hydrolysis of Cellulose by Immobilized Cellulase in a Packed Bed Reactor

Kang¹,

Lee²

2013

Journal of Life Science

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Immobilized cellulase on weak ion exchange resin showed a typical Langmuir adsorption isotherm. Immobilized cellulase had better stability with respect to pH and temperature than free cellulase. Kinetics of thermal inactivation on free and immobilized cellulase followed first order rate, and immobilized cellulase had a longer half-life than free cellulase. The initial rate method was used to characterize the kinetic parameters of free and immobilized enzyme. The Michaelis-Menten constant Km was higher for the immobilized enzyme than it was for the free enzyme. The effect of the recirculation rate on cellulose degradation was studied in a recycling packed-bed reactor. In a continuous packed-bed reactor, the increasing flow rate of cellulose decreased the conversion efficiency of cellulose at different input lactose concentrations. Continuous operation for five days was conducted to investigate the stability of long term operation. The retained activity of the immobilized enzymes was 48% after seven days of operation.

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Modeling Intrinsic Kinetics of Enzymatic Cellulose Hydrolysis

Cited by 56 publications

References 32 publications

A mechanistic model for rational design of optimal cellulase mixtures

A mechanistic model for rational design of optimal cellulase mixtures

Origin of Initial Burst in Activity for Trichoderma reesei endo-Glucanases Hydrolyzing Insoluble Cellulose

Hydrolysis of Cellulose by Immobilized Cellulase in a Packed Bed Reactor

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