Modelling and simulation of cellulase adsorption and recycling during enzymatic hydrolysis of cellulosic materials

Bader, Jörg; Bellgardt, K.‐H.; Singh, Ajay; Kumar, Pranav; Schügerl, K.

doi:10.1007/bf00369552

Cited by 15 publications

(4 citation statements)

References 17 publications

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“…Moreover, substrate is typically not in excess relative to cellulose-hydrolyzing activity (including cell-associated activity) in natural environments featuring microbial cellulose degradation (see "Uptake and phosphorylation of cellulose hydrolysis products" above). At cellulase loadings typical of engineered processes, it is commonly observed that free cellulase activity is present throughout the course of hydrolysis (24,306,506,694,773), which is indicative of accessible substrate sites not being in excess. As developed below and summarized in "Contrast to soluble substrates," the relative rarity of substrate-excess conditions underlies several distinctive features of enzymatically mediated hydrolysis of cellulose compared to enzymatically mediated reactions involving soluble substrates.…”

Section: Adsorptionmentioning

confidence: 99%

Microbial Cellulose Utilization: Fundamentals and Biotechnology

Lynd

Weimer

Zyl³

et al. 2002

Microbiol Mol Biol Rev

4,046

2,868

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Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for “consolidated bioprocessing” (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts

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Section: Adsorptionmentioning

confidence: 99%

Microbial Cellulose Utilization: Fundamentals and Biotechnology

Lynd

Weimer

Zyl³

et al. 2002

Microbiol Mol Biol Rev

4,046

2,868

View full text Add to dashboard Cite

show abstract

“…Ohmine et al [14] Selected empirically based models because Michaelis-Menten equations did not predict the experimental results Holtzapple et al [15] Proposed an "insoluble substrate equivalent" of the Michaelis-Menten model by the inclusion of parameters to account for adsorption and substrate available to enzyme Fugii et al [16] Considered the possibility to assume constant substrate concentration during the reaction Bader et al [17] The adsorption of cellulases to the substrate is regulated by the law of mass action and is similar to Michaelis kinetics in explaining the binding of enzyme to substrate.…”

Section: Introductionmentioning

confidence: 99%

Cellulose Hydrolysis by Cellobiohydrolase Cel7A Shows Mixed Hyperbolic Product Inhibition

Bezerra

Dias

Fraga

et al. 2011

Appl Biochem Biotechnol

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In order to establish which are the contribution of linear (total), hyperbolic (partial) or parabolic inhibitions by cellobiose, and also a special case of substrate inhibition, the kinetics of cellobiohydrolase Cel7A obtained from Trichoderma reesei was investigated. Values of kinetic parameters were estimated employing integrated forms of Michaelis-Menten equations through the use of non-linear regression, and criteria for selecting inhibition models are discussed. With cellobiose added at the beginning of the reaction, it was found that cellulose hydrolysis follows a kinetic model, which takes into account a mixed hyperbolic inhibition, by cellobiose with the following parameter values: K (m) 5.0 mM, K (ic) 0.029 mM, K (iu) 1.1 mM, k (cat) 3.6 h(-1) and k (cat') 0.2 h(-1). Cellulose hydrolysis without initial cellobiose added also follows the same inhibition model with similar values (4.7, 0.029 and 1.5 mM and 3.2 and 0.2 h(-1), respectively). According to Akaike information criterion, more complex models that take into account substrate and parabolic inhibitions do not increase the modulation performance of cellulose hydrolysis.

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“…The hydrolysis of insoluble, solid cellulose is a heterogeneous reaction, which does not match the assumptions of kinetic models based on Michaelis–Menten kinetics [13,14,20]. After an initial phase of adsorption of cellulases on cellulose, which is fast compared to hydrolysis [16,21–26], the enzymes cleave off cellobiose and move along the same chain, hydrolyzing glycosidic bonds until an event occurs that terminates cleavage. As the reaction proceeds to intermediate degrees of conversion, the rate of the reaction decreases dramatically, and the final part of cellulose hydrolysis requires an inordinate fraction of the overall total reaction time [27,28].…”

Section: Introductionmentioning

confidence: 99%

Cellulose crystallinity – a key predictor of the enzymatic hydrolysis rate

et al. 2010

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The enzymatic hydrolysis of cellulose encounters various limitations that are both substrate‐ and enzyme‐related. Although the crystallinity of pure cellulosic Avicel plays a major role in determining the rate of hydrolysis by cellulases from Trichoderma reesei, we show that it stays constant during enzymatic conversion. The mode of action of cellulases was investigated by studying their kinetics on cellulose samples. A convenient method for reaching intermediate degrees of crystallinity with Avicel was therefore developed and the initial rate of the cellulase‐catalyzed hydrolysis of cellulose was demonstrated to be linearly proportional to the crystallinity index of Avicel. Despite correlation with the adsorption capacity of cellulases onto cellulose, at a given enzyme loading, the initial enzymatic rate continued to increase with a decreasing crystallinity index, even though the bound enzyme concentration stayed constant. This finding supports the determinant role of crystallinity rather than adsorption on the enzymatic rate. Thus, the cellulase activity and initial rate data obtained from various samples may provide valuable information about the details of the mechanistic action of cellulase and the hydrolysable/reactive fractions of cellulose chains. X‐ray diffraction provides insight into the mode of action of Cel7A from T. reesei. In the conversion of cellulose, the (021) face of the cellulose crystal was shown to be preferentially attacked by Cel7A from T. reesei.

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Modelling and simulation of cellulase adsorption and recycling during enzymatic hydrolysis of cellulosic materials

Cited by 15 publications

References 17 publications

Microbial Cellulose Utilization: Fundamentals and Biotechnology

Microbial Cellulose Utilization: Fundamentals and Biotechnology

Cellulose Hydrolysis by Cellobiohydrolase Cel7A Shows Mixed Hyperbolic Product Inhibition

Cellulose crystallinity – a key predictor of the enzymatic hydrolysis rate

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