A new kinetic model for heterogeneous (or spatially confined) enzymatic catalysis: Contributions from the fractal and jamming (overcrowding) effects

Xu, Feng; Ding, Hanshu

doi:10.1016/j.apcata.2006.10.014

Cited by 118 publications

(95 citation statements)

References 35 publications

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“…The mix contained extracellular Hypocrea jecorina (Trichoderma reesei) cellulases and Aspergillus oryzae CEL3A BG. Wild-type H. jecorina CEL7A CBH-I; recombinant H. jecorina CEL6A CBH-II, CEL7B EG-I, and CEL5A EG-II; as well as recombinant CEL3A were prepared as previously reported (14,44,45).…”

Section: Methodsmentioning

confidence: 99%

Inhibition of Cellulase-Catalyzed Lignocellulosic Hydrolysis by Iron and Oxidative Metal Ions and Complexes

Tejirian

2010

Appl Environ Microbiol

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101

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Enzymatic lignocellulose hydrolysis plays a key role in microbially driven carbon cycling and energy conversion and holds promise for bio-based energy and chemical industries. Cellulases (key lignocelluloseactive enzymes) are prone to interference from various noncellulosic substances (e.g., metal ions). During natural cellulolysis, these substances may arise from other microbial activities or abiotic events, and during industrial cellulolysis, they may be derived from biomass feedstocks or upstream treatments. Knowledge about cellulolysis-inhibiting reactions is of importance for the microbiology of natural biomass degradation and the development of biomass conversion technology. Different metal ions, including those native to microbial activity or employed for biomass pretreatments, are often tested for enzymatic cellulolysis. Only a few metal ions act as inhibitors of cellulases, which include ferrous and ferric ions as well as cupric ion. In this study, we showed inhibition by ferrous/ferric ions as part of a more general effect from oxidative (or redox-active) metal ions and their complexes. The correlation between inhibition and oxidation potential indicated the oxidative nature of the inhibition, and the dependence on air established the catalytic role that iron ions played in mediating the dioxygen inhibition of cellulolysis. Individual cellulases showed different susceptibilities to inhibition. It is likely that the inhibition exerted its effect more on cellulose than on cellulase. Strong iron ion chelators and polyethylene glycols could mitigate the inhibition. Potential microbiological and industrial implications of the observed effect of redox-active metal ions on enzymatic cellulolysis, as well as the prevention and mitigation of this effect in industrial biomass conversion, are discussed.

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Section: Methodsmentioning

confidence: 99%

Inhibition of Cellulase-Catalyzed Lignocellulosic Hydrolysis by Iron and Oxidative Metal Ions and Complexes

Tejirian

2010

Appl Environ Microbiol

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101

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“…In the recent decade or so, activity loss of adsorbed enzyme has been proposed as a possible reason for this. Adsorbed enzyme can become deactivated due to the following possible reasons: (1) the cellobiohydrolases become stuck on the substrate surface due to a crystalline defect, or when surrounding cellulose chains prevent further processive action (Valjamae et aI., 1998); (2) enzymes jam on the substrate: surface resulting in hydrolysis rate reduction (Xu and Ding, 2007); (3) negligibly reversible cellulase binding (Ma et aI., 2008) ; or (4) non-productive binding of adsorbed cellulase (Jalak and Valjamae, 2010) . Recently, real-time AFM imaging revealed that a significant portion of adsorbed Cellobiohydrolase 1 (CBH1) got stuck on the substrate surface and became inactivated thereafter (Igarashi et aI., 2009).…”

Section: Effect Of Activity Loss Of Adsorbed Enzyme On Cellulose Hydrmentioning

confidence: 99%

“…CBHl is the most abundant and important cellulase in hydrolysis of crystalline cellulose. The kinetics of purified CBHl reacting with cellulosic substrate have been extensively studied (Valjamae et aI., 1998;Xu and Ding, 2007), as have hydrolysis from reducing or non-reducing ends (Imai et aI., 1998;Stahlberg et aI., 1993), binding reversibility (Bothwell et aI., 1997;Kyriacou et aI., 1989;Ma et aI., 2008;Nidetzky et aI., 1994), synergism effects with other cellulase components (Irwin et aI., 1993;Mansfield et aI., 1999;Walker et aI., 1992), processivity (Kipper et aI., 2005;Medve et aI., 1998a) and shear deactivation of exoglucanase (Gunjikar et aI., 2001). …”

Section: Separating Cbhl From a Commercial Cellulase Mixturementioning

confidence: 99%

“…Such activity loss has been reported to be caused by: (1) the cellobiohydrolases becoming stuck on the substrate surface due to a crystalline defect or when surrounding cellulose chains prevent further processive action (Valjamae et aI., 1998); (2) enzyme jamming on the substrate surface resulting in hydrolysis rate reduction (Xu and Ding, 2007); (3) negligibly reversible cellulase binding (Ma et aI., 2008); or (4) non-productive binding of adsorbed cellulase (Jalak and Valjamae, 2010). Evidence of inactivation of adsorbed cellobiohydrolase 1 (CBH1) was presented in recent studies using atomic force microscopy (AFM) by Igarashi et ai.…”

Section: Introductionmentioning

confidence: 99%

“…The main cause for the rate reduction and low yield is not yet understood, and determining the primary mechanism will have important implications in the optimal design of an enzymatic hydrolysis process. Several possible reasons for the low rate and yield have been suggested in the literature: change of reactivity (Nidetzky and Steiner, 1993;Zhang et aI., 1999) and physical properties of substrate, such as crystallinity (Betrabet and Paralikar, 1977;Ooshima et al, 1983); change of specific surface area (SSA) during the reaction (Hong et aI., 2007); deactivation of enzyme as a result of mechanical mixing (Ganesh et aI., 2000;Ghadge et aI., 2005b;Kim et al ., 1982;Reese and Mandels, 1980); and inactivation of adsorbed enzymes (Jalak and Valjamae, 2010;Ma et aI., 2008;Valjamae et aI., 1998;Xu and Ding, 2007). A simplified scheme to produce ethanol from cellulosic substrate Nidetzky and Steiner (1993) and Zhang et ai.…”

Section: Introductionmentioning

confidence: 99%

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