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Cellulase–lignin interactions—The role of carbohydrate-binding module and pH in non-productive binding

Paper ID Volume ID Publish Year Pages File Format Full-Text
17128 42644 2013 7 PDF Available
Title
Cellulase–lignin interactions—The role of carbohydrate-binding module and pH in non-productive binding
Abstract

•Cellulase binding to lignin was studied using monocomponent cellulases.•Cellulase binding to isolated spruce and wheat straw lignin was highly pH-dependent.•Electrostatic forces are suggested to contribute to unproductive binding.•Amino acids that mediate CBM–cellulose interaction contribute also to lignin-binding.•CBM interacts with lignin probably through hydrophobic interactions.

Non-productive cellulase adsorption onto lignin is a major inhibitory mechanism preventing enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding of enzyme–lignin interactions is essential for the development of enzyme mixtures and processes for lignocellulose hydrolysis. We have studied cellulase–lignin interactions using model enzymes, Melanocarpus albomyces Cel45A endoglucanase (MaCel45A) and its fusions with native and mutated carbohydrate-binding modules (CBMs) from Trichoderma reesei Cel7A. Binding of MaCel45A to lignin was dependent on pH in the presence and absence of the CBM; at high pH, less enzyme bound to isolated lignins. Potentiometric titration of the lignin preparations showed that negatively charged groups were present in the lignin samples and that negative charge in the samples was increased with increasing pH. The results suggest that electrostatic interactions contributed to non-productive enzyme adsorption: Reduced enzyme binding at high pH was presumably due to repulsive electrostatic interactions between the enzymes and lignin. The CBM increased binding of MaCel45A to the isolated lignins only at high pH. Hydrophobic interactions are probably involved in CBM binding to lignin, because the same aromatic amino acids that are essential in CBM–cellulose interaction were also shown to contribute to lignin-binding.

Keywords
EnzHR, enzymatic hydrolysis residue; MCC, microcrystalline cellulose; MaCel45A, Melanocarpus albomyces Cel45A; TrCel7A, Trichoderma reesei Cel7ALignocellulose; Non-productive binding; Lignin; Cellulase; CBM; Electrostatic interaction
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 53, Issue 5, 10 October 2013, Pages 315–321
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us