title: Cellulose surface degradation by a lytic polysaccharide monooxygenase and its effect on cellulase hydrolytic efficiency.
abstract: Lytic polysaccharide monooxygenase (LPMO) represents a unique principle of oxidative degradation of recalcitrant insoluble polysaccharides. Used in combination with hydrolytic enzymes, LPMO appears to constitute a significant factor of the efficiency of enzymatic biomass depolymerization. LPMO activity on different cellulose substrates has been shown from the slow release of oxidized oligosaccharides into solution, but an immediate and direct demonstration of the enzyme action on the cellulose surface is lacking. Specificity of LPMO for degrading ordered crystalline and unordered amorphous cellulose material of the substrate surface is also unknown. We show by fluorescence dye adsorption analyzed with confocal laser scanning microscopy that a LPMO (from Neurospora crassa) introduces carboxyl groups primarily in surface-exposed crystalline areas of the cellulosic substrate. Using time-resolved in situ atomic force microscopy we further demonstrate that cellulose nano-fibrils exposed on the surface are degraded into shorter and thinner insoluble fragments. Also using atomic force microscopy, we show that prior action of LPMO enables cellulases to attack otherwise highly resistant crystalline substrate areas and that it promotes an overall faster and more complete surface degradation. Overall, this study reveals key characteristics of LPMO action on the cellulose surface and suggests the effects of substrate morphology on the synergy between LPMO and hydrolytic enzymes in cellulose depolymerization.
authors.affiliation: From the Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria.
authors.forename: Manuel
authors.initials: M
authors.lastname: Eibinger
authors.affiliation: Institute of Electron Microscopy and Nanoanalysis and.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ganner
authors.affiliation: From the Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria.
authors.forename: Patricia
authors.initials: P
authors.lastname: Bubner
authors.affiliation: Institute of Electron Microscopy and Nanoanalysis and.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Rošker
authors.affiliation: Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kracher
authors.affiliation: Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Haltrich
authors.affiliation: Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria, and.
authors.forename: Roland
authors.initials: R
authors.lastname: Ludwig
authors.affiliation: Institute of Electron Microscopy and Nanoanalysis and Graz Centre for Electron Microscopy, Steyrergasse 17, A-8010 Graz, Austria, harald.plank@felmi-zfe.at.
authors.forename: Harald
authors.initials: H
authors.lastname: Plank
authors.affiliation: From the Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria, Austrian Centre of Industrial Biotechnology, Petersgasse 14, A-8010 Graz, Austria bernd.nidetzky@tugraz.at.
authors.forename: Bernd
authors.initials: B
authors.lastname: Nidetzky
mesh_terms: D002480:Cellulase; D002482:Cellulose / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry*; D006868:Hydrolysis; D006899:Mixed Function Oxygenases / Q000737:chemistry*; D009492:Neurospora crassa / Q000201:enzymology; D010084:Oxidation-Reduction; D013499:Surface Properties
chemical_list: D005656:Fungal Proteins; D002482:Cellulose; D006899:Mixed Function Oxygenases; D002480:Cellulase
keywords: Atomic Force Microscopy (AFM); Biofuel; Cellulase; Cellulose; Copper Monooxygenase; GH61-AA9; Lytic Polysaccharide Monooxygenase (LPMO); Oxidative Cellulose Surface Degradation; Synergy