title: Fungal secretomes enhance sugar beet pulp hydrolysis.
abstract: The recalcitrance of lignocellulose makes enzymatic hydrolysis of plant biomass for the production of second generation biofuels a major challenge. This work investigates an efficient and economic approach for the enzymatic hydrolysis of sugar beet pulp (SBP), which is a difficult to degrade, hemicellulose-rich by-product of the table sugar industry. Three fungal strains were grown on different substrates and the production of various extracellular hydrolytic and oxidative enzymes involved in pectin, hemicellulose, and cellulose breakdown were monitored. In a second step, the ability of the culture supernatants to hydrolyze thermally pretreated SBP was tested in batch experiments. The supernatant of Sclerotium rolfsii, a soil-borne facultative plant pathogen, was found to have the highest hydrolytic activity on SBP and was selected for further hydrolyzation experiments. A low enzyme load of 0.2 mg g(-1) protein from the culture supernatant was sufficient to hydrolyze a large fraction of the pectin and hemicelluloses present in SBP. The addition of Trichoderma reesei cellulase (1-17.5 mg g(-1) SBP) resulted in almost complete hydrolyzation of cellulose. It was found that the combination of pectinolytic, hemicellulolytic, and cellulolytic activities works synergistically on the complex SBP composite, and a combination of these hydrolytic enzymes is required to achieve a high degree of enzymatic SBP hydrolysis with a low enzyme load.
authors.affiliation: Department of Food Sciences and Technology, Food Biotechnology Laboratory, BOKU - University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Kracher
authors.forename: Damir
authors.initials: D
authors.lastname: Oros
authors.forename: Wanying
authors.initials: W
authors.lastname: Yao
authors.forename: Marita
authors.initials: M
authors.lastname: Preims
authors.forename: Iva
authors.initials: I
authors.lastname: Rezic
authors.forename: Dietmar
authors.initials: D
authors.lastname: Haltrich
authors.forename: Tonci
authors.initials: T
authors.lastname: Rezic
authors.forename: Roland
authors.initials: R
authors.lastname: Ludwig
mesh_terms: D027461:Beta vulgaris / Q000737:chemistry*; D002480:Cellulase / Q000378:metabolism*; D002482:Cellulose / Q000032:analysis / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D005658:Fungi / Q000201:enzymology* / Q000378:metabolism* / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D006868:Hydrolysis; D025282:Mycelium / Q000378:metabolism / Q000502:physiology; D010088:Oxidoreductases
chemical_list: D005656:Fungal Proteins; D002482:Cellulose; D010088:Oxidoreductases; D002480:Cellulase; D005947:Glucose
keywords: Cellulases; Hemicellulases; Neurospora crassa; Sclerotium rolfsii; Trametes multicolor