1. Softwood hemicellulose-degrading enzymes from Aspergillus niger: purification and properties of a beta-mannanase
- Author
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Folke Tjerneld, Arthur Varga, Henrik Stålbrand, Torbjörn Drakenberg, Pia Ademark, Vesa Harjunpää, and József Medve
- Subjects
Bioengineering ,Applied Microbiology and Biotechnology ,Substrate Specificity ,Mannans ,chemistry.chemical_compound ,Polysaccharides ,Mannosidases ,Mannobiose ,Hemicellulose ,Amino Acid Sequence ,Isoelectric Point ,Cellulose ,Ammonium sulfate precipitation ,Mannan ,Chromatography ,biology ,Sequence Homology, Amino Acid ,Chemistry ,Hydrolysis ,Aspergillus aculeatus ,Aspergillus niger ,beta-Mannosidase ,General Medicine ,biology.organism_classification ,Cellulose binding ,Wood ,Molecular Weight ,Biodegradation, Environmental ,Biochemistry ,Biotechnology - Abstract
The enzymes needed for galactomannan hydrolysis, i.e., beta-mannanase, alpha-galactosidase and beta-mannosidase, were produced by the filamentous fungus Aspergillus niger. The beta-mannanase was purified to electrophoretic homogeneity in three steps using ammonium sulfate precipitation, anion-exchange chromatography and gel filtration. The purified enzyme had an isoelectric point of 3.7 and a molecular mass of 40 kDa. Ivory nut mannan was degraded mainly to mannobiose and mannotriose when incubated with the beta-mannanase. Analysis by 1H NMR spectroscopy during hydrolysis of mannopentaose showed that the enzyme acts by the retaining mechanism. The N-terminus of the purified A. niger beta-mannanase was sequenced by Edman degradation, and comparison with Aspergillus aculeatus beta-mannanase indicated high identity. The enzyme most probably lacks a cellulose binding domain since it was unable to adsorb on cellulose.
- Published
- 1998