Softwood hemicellulose-degrading enzymes from Aspergillus niger: Purification and properties of a β-mannanase

• The enzymes needed for galactomannan hydrolysis, i.e. β-mannanase, α-galactosidase and β-mannosidase, were produced by the filamentous fungus Aspergillus niger. The β-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 β-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 β-mannanase was sequenced by Edman degradation, and comparison with Aspergillus aculeatus β-mannanase indicated high identity. The enzyme most probably lacks a cellulose binding domain since it was unable to adsorb on cellulose.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Keyword

Hemicellulase

α-Galactosidase

Aspergillus niger

β-Mannanase

Publication and Content Type

art (subject category)

ref (subject category)