Current Microbiology

, Volume 32, Issue 3, pp 119–123

Production of Cellulases by Aspergillus fumigatus and Characterization of One β-Glucosidase

  • Eduardo A.  Ximenes
  • Carlos R.  Felix
  • Cirano J.  Ulhoa

DOI: 10.1007/s002849900021

Cite this article as:
Ximenes, E., Felix, C. & Ulhoa, C. Curr Microbiol (1996) 32: 119. doi:10.1007/s002849900021

Abstract.

Aspergillus fumigatus produces substantial extracellular cellulases on several cellulosic substrates including simple sugars. Low glucose potentiates enzyme production, but most cellulose-induced cellulases are repressed by high glucose. As production of cellulase in a wide substrate range is unusual, the cellulolytic complex of this thermophilic fungus was investigated. A β-glucosidase was separated by gel filtration and ion-exchange chromatography. It migrated in native polyacrylamide gel as a single protein (130 kDa), which split under denaturing conditions into two smaller proteins having molecular masses of 90 kDa and 45 kDa. However, only the 90-kDa protein was active. Conventional chromatographic procedures were unsuccessful for the separation of these two proteins. Therefore, the 130-kDa protein was studied for its kinetic properties. It hydrolyzed p-nitrophenyl-β-D-glucopyranoside (p-NPG) and cellobiose, but not β-glucans, laminarin, and p-nitrophenyl-β-D-xilopyranoside. The optimal pH and temperature of p-NPG and cellobiose hydrolysis were 5.0 and 4.0, and 65°C and 60°C, respectively. The Km values, determined for cellobiose and p-NPG of hydrolysis, were 0.075 mM and 1.36 mM, respectively. Glucose competitively inhibited the hydrolysis of p-NPG. The Ki was 3.5 mM.

Copyright information

© Springer-Verlag New York Inc. 1996

Authors and Affiliations

  • Eduardo A.  Ximenes
    • 1
  • Carlos R.  Felix
    • 1
  • Cirano J.  Ulhoa
    • 1
  1. 1.Departamento de Biologia, 70.910.900 Universidade de Brasília, Brasília, DF, Brasil BR