Temperature and carbon source affect the production and secretion of a thermostable β-xylosidase by Aspergillus fumigatus

The effect of the temperature of growth and carbon source on the production and secretion of P-xylosidase (EC 3.2.1.37) by the thermotolerant fungi Aspergillus fumigatus was studied in submerged cultures. In cultures developed at optimal temperature (30 degreesC) the enzyme was predominantly cell-bound, while in cultures developed at higher temperature (42 degreesC), the P-xylosidase activity was predominantly found in the cell-free filtrates. The use of corn cob powder instead of xylan as substrate increased considerably the secretion of enzyme. The highest level of extracellular P-xylosidase (45 U/ml or 360 U/mg protein) was obtained in 3% corn cob cultures grown at 42 degreesC for 72 h. The partially purified enzyme was active and stable at high temperatures. The presence of high titres of beta-xylosidase activity in association with xylanase in the culture filtrates enhanced the efficiency of the pulp hydrolysis process. (C) 2002 Elsevier Ltd. All rights reserved.