Xylanase and Ferulic Acid Esterase Production by a Wild Strain of Aspergillus terreus

S. B. Balogun, Joseph Gomes, Walter Steiner*

Institute of Biotechnology, Technical University of Graz, Petersgasse 12, A-8010 Graz, Austria

Article history:
Received October 11,1996 
Accepted December 19, 1996

Key words:
A. terreus, xylanase, ferulic acid esterase, media optimization

Summary:
The medium composition for the production of endo-xylanase and ferulic acid esterase in shake-flask cultures by Aspergillus terreus was optimized using statistical methods. The optimized medium composition for xylanase production was found to be 40 g L^-1 coarse corn cobs (c. 1-5 mm), 4.5 g L^-1 gelitaflex, 12 g L-1 NaNO₃, while that for ferulic acid esterase production was 12 g L^-1 oat spelt xylan, 6.4 g L^-1 soybean meal and 4 g L-1 NH₄NO₃. The optimized media and culture conditions gave a maximum of 538.3 U/mL i.e. 8973 nkat/ml xylanase and 0.7 U/mL i.e. 11.7 nkat/ml, ferulic acid esterase activities after 5-7 days shake cultures. In addition to xylanase and ferulic acid esterase activities, the culture filtrates exhibited low or appreciable levels of filter-paper cellulose, carboxymethyl cellulose, β-glucosidase, β-xylosidase and acetyl esterase activities. In a laboratory bioreactor (10 L) culture using fine corn cobs (0.25-0.50 mm), xylanase production was slightly better than in the parallel shake-flask cultures. The pH optima of xylanase, β-xylosidase and ferulic acid esterase were 5.0, 4.5 and 5.0-6.0, respectively. The optimum temperature for xylanase, β-xylosidase and ferulic acid esterase was 50 °C. Xylanase and β-xylosidase showed moderate pH and thermal stabilities.