The chitinolytic activity of Penicillium janthinellum P9 was studied in shaken cultures and in a 3-l benchtop bioreactor by varying culture conditions such as initial medium pH, growth temperature, stirrer speed and aeration rate. In shaken flasks, the highest levels of enzyme activity (468 and 483 U.l(-1)) were obtained at a growth temperature of 24 degrees C and at an initial medium pH of 4.0, respectively. In the bioreactor, both agitation and aeration significantly influenced the enzyme production: the highest level of enzyme activity (497 U.l(-1)) was obtained at an impeller speed of 500 rpm and an aeration rate of 1.5 vvm. Culturing P. janthinellum P9 under optimised conditions led to an increase in the enzyme activity of ca. 65% (686 U.l(-1) as compared to the 415 U.l(-1) obtained under the initial culture conditions).