The control of gas phase, by periodic pressure oscillation coupled with forced aeration, was developed for improvement of cellulase production by Penicillium decumbens in solid-state culture (SSC). The effects of pressure oscillation amplitude, frequency, and airflow rate on cellulase production were investigated in detail. The technique was shown to be effective in the control of temperature in the substrate bed. The maximal temperature variation in the substrate bed was +1.5 degreesC of the set value (30 degreesC) under the operational strategy described above, while only +6.8 degreesC in static tray systems. At 30 degreesC, 4 atm, and an airflow rate of 71 min(-1), the maximal FPA and beta-glucosidase activities reached 17.7 IU g(-1) substrate dry matter (SDM) and 52.8 IU g(-1) substrate dry matter, respectively. Only 9.7 and 23.7 IU g(-1) substrate dry matter were obtained in static tray culture systems. (C) 2003 Elsevier Ltd. All rights reserved.