The glucose oxidase system was adapted for estimation of the overall oxygen transfer rate in a periodic pressure oscillating, solid-state bioreactor. Enzyme concentration of 40 ml enzyme preparation L-1 was found adequate to give linear gluconic acid production and attain maximal oxygen absorption rates. At 4 atm and 30degreesC, the oxygen transfer rate reached 892 mmol kg(-1) initial dry matter h(-1) in this system, while only 121 mmol kg(-1) initial dry matter h(-1) was obtained in a conventional static tray bioreactor.