Microorganisms offer many potential advantages for biotechnological processes; however, realization of the promise of these organisms will require extensive research on cultivation methods at elevated pressures and temperatures. This study applied Bacillu subtilis (ATCC 6051a) in a pressurized bioreactor to investigate the microbial growth and enzyme productivity at temperatures between 37 and 47℃ and pressures of 10 atm and 22 atm without oxygen toxicity by controlling O₂ composition. The studies with B. subtilis revealed that increasing the pressure from 10 to 22 atm using 2% O₂ accelerated the production of extracellular enzymes at 37℃ for α-amylase and 42℃ for protease compared with the optimum conditions for this microorganism of 37℃ and 1 atm. The high cell density effect also was observed at 22 atm and 34℃ (2% O₂). In this case, the enzyme production was more effective because of the pressurized conditions.