Enhanced production of an extracellular protease from Beauveria bassiana by optimization of cultivation processes

Statistics-based experimental design, response surface methodology was employed to investigate the effect of medium components on the production of extracellular protease from Beauveria bassiana A1. The optimum medium composition for protease production was found to be (in %, w/v): 0.72 shrimp shell powder, 0.60 soy powder, 0.19 sucrose and 0.68 yeast extract. This medium was projected to produce, theoretically, 281.14 U/ml. By using this medium, an experimental maximum protease activity of 280.72 U/ml in 7 days cultivation verified the applied methodology. Further studies on bioreactor production of protease were investigated in a 5 l stirred-tank and 30 l airlift bioreactors. In 5 l stirred-tank bioreactor, a maximum protease activity of 238.77 U/ml was attained in 6 days of cultivation when aeration rate and agitation speed were controlled at 0.6 vvm and 150 rpm, respectively. On the other hand, in 30 l airlift bioreactor the maximum protease activity of 283.84 U/ml was found with the controlled aeration rate of 0.9 vvm operated in a bubble column mode. This activity in the 30 l airlift bioreactor was close to that obtained from the shaker-flask cultivation study (280.72 U/ml). However, the duration of cultivation period using 30 l airlift bioreactor was shorter than the corresponding duration obtained from the shaker-flask cultivation by 4 days.