eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2020-08-20 3 2a 36812 article Annapurna Jetty 1 Ch. Subhakar 1 K. Kranthi 1 Ravichandra P 1 Bioengineering and Environmental Centre, Indian Institute of Chemical Technology (CSIR), Tarnaka, Hyderabad - 500 007 India The present work describes and compares stirred tank reactor (STR) with bioreactor (STR) in cascade of 4 and 6 for protease production using Bacillus subtilis. This gives an insight into the physiological state/ performance of the reactor based on product formation. The specific activity of protease showed an increasing trend from shake flask to STR and cascade reactors of 4 & 6 series. In shake flask the maximum specific activity was recorded during 72 hours with 7.339 Units/ ml, whereas in STR an increased enzyme activity of 10.106 Units/ml. has been achieved during the same period. The increase in enzyme activity is 52% from shake flask to STR. Similarly when cascade of STR (4 & 6 series) were used the maximum specific activity in cascade of 4 series of reactor is 13.71 Units/ml and 14.1 Units/ml in 6 series of reactor. The maximum activity achieved in gradostat is 38% more when compared to STR. The high performance of the cascade reactors are explained keeping in view of the physiological state of addition of external initial inoculum/ biomass, which is different from STR. The increase in enzyme production might be due to physiological state of the organism with respect to its origin. The production achieved in 4^th bioreactor onwards is at steady state and the organism metabolic activity remains same irrespective of number of bioreactors in the series. https://www.biotech-asia.org/vol3no2a/cascade-operation-of-stirred-tank-reactors-for-alkaline-protease-production-by-bacillus-subtilis/ Bioreactors; Bacillus subtilis; Gradostat; Protease; STR