Impact of dilution rate on CGTase activity and productivity from an alkalophilic Bacillus sp. G1 in continuous culture

Abstract

Cyclodextrin glucanotransferase (CGTase) production by a locally isolated bacteriaBacillus sp. G1 was investigated in continuous culture with different dilution rates (D) (0.03,0.05, 0.07, 0.1, 0.3 and 0.5h-1). The CGTase activity profile was successfully maintained atsteady state using dilution rates of 0.03 to 0.3h-1. Maximum CGTase activity was obtained atlow dilution rate range (0.03-0.07h-1). CGTase activity decreased from 26.4 to 12.4 U/mlwhen the dilution rate was increased to 0.3h-1. The critical dilution rate (Dc) was establishedto be at dilution rate greater than 0.3h-1 and that the maximum CGTase productivity (Rmax)(3.72 U/ml/h) was achieved at 0.3h-1 dilution rate. This represented an increase of CGTaseproductivity by 4.8 times than that obtained at the dilution rate of 0.03h-1. We conclude thatthe CGTase productivity in steady state continuous culture can be readily achieved and thatthe impact of dilution rate is significant on activity and productivity.