Effect of Periodic Dissolved Oxygen Fluctuations on Glutamate Fermentation in Scale-down Reactor

A laboratory scale one compartment scale down system was used to simulate dissolved oxygen (DO) gradients occurred in large scale. Rectangular DO oscillations were established by manipulating the rotation speed of impeller，at oscillations periods of 2 h，4 h and 6 h and DO ranging from 0 to 30%. The effect of oscillating DO on the glutamate fermentation process was investigated，particularly on the cell growth and productivity of the glutamate or lactate. Cultures carried out at constant DO 30% of air saturation were used for comparison. It was shown that Corynebacterium glutamicum preferred to use glucose for growth but not for product accumulation under oscillating DO condition. Oscillations at the shortest period tested (i.e.，2 h) resulted in higher final biomass concentration (10.03 g/L) and lower maximum specific growth rate(0.112 h-1)，glutamate production(23 g/L) and lactate accumulation(10.5 g/L) compared with cultures carried out at longer oscillations periods (4 h and 6 h).