Influence of dissolved oxygen and shear conditions on clavulanic acid production by Streptomyces clavuligerus

Clavulanic acid (CA), a potent beta-lactamase inhibitor, is produced by a filamentous bacterium. Here, the effect of DO and shear, expressed as impeller tip velocity, on CA production was examined. Cultivations were performed in a 4 L fermentor with speeds of 600, 800 and 1,000 rpm and a fixed air flow rate (0.5 vvm). Also, cultivation with automatic control of dissolved oxygen, at 50% air saturation, by varying stirrer speed and using a mixture of air and O-2 (10% v/v) in the inlet gas, and a cultivation with fixed stirrer speed of 800 rpm and air flow rate of 0.5 vvm, enriched with 10% v/v O-2, were performed. Significant variations in CA titer, CA production rate and O-2 uptake-rate were observed. It was also found that the DO level has no remarkable effect on CA production once a critical level is surpassed. The most significant improvement in CA production was related to high stirrer speeds.