Fed-batch cultivation for the production of clavulanic acid by an immobilized Streptomyces clavuligerusmutant

In order to obtain high productivity of clavulanic acid, a newly-introduced carrier, polyurethane pellet (PUP) Z97-020 was used for the immobilization process. In a stirred-tank bioreactor, batch cultivation by Streptomyces clavuligerusKK immobilized on PUP Z97-020 gave about 3100 mg of clavulanic acid per litre, representing an increase of 200% in productivity compared with that by fed-batch cultivation of free cells (1500 mg/l). However, the clavulanic acid produced rapidly decomposed due to the pH change during batch cultivation. Fed-batch cultivation by immobilized S. clavuligerusKK gave an excellent level of clavulanic acid up to 3250 mg/l, a productivity increase of 220% compared with that by fed-batch cultivation of free cells. These results suggest that immobilization with PUP Z97-020 is a more effective process for the production of clavulanic acid and that the maintenance of pH by fed-batch cultivation with glycerol as a limiting substrate prevents the clavulanic acid from decomposing during the fermentation.