Continuous culture of immobilized Streptomyces cells for kasugamycin production

Continuous cultures of immobilized Streptomyces kasugaensis, a kasugamycin producer, were carried out an Celite beads. When using a prototype separato r for immobilized-cell separation and recycling, the continuous operation c ould not be sustained for an extended period as a result of an excessive lo ss ofimmobilized cells caused by the poor performance of the separator. Acc ordingly, the immobilized-cell separator was revised to provide better immo bilized-cell settling and thus recycling into the reactor. In a subsequent culture using the revised separator, a stable operation was maintained for over 820 h with a high kasugamycin productivity. The kasugamycin productivi ty ranged from 9.8 to 16.1 mg/L/h, which was about 14- to 23-fold higher th an that in a batch suspended-cell culture. When the original feeding medium concentration was doubled at the end of the continuous culture, the produc tivity became severely impaired for several reasons, which will be discusse d. An excessive formation of free cells and loss of immobilized cells throu gh the separator were also observed.