Oxytetracycline production by immobilized Streptomyces rimosus

This study examined whether the production of oxytetracycline by Streptomyces rimosus TM-55 (CCRC 960061) would be improved with calcium alginate immobilization in submerged fermentation compared with free cells. Results showed that in 1-mL culture broth, free cells produced 121 to 124 microg of oxytetracycline, whereas immobilized cells produced 153 to 252 microg. Immobilization of the cells retarded the growth rate of S. rimosus but increased the length of the growth period and improved the oxytetracycline production. The specific oxytetracycline productivity was 33.3 to 34.2 mg in each gram of free dry cells and was 40.2 to 40.7 mg in immobilized dry cells. The optimum immobilization conditions were alginate 2% and bead diameter of 2.13 mm. Oxytetracycline production increased with increasing inoculum density but decreased with increasing bead diameter. Ethylenediaminetetraacetic acid or monovalent ions could react with calcium in the bead or replace it with sodium ion, thereby reducing the strength of the beads.