Abstract
Kanamycin B as the secondary metabolite of wild-type Streptomyces kanamyceticus (S. kanamyceticus) ATCC12853 is often used for the synthesis of dibekacin and arbekacin. To construct the strain has the ability for kanamycin B production; the pSET152 derivatives from Escherichia coli ET12567 were introduced to S. kanamyceticus by intergeneric conjugal transfer. In this study, we established a reliable genetic manipulation system for S. kanamyceticus. The key factors of conjugal transfer were evaluated, including donor-to-recipient ratio, heat-shock, and the overlaying time of antibiotics. When spores were used as recipient, the optimal conjugation frequency was up to 6.7 × 10(-6) . And mycelia were used as an alternative recipient for conjugation instead of spores; the most suitable donor-to-recipient ratio is 1:1 (10(7) :10(7) ). After incubated for only 10-12 hr and overlaid with antibiotics subsequently, the conjugation frequency can reach to 6.2 × 10(-5) which is sufficient for gene knockout and other genetic operation. Based on the optimized conjugal transfer condition, kanJ was knocked out successfully. The kanamycin B yield of kanJ-disruption strain can reach to 543.18 ± 42 mg/L while the kanamycin B yield of wild-type strain was only 46.57 ± 12 mg/L. The current work helps improve the content of kanamycin B in the fermentation broth of S. kanamyceticus effectively to ensure the supply for the synthesis of several critical semisynthetic antibiotics.