Streptomyces sp. GT20021503 was isolated from the stem of B. gymnorrhiza. Liquid organic medium 79 (dextrose 10 g, bacto peptone 10 g, casamino acids 1 g, yeast extract 2 g, NaCl 6 g, H₂O 1 L) (2 × 100 mL/flask) was inoculated with a suspension of mycelium and spores (about 1 × 1 cm) of the title strain grown on agar slants or agar plates (oatmeal 20 g, agar 18 g, H₂O 1 L, pH 7.2,). After incubation for 48 h on a rotary shaker at 28 ℃, the culture was transferred to 3200 mL of medium 2 (oatmeal 20 g, CaCl₂ 5.7 × 10^-3 g, Fe-citrate 2.5 × 10^-3 g, MnSO₄ 5.0 × 10^-4 g, ZnCl₂ 2.5 × 10^-4 g, CuSO₄ 4.0 × 10^-5 g, Na₂B₄O₂ 5.0 × 10^-5g, CoCl 1.0 × 10^-5 g, NaMoO₄ 2.1x 10^-5g, H₂O 1 L, pH 7.8) (eight 1000 mL-scale Erlenmeyer flasks with 400 mL of medium 2 each) and incubated at 28 ℃ under shaking conditions for 48 h to yield prefermentation culture, which was poured into a 300 L-scale fermenter filled with 200 L of medium 2 and fermented for 5 days.