In a 250 ml-Erlenmeyer flask (containing coil) containing 50 ml of a production medium (0.5% soluble starch, 5% glucose, 0.5% yeast extract, 1.0% malt extract, and 5 μg/ml of thiopeptine) was inoculated a platinum loopful of AB10ΔB1 strain, and cultivated by shaking culture at 28° C. for 21 days. Then, to a portion (1 ml) of the culture medium were added 0.2 g of K2HPO4 and 0.2 ml of toluene, and the mixture was stirred vigorously to effect extraction. After centrifugation (3,000 rpm, 10 minutes), the toluene layer, which is an upper layer, was taken out and subjected to thin layer chromatography. As the thin layer chromatography plate was used Art 5715 (produced buy Merck Co.) and the developer used was ethyl acetate (75 ml):diethylamine (1.5 ml):water (1.5 ml):methanol (0.75 ml). After drying it, the plate was analyzed at 280 nm using Chromato Scanner (CS-930, produced by Shimazu Seisakusho), and the positions of spots were confirmed by color development by immersing the plate in 10% H solution and heating it at 105° C. for 5 minutes. Tylosin had an Rf (relative mobility) value of 0.62 while the product by the transformed strain contained 3-acetyltylosin at Rf=0.68 in addition to tylosin.
