title: Combined application of plasma mutagenesis and gene engineering leads to 5-oxomilbemycins A3/A4 as main components from Streptomyces bingchenggensis.
abstract: Milbemycin oxime has been commercialized as effective anthelmintics in the fields of animal health, agriculture, and human infections. Currently, milbemycin oxime is synthesized by a two-step chemical reaction, which involves the ketonization of milbemycins A3/A4 to yield the intermediates 5-oxomilbemycins A3/A4 using CrO3 as catalyst. Due to the low efficiency and environmental unfriendliness of the ketonization of milbemycins A3/A4, it is imperative to develop alternative strategies to produce 5-oxomilbemycins A3/A4. In this study, the atmospheric and room temperature plasma (ARTP) mutation system was first employed to treat milbemycin-producing strain Streptomyces bingchenggensis, and a mutant strain BC-120-4 producing milbemycins A3, A4, B2, and B3 as main components was obtained, which favors the construction of genetically engineered strains producing 5-oxomilbemycins. Importantly, the milbemycins A3/A4 yield of BC-120-4 reached 3,890 ± 52 g/l, which was approximately two times higher than that of the initial strain BC-109-6 (1,326 ± 37 g/l). The subsequent interruption of the gene milF encoding a C5-ketoreductase responsible for the ketonization of milbemycins led to strain BCJ60 (∆milF) with the production of 5-oxomilbemycins A3/A4 and the elimination of milbemycins A3, A4, B2, and B3. The high 5-oxomilbemycins A3/A4 yield (3,470 ± 147 g/l) and genetic stability of BCJ60 implied the potential use in industry to prepare 5-oxomilbemycins A3/A4 for the semisynthesis of milbemycins oxime.
authors: Key Laboratory of Agriculture Biological Functional Gene of Heilongjiang Provincial Education Committee, Northeast Agricultural University, Harbin, 150030, People's Republic of China.
authors: Hai-Yan
authors: HY
authors: Wang
authors: Ji
authors: J
authors: Zhang
authors: Yue-Jing
authors: YJ
authors: Zhang
authors: Bo
authors: B
authors: Zhang
authors: Chong-Xi
authors: CX
authors: Liu
authors: Hai-Rong
authors: HR
authors: He
authors: Xiang-Jing
authors: XJ
authors: Wang
authors: Wen-Sheng
authors: WS
authors: Xiang
mesh_terms: D000871:Anthelmintics / Q000378:metabolism*; D017353:Gene Deletion; D042822:Genomic Instability; D018942:Macrolides / Q000378:metabolism*; D060847:Metabolic Engineering; D016296:Mutagenesis; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000871:Anthelmintics; D018942:Macrolides; C078973:milbemycin oxime