Enhancement of Ascomycin Production by Expression of Vitreoscilla Hemoglobin Gene in Streptomyces hygroscopicus
In order to solve the shortage of dissolved oxygen in the fermentation process of ascomycin (1),the Vitreoscilla hemoglobin gene (vgb) which encodes Vitreoscilla hemoglobin (VHb) was integrated into 1 producing strain Streptomyces hygroscopicus.The codon-optimized vgb gene was ligased with plasmid pSET-M,making it under the control of constitutive erythromycin resistance gene promoter (ermE*),to yield an recombinant plasmid pSET-vgb.Then,vgb gene was introduced into the genome ofS.hygroscopicus SIPI-FK520-1 through conjugal transfer to construct an engineering strain named SIPI-FK520-2.The RT-PCR analysis showed that vgb gene had been successfully expressed in the recombinant engineering strain.The biological activity of VHb in the recombinant strain was further detected and confirmed by CO-binding difference spectroscopy.Finally,the strain was cultured in a 5 L bioreactor.The results indicated that the level of dissolved oxygen in fermentation process was significantly improved,and the yield of 1 was increased by 38% compared to the wild strain,up to 1 269.7 mg/L.