| The synthesis of antibiotics in Streptomyces is very sensitive to the level of dissolved oxygen in fermentation media. Low dissolved oxygen decreases yield of antibiotics. In order to improve oxygen and enhance erythromycin production, Vitreoscilla hemoglobin gene (vgb) was transformed into Saccharopolyspora erythraea in this work. S.erythraea is an industrial strain of producing erythromycin. Cloning of vgb under the control of either the constitutive PmerR promoter or the constitutive PermE* promoter led to the production of biochemically active hemoglobin (VHb) in Streptomyces lividans TK24 transformed with these constructs. Based on pSET152, which contained the Streptomyces phageΦC31 attachment site for chromosomal integration and the oriT region which is necessary for conjugal transfer, plasmids pSPU240 and pSPU242 which cloned PmerR-vgb-to and PermE*-vgb-to respectively were constructed in this study. By conjugal transfer, Plasmid pSPU240 and pSPU242 were introduced to S.erythraea.We confirmed recombinants by antibiotic selection and PCR, and screened out the optimal strains D4 and U9 from the recombinants. Titer of D4 and U9 were increased by 15% and 11% respectively than the original strain. In the experiment of shake flask, vgb was successfully expressed in transformed strains under different conditions. For example, with rare oxygen supply, titer is also higher than that of the control strain. When the concentration of soybean oil increased from 0.4% to 1.2%, fermentation titer of the high-producing strain D4 was 6400μg/mL, increased by about 20% than the control strain at the original cultivation. PCR analysis indicated vgb had been integrated into the chromosome of S.erythraea, and CO binding difference spectrum analysis of recombinant strain D4 showed that active VHb protein has been expressed in S.erythraea. At the same time the recombinant strain was stable at the generation and yield, and suitable for industrial application.
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