Several expression vectors are described for expression of the Vitreoscilla haemoglobin gene (vhb) in an industrial erythromycin-producing strain of Saccharopolyspora erythraea. Cloning of vhb under the control of either the thiostrepton-inducible promoter or the constitutive promoter led to the production of chemically active haemoglobin (VHb) in lividans TK24 transformed with these constructs. However, the plasmids could not be transformed into Transformants of and/or exconjugants were obtained using a novel shuttle vector comprised of vhb under the control of the promoter, the plasmid pIJ350 origin of replication, the thiostrepton-resistance gene (tsr) for selection, and the oriT region which is necessary for conjugal transfer. Increased plasmid stability in was obtained by construction of a vector for chromosomal integration. This vector contained the phage øC31 attachment site for chromosomal integration and vhb expressed under the promoter and was stably maintained in the chromosome of Shake-flask cultivations of the transformed strain with the chromosomally integrated vhb gene show that vhb is expressed in an active form. The corresponding amount of erythromycin produced in the vhb-expressing strain was approximately 60% higher relative to the original VHb-negative strain.


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