Influence of doublecopy genes of aveC on avermectin production in Streptomyces avermitilis

Objective To enhance the production of avermectin component1 by increasing aveC copy in the chromosome of Streptomyces avermitilis.Methods Second copy of aveC was inserted into bkdAB in the genomic DNA of S.avermitilis by gene manipulation;recombinant strains were obtained by homologous DNA double cross-over,and the content of each component was detected by HPLC.Results It was testified that the second aveC copy was inserted exactly into the expected site.However,HPLC analysis of fermentation products produced by recombinant strains showed that the ratio of component 1 to component 2 changed indistinctively,while B1a potency of avermectin by recombinant strains enhanced markedly.Conclusions It implies that the activity of aveC gene product may not be the main factor for the ratio of component1 to component 2,but its activity might be a restrictive factor in the biosynthesis of avermectin in S.avermitilis.