Directed Breeding Of Avermectin Producing Strain And Mutant Metabolites

ABSTRACTIn this paper, Streptomyces avermitlis was used as experimental object.Using strain C514 as experimental strain, the factors that influenced C5-O methylation of avermectins were studied. The experimental results showed that the C5-O methylation of avermectins was regulated by the concentration of 5adenosylmethionine(SAM). The A components of avermectins increased when the concentration of SAM was high and the B components of avermectins increased when the concentration of SAM decreased.In the course of screening for high producing strains and high B components producing strains, strain #7, the original strain, was treated by NTG. By selecting strains that were sensitive to sulfanilamide and strains that were induced by methionine, a strain, M-2, which produced about 82% B components was obtained. The strain Pr27 that has a high avermectins producing capacity was obtained by the method of protoplast regeneration combined with the model of chlorocaeaium tolerance.In the course of strain screening, two mutational strains, El07 and #21, were obtained. The main metabolites they produced, ElO7a, 21-A and 21-B, were identified as Oligomycin A, Avermectin aglycone A2a and Avermectin aglycone Aia. The possible structures of two minor components, E107b and 21-C, was proposed.