Overproduction of Erythromycin by Ultraviolet Mutagenesis and Expression of ermE Gene in Saccharopolyspora erythraea.

Abstract

Erythromycin is a macrolide antibiotic with broad-spectrum activity against gram-positive bacteria that stops protein synthesis by binding to 50s ribosomal subunit. Classical and recombinant strain improvement, such as application of ultraviolet (UV) mutagenesis and selection of overproduction mutant, is the most important and convenient method in enhancement of antibiotic production. In the present study, Saccharopolyspora erythraea was mutagenized using UV lights and selection by tylosin resistance mutant to improve yield of erythromycin. In other sides, to improve the erythromycin yield in mutant, effects of various parameters such as carbon concentration and ermE gene expression were analyzed. In primary selection, high erythromycin producing strains and high erythromycin producer mutant were isolated by plaque agar, and an increase of 87% was observed in tylosin resistance mutant compared to wild-type strain. In secondary selection, a mutant strain (RHU233) with a production of 1.39 mg erythromycin per mL was isolated in fermentation process, which was 20 times more productive than the wild type. In contrast, it was found that glycerol can be used as an alternate carbon source in enhancement of erythromycin production. Comparison of ermE gene expression in mutants RHU233 high producer mutant RHU233 and wild type in Escherichia coli detected in accumulation of soluble hexahistidine-ermE was up to 45% of total cell protein after 18 h in mutants RHU233. Metal-chelation chromatography yielded 126 mg of hexahistidine-ermE per liter of culture with a purity slightly >95% in mutants RHU233. Finally, these optimized conditions could be used for the commercial production of this unique antibiotic.