Isolation of Fully Synthetic Promoters for Gene Expression in Corynebacterium Glutamicum

Corynebacterium glutamicum is an important industrial organism that is widely used in the production of amino acids, nucleotides and vitamins. To extend its product spectrum and improve productivity, C. glutamicum needs to undergo further engineering, including the development of applicable promoter system. Here, we developed new synthetic promoters with various strengths in C. glutamicum. First, fully synthetic promoter library was constructed in which 70-bp length of promoter regions were randomized and green fluorescent protein (GFP) was used as a reporter protein. From promoter library, twenty highly fluorescent cells were isolated by FACS and their promoters were characterized through extensive analysis of DNA sequences and mRNA transcripts. Among twenty promoters, six promoters which have different strengths were selected and it was clearly confirmed that the levels of gene expression under 6 promoters have high correlation with the strengths of promoters. This is the first report of synthetic promoters constructed in C. glutamicum, and our screening strategy together with the use of synthetic promoters of various strengths will contribute to the future engineering of C. glutamicum