Improved production of clavulanic acid by reverse engineering and overexpression of the regulatory genes in an industrial Streptomyces clavuligerus strain
Genomic analysis of the clavulanic acid (CA)-high-producing Streptomyces clavuligerus strains, OL13 and OR, developed through random mutagenesis revealed a frameshift mutation in the cas1 gene-encoding clavaminate synthase 1. Overexpression of the intact cas1 in S. clavuligerus OR enhanced the CA titer by approximately 25%, producing ~ 4.95 g/L of CA, over the OR strain in the flask culture. Moreover, overexpression of the pathway-specific positive regulatory genes, ccaR and claR, in the OR strain improved CA yield by approximately 43% (~ 5.66 g/L) in the flask. However, co-expression of the intact cas1 with ccaR-claR did not further improve CA production. In the 7 L fermenter culture, maximum CA production by the OR strain expressing the wild-type cas1 and ccaR-claR reached approximately 5.52 g/L and 6.01 g/L, respectively, demonstrating that reverse engineering or simple rational metabolic engineering is an efficient method for further improvement of industrial strains.
KeywordsClavulanic acid Streptomyces clavuligerus Reverse engineering Metabolic engineering
This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean Government (MSIT) (2015K1A1A2028365, 2019R1A2B5B03069338), Bio and Medical Technology Development Program (2018M3A9F3079662, 2018M3A9F3079664) through NRF funded by MSIT, and the Intelligent Synthetic Biology Center of the Global Frontier Project funded by MSIT (20110031961).
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