Design of a synthetic miniR1 plasmid and its production by engineered Escherichia coli

A synthetic plasmid consisting of the minimal elements for replication control of the R1 replicon and kanamycin resistance marker, which was named pminiR1, was developed. pminiR1 production was tested at 30 °C under aerobic and microaerobic conditions in Escherichia coli W3110 recA- (W1). The plasmid DNA yields from biomass (YpDNA/X) were only 0.06 ± 0.02 and 0.22 ± 0.11 mg/g under aerobic and microaerobic conditions, respectively. As an option to increase YpDNA/X values, pminiR1 was introduced in an engineered E. coli strain expressing the Vitreoscilla hemoglobin inserted in chromosome (W12). The YpDNA/X values using strain W12 increased to 0.85 ± 0.05 and 1.53 ± 0.14 mg/g under aerobic and microaerobic conditions, respectively. pminiR1 production in both strains was compared with that of pUC57Kan at 37 °C under aerobic and microaerobic conditions. The YpDNA/X values for pminiR1 using strain W12 were 6.25 ± 0.16 and 9.27 ± 0.95 mg/g under aerobic and microaerobic conditions, respectively. Such yields were similar to those obtained for plasmid pUC57Kan using strain W12 (6.9 ± 0.64 and 10.85 ± 1.06 mg/g for aerobic and microaerobic cultures, respectively). Therefore, the synthetic minimal plasmid based on the R1 replicon is a valuable alternative to pUC plasmids for biotechnological applications.