Fig. 2
Construction of the FFA-sensing plasmid and its performance. a The plasmid map of the fatty acid biosensor (pFAB); tetA: tetracycline resistance gene; rfp: red fluorescent gene; Ampr: ampicillin resistance gene. b Effect of extracellular FFA concentrations on cell growth. At 40 µg/mL of tetracycline, SBF01 was cultivated with different concentrations of oleic acid (mM) [2 (filled circle), 1 (filled square), 0.5 (filled triangle), 0.1 (filled diamond), and 0 (open circle)]. c Screening efficiency. The strains SBF02 and SBF05 were cultivated in the 19:1 ratio to confirm that the FFA-overproducing cells were dominant in enrichment culture condition containing 40 µg/mL of tetracycline. The population of SBF05 was determined by colony PCR and DNA sequencing of the fadE locus of 15 randomly picked colonies after every enrichment cycle. Error bars mean standard deviations of three independent experiments