Fig. 6: Dynamic change of the residual safeguard strain during the second round of two successive 1-liter geraniol fermentation after switching growth conditions.

a Schematic diagram showing the experimental design. The multiplex safeguard strain (yXF281) was used in the first round of fermentation (72 h, indicated in blue) supplemented with 1 mM OMeY and 2% (w/v) galactose, followed by the second round of fermentation (144 h, indicated in khaki) using the wild-type derivative strain (yXF282) grown in non-permissive broth (without OMeY and 2% glucose) for yXF281. Both yXF281 and yXF282 strains were modified to produce geraniol. The medium used for different rounds of fermentation are indicated. Before the second round of fermentation, the equipment was washed with 3-liter sterilized water (the total volume of fermenter). The fermentation broth from the second round of fermentation was sampled at different timepoints to determine the CFU of yXF281 and total cells (yXF281 and yXF282). Viable titer of yXF281 was determined by using selective medium plates supplement with 1 mM OMeY, 2% (w/v) galactose, and G418 (200 μg/ml). See “Methods” for details. b Measurement of the CFU of yXF281 and its proportion in the population at different timepoints. The cyan bar represents the CFU/ml of yXF281 and dot connected by red line represents its proportion. The fermentation experiments were conducted in triplicate and the error bars represent the mean ± SEM of three biological replicates. Source data are provided as a Source Data file.