Fig. 4

Comparison of the effect of CRISPRi-mediated multiplex gene repression on n-butanol production in E. coli. DH5α cells harboring pAB-HCTA and each pSECRi plasmid were grown in TB medium supplemented with 20 g/L glycerol and a 4 mM l-rhamnose or b various concentrations of l-rhamnose at 37 °C for 48 h. n-Butanol levels were determined by GC. The fold increase of n-butanol production was calculated as \({n{\text{-}}butanol}\; (fold) = \frac{{BtOH_{xv} }}{{BtOH_{null} }}\; \times \;100,\) where BtOH is n-butanol concentration. The subscript xv designates the tested cells harboring the pAB-HCTA and pSECRi plasmid in the presence of l-rhamnose, whereas null indicates a control with the same two plasmids in the absence of l-rhamnose. Data represent the averages of three biological cultures, and error bars show the standard deviation (SD)