Fig. 5.

Characterization of engineered sucrose-producing Synechocystis strains grown under continuous 50 μmol photons m⁻² s⁻¹ light. The strains S02 (over-expression of sucrose permease CscB and sucrose phosphate synthase SPS, and inactivation of glucosylglyserolphosphate synthase GGPS) and S02:Δflv3 (over-expression of CscB and SPS, and inactivation of GGPS and flavodiiron protein Flv3) were evaluated in respect to (a) sucrose production (mg l⁻¹), (b) growth (OD_750nm) and (c, d) gas flux rates. In a and b, the control strain S02 is shown in black and the strain S02:Δflv3 in red. In c and d, the lines represent the gross O₂ evolution (black), O₂ uptake (red), total carbon uptake (blue) and net O₂ evolution (magenta) measured on day 5 as a function of irradiance for the strains S02 and S02:Δflv3, respectively. The irradiance corresponding to the growth light intensity is highlighted in yellow. To assist the comparison between c and d, the zero gas flux level and the SO2 control strain total carbon uptake level at 500 μmol photons m⁻² s⁻¹ have been shown in horizontal dashed line and dotted line, respectively (see Additional file 1: Table S1 for calculated statistical comparison). The strains were cultivated in 1% CO₂ in the presence of 400 mM supplemented NaCl. In each case, the average and standard deviation were calculated from three to four independent experiments