Figure 7.

Phototrophic, high cell density cultivation of the best putrescine production strains obtained during the previous investigations in Figures 5 and 6 utilizing the CellDEG HD100 cultivators. (a) Picture of the HD100 cultivators and summary of the most important engineering strategies for increased putrescine accumulation. Overexpression of a high‐performance ODC enzyme was coupled with knockout of the native degrading enzyme AMX2 and optimized nutrient supply in a phototrophic cultivation. Improved substrate provisioning by arginase expression might have an effect in phototrophic conditions. (b) Detailed performance parameters of the putrescine production strains and incident light intensities. Cell concentrations, biomass dry weight (BDW), average residual nitrate and phosphate in the supernatant, as well as volumetric and specific putrescine yields and productivities are plotted. Error bars represent the standard deviation of biological triplicates. [Colour figure can be viewed at wileyonlinelibrary.com]