Fig. 4

Application of the CRISPRi system for enhancement of lysine production in DM1919, the l-lysine producer. Two different sgRNAs (gltA-r2 and gltA-r3) were expressed in DM1919 strain to repress gltA gene expression (note the details in Table 1 plasmids). The cell growth (closed symbol), glucose consumption (closed symbol), and l-lysine production (open symbol) were measured for the DM1919 strains (upper panel). Levels of mRNA expression of the gltA gene and the sigA gene as a control, and citrate synthase (CS) activity (μmol/min/mg of total protein) in the DM1919 strains were measured (lower panel). One unit (U) is defined as the amount of enzyme that converts 1 μmol of acetyl-coA to citrate per a minute at 30 °C. The l-lysine yields (mol/mol) were calculated (mole of l-lysine produced per mole glucose consumed). Data represents mean values of at least three cultivations and error bars represent standard deviations