2.3. β-Galactosidase Assay

β-Galactosidase activity in C. glutamicum strains containing PldhA–lacZ fusion was determined as described previously [16]. Briefly, cells permeabilized with toluene were incubated with o-nitrophenyl-β-galactosidase in Z buffer (60 mM Na₂HPO₄, 40 mM NaH₂PO₄, 10 mM KCl, 1 mM MgSO4, 0.28% (v/v) β-mercaptoethanol, which was added on use) at 30 °C. The absorbance values at 420 and 550 nm were monitored to calculate activity in Miller units as previously described [34]. We confirmed that a strain carrying the vacant vector pCRA741 containing the promoter-less lacZ had no LacZ activity.