FIG 3 .
Detection of high levels of l-Glu in supernatants from overnight cultures of E. coli strain WM335 expressing DapFCT grown with exogenous d-Glu. (a) Racemase activity was measured via a coupled biochemical reaction, i.e., the racemization of glutamate, followed by the dehydrogenation of l-Glu to α-ketoglutarate and ammonia. (b) Cultures of WM335 and WM335/pBAD18::dapFCT were grown overnight in the presence of arabinose and exogenous d-glutamate. Supernatants were measured for the presence of l-Glu by utilizing LGDH as described in Materials and Methods. Growth medium (Luria broth) supplemented with l- or d-Glu was used for a positive or negative control (red triangles and orange diamonds, respectively). Symbols represent mean values of two independent biological replicates, and error bars represent ranges.