Excretion of glutamate from Corynebacterium glutamicum triggered by amine surfactants

Corynebacterium glutamicum is used for the industrial production of glutamate. Excretion of the amino acid may be induced by various means. We have analyzed the characteristics of glutamate excretion induced by two amine surfactants, dodecylammonium acetate (DA) and dodecyltrimethylammonium bromide (DTA). Addition of these surfactants induced an immediate efflux of internal glutamate. It also induced a perturbation of the energetic parameters of the cell (decrease of delta mu H, decrease of the internal ATP concentration). The efflux was not the result of these perturbations: glutamate is taken up by the cells via an ATP-dependent unidirectional active transport system and no efflux took place as a consequence of an artificial decrease of the energetic parameters. In addition, amine surfactants also induced an excretion of other species, in particular potassium. We have tested the possibility that the effluxes result from a permeabilization of the lipid bilayer by analyzing the interactions between the surfactants and liposomes.