REACTION-ENGINEERING ANALYSIS OF L-LYSINE TRANSPORT BY CORYNEBACTERIUM-GLUTAMICUM

To identify potential L-lysine export limitations by Corynebacterium g lutamicum in the L-lysine production process, the excretion of L-lysin e was studied in continuous and fed-batch operated stirred tank reacto rs. A structured biochemical model of the L-lysine excretion mechanism was used to determine the activity of the export carrier and to calcu late a cell-specific concentration of the export carrier. for the bioc hemical characterization of this specific carrier concentration a stan dardized L-lysine efflux test was developed. Carrier activity, cell-sp ecific carrier concentration, and the specific L-lysine export rate we re identified as a function of pH value and L-lysine concentration in the reactors. Also, the correlation of these parameters to the metabol ic state of C. glutamicum was determined. The pH value in the reactor governs the carrier activity (maximum at pH 6.5) and the specific carr ier concentration (maximum at pH 8.0). The specific L-lysine export ra te, as the product of carrier activity and specific carrier concentrat ion, revealed a maximum at pH 7.0. Decreasing L-lysine productivities also correlated with decreasing specific carrier concentrations. Tile L-lysine concentration in the reactor had no effect on the specific ca rrier concentration but strongly inhibited the carrier activity. The s pecific export rate was reduced to 50% at 400 mM L-lysine compared to the specific export rate at 80 mM L-lysine. (C) 1996 John Wiley & Sons , Inc.