Development and Application of an Arabinose-Inducible Expression System by Facilitating Inducer Uptake in Corynebacterium glutamicum

Corynebacterium glutamicum is currently used for the industrial production of a variety of biological materials. Many available inducible expression systems in this species uselac -derived promoters fromEscherichia coli that exhibit much lower levels of inducible expression and leaky basal expression. We developed an arabinose-inducible expression system that contains thel -arabinose regulator AraC, thePBAD promoter from thearaBAD operon, and thel -arabinose transporter AraE, all of which are derived fromE. coli . The level of induciblePBAD -based expression could be modulated over a wide concentration range from 0.001 to 0.4%l -arabinose. This system tightly controlled the expression of the uracil phosphoribosyltransferase without leaky expression. When the gene encoding green fluorescent protein (GFP) was under the control ofPBAD promoter, flow cytometry analysis showed that GFP was expressed in a highly homogeneous profile throughout the cell population. In contrast to the case inE. coli ,PBAD induction was not significantly affected in the presence of different carbon sources inC. glutamicum , which makes it useful in fermentation applications. We used this system to regulate the expression of theodhI gene fromC. glutamicum , which encodes an inhibitor of α-oxoglutarate dehydrogenase, resulting in high levels of glutamate production (up to 13.7 mM) under biotin nonlimiting conditions. This system provides an efficient tool available for molecular biology and metabolic engineering ofC. glutamicum .