APPLIED MICROBIAL AND CELL PHYSIOLOGY Roles of export genes cgmA and lysE for the production of L-arginine and L-citrulline by Corynebacterium glutamicum Dorit Lubitz 1 & João M. P. Jorge 1 & Fernando Pérez-García 1 & Hironori Taniguchi 1 & Volker F. Wendisch 1 Received: 4 May 2016 /Revised: 16 June 2016 /Accepted: 17 June 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract L-arginine is a semi-essential amino acid with ap- plication in cosmetic, pharmaceutical, and food industries. Metabolic engineering strategies have been applied for over- production of L-arginine by Corynebacterium glutamicum. LysE was the only known L-arginine exporter of this bacteri- um. However, an L-arginine-producing strain carrying a dele- tion of lysE still accumulated about 10 mM L-arginine in the growth medium. Overexpression of the putative putrescine and cadaverine export permease gene cgmA was shown to compensate for the lack of lysE with regard to L-arginine ex- port. Moreover, plasmid-borne overexpression of cgmA res- cued the toxic effect caused by feeding of the dipeptide Arg- Ala to lysE-deficient C. glutamicum and argO-deficient Escherichia coli strains. Deletion of the repressor gene cgmR improved L-arginine titers by 5 %. Production of L-lysine and L-citrulline was not affected by cgmA overexpression. Taken together, CgmA may function as an export system not only for the diamine putrescine and cadaverine but also for L-arginine. The major export system for L-lysine and L-arginine LysE may also play a role in L-citrulline export since production of L- citrulline was reduced when lysE was deleted and improved by 45 % when lysE was overproduced. Keywords Amino acid exporters . C. glutamicum . L-arginine . L-lysine . L-citrulline . CgmA . LysE . ArgO . E. coli Introduction The Gram-positive and generally recognized-as-safe, rod- shaped soil bacterium Corynebacterium glutamicum is an in- tensively studied organism that is currently used for the indus- trial production of the amino acids L-glutamate and L-lysine. The worldwide demand for these amino acids exceeds 5 mil- lion tons per year (Eggeling and Bott 2005; Kimura 2003; Wendisch 2014). C. glutamicum strains have been improved with respect to amino acid overproduction by a number of metabolic engineering strategies including the improvement of amino acid export. Though not intuitive, amino acid export may be essential under conditions of metabolic imbalance for amino acids that cannot be catabolized (Erdmann et al. 1993; Marin and Krämer 2007). C. glutamicum, for instance, can neither catabolize L-lysine nor L-arginine. Their biosynthesis is regulated at the enzyme and genetic levels so that intracel- lular accumulation of L-lysine and L-arginine due to uncon- trolled biosynthesis is very unlikely. However, excessive ac- cumulation of these amino acids may occur when growing on peptide substrates (Bellmann et al. 2001; Broer et al. 1993; Vrljic et al. 1996). Feeding dipeptides containing a readily catabolizable amino acid such as L-alanine and a non- catabolizable amino acid such as L-lysine led to a metabolic imbalance (Bellmann et al. 2001; Erdmann et al. 1993). Uptake and hydrolysis of dipeptides by C. glutamicum are fast and appear not to be regulated (Broer and Kramer 1991; Erdmann et al. 1993). Thus, under these conditions, accumu- lation of L-lysine was avoided by LysE-mediated export. LysE from C. glutamicum is known to export L-lysine and L-argi- nine (Bellmann et al. 2001; Vrljic et al. 1996). Feeding a dipeptide like Ala-Lys to a strain lacking LysE led to the intracellular accumulation of L-lysine to molar concentrations and growth of C. glutamicum ceased (Broer et al. 1993; Erdmann et al. 1993; Vrljic et al. 1996). Dorit Lubitz and João M. P. Jorge contributed equally to this work. * Volker F. Wendisch volker.wendisch@uni-bielefeld.de 1 Faculty of Biology and CeBiTec, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany Appl Microbiol Biotechnol DOI 10.1007/s00253-016-7695-1