Beyond amino acids: Use of the Corynebacterium glutamicum cell factory for the secretion of heterologous proteins.

The Gram-positive soil bacterium Corynebacterium glutamicum has a long tradition in industry as a potent cell factory for the production of various amino acids. Besides this, in the last few years it became increasingly clear that this microorganism can also efficiently be used as a host organism for the expression and secretion of biotechnologically or pharmaceutically relevant heterologous proteins. In this review, first a short overview is given on the two main protein export pathways (Sec and Tat) of C. glutamicum that can be exploited for the transport of heterologous target proteins across the cytoplasmic membrane. Subsequently, the current knowledge on the successful use of C. glutamicum for the secretory production of an already impressive variety of heterologous proteins derived from different pro- and eukaryotic sources is summarized, whereby a special emphasis is given on the various optimization strategies and tools that have recently been developed and that now can be used to establish and further improve C. glutamicum as a secretory expression platform for the production of any desired heterologous target protein.