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Abstract

**Abstract**<br>

Cyanophycin (multi-<sc>l</sc>-arginyl-poly-<sc>l</sc>-aspartic acid; also known as cyanophycin grana peptide [CGP]) is a biopolymer that could be used in various fields, for example, as a potential precursor for the synthesis of polyaspartic acid or for the production of CGP-derived dipeptides. To extend the applications of this polymer, it is therefore of interest to synthesize CGP with different compositions. A recent re-evaluation of the CGP synthesis in<em>C. glutamicum</em>has shown that<em>C. glutamicum</em>is a potentially interesting microorganism for CGP synthesis with a high content of alternative amino acids. This study shows that the amount of alternative amino acids can be increased by using mutants of<em>C. glutamicum</em>with altered amino acid biosynthesis. With the DM1729 mutant, the lysine content in the polymer could be increased up to 33.5 mol%. Furthermore, an ornithine content of up to 12.6 mol% was achieved with ORN2(P<sub><em>gdh</em>4</sub>). How much water-soluble or insoluble CGP is synthesized is strongly related to the used cyanophycin synthetase. CphA<sub>Dh</sub>synthesizes soluble CGP exclusively. However, soluble CGP could also be isolated from cells expressing CphA<sub>6308</sub>Δ1 or CphA<sub>6308</sub>Δ1_C595S in addition to insoluble CGP in all examined strains. The point mutation in CphA<sub>6308</sub>Δ1_C595S partially resulted in a higher lysine content. In addition, the CGP content could be increased to 36% of the cell dry weight under optimizing growth conditions in<em>C. glutamicum</em>ATCC13032. All known alternative major amino acids for CGP synthesis (lysine, ornithine, citrulline, and glutamic acid) could be incorporated into CGP in<em>C. glutamicum</em>.

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