Re-evaluation of cyanophycin synthesis in Corynebacterium glutamicum and incorporation of glutamic acid and lysine into the polymer
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Corynebacterium glutamicum was only examined in the early 2000s as a possible microorganism for the production of the polyamide cyanophycin (multi-l-arginyl-poly-[l-aspartic acid], CGP). CGP is a potential precursor for the synthesis of polyaspartic acid and CGP-derived dipeptides which may be of use in peptide-based clinical diets, as dietary supplements, or in livestock feeds. In the past, C. glutamicum was disregarded for CGP production due to low CGP contents and difficulties in isolating the polymer. However, considering recent advances in CGP research, the capabilities of this organism were revisited. In this study, several cyanophycin synthetases (CphA) as well as expression vectors and cultivation conditions were evaluated. The ability of C. glutamicum to incorporate additional amino acids such as lysine and glutamic acid was also examined. The strains C. glutamicum pVWEx1::cphAΔ1 and C. glutamicum pVWEx1::cphABP1 accumulated up to 14% of their dry weight CGP, including soluble CGP containing more than 40 mol% of the alternative side-chain amino acid lysine. The soluble, lysine-rich form of the polymer was not detected in C. glutamicum in previous studies. Additionally, an incorporation of up to 6 mol% of glutamic acid into the backbone of CGP synthesized by C. glutamicum pVWEx1::cphADh was detected. The strain accumulated up to 17% of its dry weight in soluble CGP. Although glutamic acid had previously been found to replace arginine in the side chain, this is the first time that glutamic acid was found to substitute aspartic acid in the backbone.
KeywordsCyanophycin Corynebacterium glutamicum Glutamic acid Lysine
We thank Cysal GmbH (Münster, Germany) for providing purified CphE.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain studies with human participants or animals performed by any of the authors.
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