What is Cyanophycin?

Cyanophycin (CGP) is a proteinogenic biopolymer of β-Asp-Arg dipeptides naturally produced by cyanobacteria, a gram-negative bacterium, earlier called “blue-green algae” which differs from all other bacteria by its oxygenic photosynthesis. CGP is composed of mainly arginine-aspartate dipeptides and is synthesised by a single enzyme, cyanophycin-synthetase (CphA), via non-ribosomal protein biosynthesis. Since the branched conformation of CGP differs substantially from the tertiary structure of proteins, CGP cannot be degraded by common proteases. Its degradation is restricted to a special class of enzymes, cyanophycinases, occurring exclusively in bacteria1. There, it serves as transient storage for nitrogen, carbon and energy2. CGP can be seen as a precursor for various applications in the chemical industry. It can replace polyacrylates and polyamide-based plastics3. It also can be applied for the production of food and feed supplements of high nutritional value4.

By introducing the cphA-gene from various bacteria CGP production has been already established in different bacteria, yeast and tobacco plants with yields up to 40%, 21% and 9.4% dry weight (dw), respectively. Nevertheless, the yeast-based cell culture systems are unsuitable for large-scale synthesis, since they are limited in terms of scalability, productivity and cost5, while tobacco cultivation can be easily upscaled using existing agricultural infrastructure and produce biomass in a cost-effecive, CO2 neutral way. The various CGP-molecules as have been produced from various plants and microorganisms, as such, have not been tested for their structural properties. These properties could be similar to polyaspartate. Thus, none of these were translated into an industrial production system or brought to market application so far. We will test the potential of CGP as biopolymer in individual applications but also in blends with other biopolymers such as starch, cellulose, PLA and PHA.

1 (Sallam and Steinbüchel 2011; Law et al 2009): Sallam A, Steinbüchel A. Biotechnological production of cyanophycin dipeptides. Patent US 8980845 B2. 2011 and Law AM, Lai SWS, Tavares J, Kimber MS. The Structural Basis of β-Peptide-Specific Cleavage by the Serine Protease Cyanophycinase. Journal of Molecular Biology 2009;392:393-404.

2 Ziegler et al (1998): Ziegler K, Diener A, Herpin C, Richter R, Deutzmann R, Lockau W. Molecular characterization of cyanophycin synthetase, the enzyme catalyzing the biosynthesis of the cyanobacterial reserve material multi- L-arginyl-poly- L-aspartate (cyanophycin). European Journal of Biochemistry 1998;54:154-159.

3 Börnke and Broer 2010; Mooibroek et al 2007: Börnke F, Broer I. Tailoring plant metabolism for the production of novel polymers and platform chemicals. Current Opinion in Plant Biology 2010;13:353-361; Mooibroek H, Oosterhuis N, Giuseppin M, Toonen M, Franssen H, Scott E, et al. Assessment of technological options and economical feasibility for cyanophycin biopolymer and high-value amino acid production. Applied Microbiology and Biotechnology 2007;77:257-267.

4 Sallam and Steichnuchel 2009, 2010; Santos et al 2012: Sallam A, Steinbuchel A. Cyanophycin-degrading bacteria in digestive tracts of mammals, birds and fish and consequences for possible applications of cyanophycin and its dipeptides in nutrition and therapy. J Appl Microbiol 2009;107:474-484.; Sallam A, Steinbuchel A. Dipeptides in nutrition and therapy: cyanophycin-derived dipeptides as natural alternatives and their biotechnological production. Appl Microbiol Biotechnol 2010;87:815-828; Santos S, Torcato I, Castanho MARB. Biomedical applications of dipeptides and tripeptides. Peptide Science 2012;98:288-293.

5 Ma JKC, Drake PMW, Christou P: The production of recombinant pharmaceutical proteins in plants. Nat Rev Genet 2003, 4:794-805. Merlin M, Gecchele E, Capaldi S, Pezzotti M, Avesani L: Comparative evaluation of recombinant protein production in different biofactories: The green perspective. BioMed Research International 2014, 2014. Sabalza M, Christou P, Capell T: Recombinant plant-derived pharmaceutical proteins: current technical and economic bottlenecks. Biotechnology Letters 2014, 36:2367-2379.