Cellular biocompatibility of cyanophycin substratum prepared with recombinant Escherichia coli

From the lab to the field and closer to the market: Production of the biopolymer cyanophycin in plants

A range of studies has investigated the production of biopolymers in plants but a comprehensive assessment of feasibility and environmental safety and consumer acceptance is lacking. This review delivers such an assessment. It describes the establishment of the production in tobacco and potato, the analysis of lead events in the greenhouse and in the field, the establishment and upscaling of effective isolation processes and storage conditions, taking the cyanobacterial storage peptide cyanophycin (CGP) as an example. The paper lists several industrial and medical applications of CGP and its building blocks Arg-Asp-dipeptides. This production is especially interesting because the CGP content can exceed 10 % of the dry weight (dw) in the greenhouse and still deliver 4 g per plant in the field. Furthermore, risk assessment of CGP production in potatoes in vitro, in vivo, in the greenhouse, and in the field showed no relevant differences concerning environment or consumer safety compared with the near isogenic control. A consumer choice analysis in four European countries showed a preference for biodegradable CGP in food-wrapping materials over conventional plastic wrapping. Although data on economic feasibility is lacking, CGP as a renewable, biodegradable and CO2-neutrally produced compound, is preferable over fossil fuels in many applications.

Cyanophycin modifications for applications in tissue scaffolding

Cyanophycin (CGP) is a polypeptide consisting of amino acids-aspartic acid in the backbone and arginine in the side chain. Owing to its resemblance to cell adhesive motifs in the body, it can be considered suitable for use in biomedical applications as a novel component to facilitate cell attachment and tissue regeneration. Although it has vast potential applications, starting with nutrition, through drug delivery and tissue engineering to the production of value-added chemicals and biomaterials, CGP has not been brought to the industry yet. To develop scaffolds using CGP powder produced by bacteria, its properties (e.g., biocompatibility, morphology, biodegradability, and mechanical strength) should be tailored in terms of the requirements of the targeted tissue. Crosslinking commonly stands for a primary modification method for renovating biomaterial features to these extents. Herein, we aimed to crosslink CGP for the first time and present a comparative study of different methods of CGP crosslinking including chemical, physical, and enzymatic methods by utilizing glutaraldehyde (GTA), UV exposure, genipin, 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS), and monoamine oxidase (MAO). Crosslinking efficacy varied among the samples crosslinked via the different crosslinking methods. All crosslinked CGP were non-cytotoxic to L929 cells, except for the groups with higher GTA concentrations. We conclude that CGP is a promising candidate for scaffolding purposes to be used as part of a composite with other biomaterials to maintain the integrity of scaffolds. The initiative study demonstrated the unknown characteristics of crosslinked CGP, even though its feasibility for biomedical applications should be confirmed by further examinations. KEY POINTS: • Cyanophycin was crosslinked by 5 different methods • Crosslinked cyanophycin is non-cytotoxic to L929 cells • Crosslinked cyanophycin is a promising new material for scaffolding purposes.

Recombinant Multi-l-Arginyl-Poly-l-Aspartate (Cyanophycin) as an Emerging Biomaterial

Multi-l-arginyl-poly-l-aspartate (MAPA) is a non-ribosomal polypeptide which synthesis is directed by cyanophycin synthetase, and its production can be achieved using recombinant microorganisms carrying the cphA gene. Along its poly-aspartate backbone, arginine or lysine links to each aspartate via an isopeptide bond. MAPA is a zwitterionic polyelectrolyte full of charged carboxylic, amine, and guanidino groups. In aqueous solution, MAPA exhibits dual thermal and pH responses similar to those stimuli-responsive polymers. Being biocompatible, the films containing MAPA can support cell proliferation and elicits minimal immune response in macrophages. Dipeptides from MAPA after enzymatic treatments can provide nutritional benefits. In light of the increasing interest in MAPA, this article focuses on the recent discovery of the function of cyanophycin synthetase and the potentials of MAPA as a biomaterial.

Cyanophycin Modifications-Widening the Application Potential

A circular bioeconomy approach is essential to slowing down the fearsome ongoing climate change. Replacing polymers derived from fossil fuels with biodegradable biobased polymers is one crucial part of this strategy. Cyanophycin is a polymer consisting of amino acids produced by cyanobacteria with many potential applications. It consists mainly of aspartic acid and arginine, however, its composition may be changed at the production stage depending on the conditions of the polymerization reaction, as well as the characteristics of the enzyme cyanophycin synthetase, which is the key enzyme of catalysis. Cyanophycin synthetases from many sources were expressed heterologously in bacteria, yeast and plants aiming at high yields of the polymer or at introducing different amino acids into the structure. Furthermore, cyanophycin can be modified at the post-production level by chemical and enzymatic methods. In addition, cyanophycin can be combined with other compounds to yield hybrid materials. Although cyanophycin is an attractive polymer for industry, its usage as a sole material remains so far limited. Finding new variants of cyanophycin may bring this polymer closer to real-world applications. This short review summarizes all modifications of cyanophycin and its variants that have been reported within the literature until now, additionally addressing their potential applications.

Applications of bacteria and their derived biomaterials for repair and tissue regeneration

Microorganisms such as bacteria and their derived biopolymers can be used in biomaterials and tissue regeneration. Various methods have been applied to regenerate damaged tissues, but using probiotics and biomaterials derived from bacteria with improved economic-production efficiency and highly applicable properties can be a new solution in tissue regeneration. Bacteria can synthesize numerous types of biopolymers. These biopolymers possess many desirable properties such as biocompatibility and biodegradability, making them good candidates for tissue regeneration. Here, we reviewed different types of bacterial-derived biopolymers and highlight their applications for tissue regeneration.

Characterization of an efficient extracellular cyanophycinase and its encoding cphEStrept. gene from Streptomyces pratensis strain YSM

Until now, no enzymes were described that hydrolyze cyanophycin granular protein (CGP) from a species of the genus Streptomyces. An isolate able to hydrolyze CGP was identified as Streptomyces pratensis strain YSM. The CGPase from S. pratensis strain YSM had an optimum activity at 42 °C and pH 8.5, and was able to degrade CGP at a rate of 12 ± 0.3 μg/mL min. Additionally, this CGPase hydrolyzes water-soluble CGP significantly faster than water-insoluble CGP. The molecular mass of CGPase subunits from S. pratensis strain YSM as determined by SDS-PAGE was about 43 kDa, and the enzyme was entirely inhibited by serine-protease inhibitors. The CGPase coding gene (cphE_Strept.) was amplified from genomic DNA using primers designed form consensus sequence of putative CGPase sequences. The cphE_Strept. was 1427 bp encoding a CGPase of 420 amino acids that showed about 44% and 22% similarities to CGPase from Pseudomonas anguilliseptica BI and Synechocystis sp. PCC 6803, respectively. The catalytic triad and serine-protease residues (GXSXG) were identified in the CphE_Strept. sequence. Dipeptides and tetrapeptides were identified as hydrolysis products. Biotechnological exploitation of S. pratensis strain YSM for CGPase production might have an advantage due to the reduction of separation costs and its ability to degrade CGP in phosphate buffer saline using actively growing or resting cells.

Microbial production of cyanophycin: From enzymes to biopolymers

Cyanophycin is an attractive biopolymer with chemical and material properties that are suitable for industrial applications in the fields of food, medicine, cosmetics, nutrition, and agriculture. For efficient production of cyanophycin, considerable efforts have been exerted to characterize cyanophycin synthetases (CphAs) and optimize fermentations and downstream processes. In this paper, we review the characteristics of diverse CphAs from cyanobacteria and non-cyanobacteria. Furthermore, strategies for cyanophycin production in microbial strains, including Escherichia coli, Pseudomonas putida, Ralstonia eutropha, Rhizopus oryzae, and Saccharomyces cerevisiae, heterologously expressing different cphA genes are reviewed. Additionally, chemical and material properties of cyanophycin and its derivatives produced through biological or chemical modifications are reviewed in the context of their industrial applications. Finally, future perspectives on microbial production of cyanophycin are provided to improve its cost-effectiveness.

Reversible Self-Assembly Nanovesicle of UCST Response Prepared with Multi-l-arginyl-poly-l-aspartate Conjugated with Polyethylene Glycol

Multi-L-arginyl-poly-L-aspartate (MAPA), also known as cyanophycin, containing a backbone of polyaspartate with arginine and lysine as side chains, was prepared with recombinant Escherichia coli. The insoluble part (iMAPA) was conjugated with polyethylene glycol (PEG) at two different levels, high (iMAPA(PEG)h) and low (iMAPA(PEG)l). Both levels of conjugation exhibited UCST (upper critical solution temperature)-type responses in the pH range of 3-10 at a concentration of 2 mg/mL. The cloud-point temperature of each conjugate also showed a positive correlation with concentration in PBS, falling between 20 to 58 °C at a concentration from 0.1 to 3 mg/mL. Hysteresis was observed to follow approximate paths under the same condition during repeated heating and cooling. Notably, the reversible formation of core-shell vesicles appeared at room temperature in PBS with a size of around 25 to 60 nm, as measured by DLS and observed under TEM. The reversibility was further employed to encapsulate doxorubicin (Dox) at different weight ratios of Dox to iMAPA(PEG)h. An encapsulation efficiency could reach as high as 70% with an equivalent loading capacity of 1.5 mg Dox/mg iMAPA(PEG)h. The Dox-loaded vesicles stayed stable at 4 °C for up to 4 weeks, with a minimal leakage below 2% and a slightly dilated morphology. Temperature-triggered release of Dox from the vesicles could be achieved by a step change of 5 °C successively from 37 to 62 °C in an effort to induce an initial 10% release at 37 °C gradually to complete release at 62 °C.