Developing a syngas fermentation process with Clostridium ljungdahlii for cyanophycin production

Cyanophycin is a biopolymer consisting of a poly aspartate chain with arginine that is bound to the side groups of the aspartate chain. The biosynthesis of cyanophycin requires only a single enzyme: cyanophycin synthetase (encoded by cphA). It was first discovered in cyanobacteria, and later, it was found that many other bacteria, including Clostridia, possess the genetic capability to produce cyanophycin. Cyanophycin has many potential applications, such as its use as bioplastic in medical approaches. This triggered the development of biotechnological production routes with cyanobacteria and Escherichia coli, both of which have certain limitations, such as difficult scalability as well as low quantity and/or quality of the biopolymer. This study aims to establish Clostridium ljungdahlii, which is a model microbe for syngas fermentation, as an alternative production platform via genetic engineering.

To achieve efficient cyanophycin production from syngas with C. ljungdahlii, several cyanophycin synthetases from various microbes will be investigated under different growth conditions. Additionally, metabolic engineering will be performed to enhance aspartate and arginine production from syngas. The resulting strains will be transferred to bioreactors, and the production process will be further optimized to achieve larger amounts of cyanophycin with high quality, subsequently enabling research to enhance the properties of the biopolymer for use in different applications. The planned strategies for the genetic modification of C. ljungdahlii and first results will be presented.