Acid and Base Catalyzed Hydrolysis of Cyanophycin for the Biobased Production of Nitrogen Containing Chemicals

While growing on side-streams of the agro-industries, engineered microorganisms can produce ethanol and simultaneously bind L-aspartic acid and L-arginine in equimolar amounts in the polyamino acid cyanophycin. In this way, widely available amino acids can be isolated and utilized as an alternative feedstock for the production of nitrogen containing chemicals which are nowadays based on naphtha. The first step in the envisioned route from cyanophycin towards nitrogen containing chemicals is the complete or selective hydrolysis of cyanophycin. In this study, we investigated the acid and base catalyzed hydrolysis of cyanophycin. Acid catalyzed hydrolysis of cyanophycin yields both L-aspartic acid and L-arginine at comparable rates and is therefore suitable for complete hydrolysis. Upon base catalyzed hydrolysis, the rate of L-arginine liberation is overall significantly higher than that of L-aspartic acid, which enables selective hydrolysis of cyanophycin to yield a residue with commercially interesting polyaspartic acid functionality. To conclude this study, a cyanophycin residue with reduced L-arginine content was prepared and isolated.