L-arginine, an amino acid with a growing range of applications within the pharmaceutical, cosmetic, food, and agricultural industries, can be produced by microbial fermentation. Although it is the most nitrogen-rich amino acid, reports on the nitrogen supply for its fermentation are scarce. In this study, the nitrogen supply for the production of L-arginine by a genetically modified Escherichia coli strain was optimised in bioreactors. Different nitrogen sources were screened and ammonia

more »

... n, ammonium sulphate, ammonium phosphate dibasic, and ammonium chloride were the most favourable nitrogen sources for L-arginine synthesis. The key role of the C/N ratio for L-arginine production was demonstrated for the first time. The optimal C/N molar ratio to maximise L-arginine production while minimising nitrogen waste was found to be 6, yielding approximately 2.25 g/L of L-arginine from 15 g/L glucose with a productivity of around 0.11 g/L/h. Glucose and ammonium ion were simultaneously utilized, showing that this ratio provided a well-balanced equilibrium between carbon and nitrogen metabolisms.