A coupled system involving arginase and urease for l-ornithine production

l -Ornithine, a non-protein amino acid, is widely used as a food supplement and nutrition product that is usually produced by the enzymatic hydrolysis of l -arginine. However, urea, a by-product, complicates purification of l -ornithine. Here, we describe a highly efficient coupled system, which involves Rummeliibacillus pycnus arginase and Jack bean urease, for the production of l -ornithine without urea residue. Although R. pycnus arginase exhibited the highest enzyme activity at pH 9.5 with Mn 2+ , it could be activated by Ni 2+ at 70   °C and pH 6.5. Kinetic study showed that, compared with Mn 2+ -containing arginase, Ni 2+ -containing arginase had a higher substrate affinity and catalysis efficiency. Based on the properties of commercial Jack bean urease and recombinant arginase, both enzymes showed robust activity at pH 6.5 and 40–50   °C. Using a coupled system involving arginase and urease for bioconversion, l -ornithine production of 37.8   g   l −1 was achieved with a 99.7% molar yield within 5   h. Thus, this coupled system represents an applicable strategy for the biosynthesis of l -ornithine.