Stabilized and Immobilized Bacillus subtilis Arginase for the Biobased Production of Nitrogen-Containing Chemicals

L-Ornithine could serve as an intermediate in the biobased production of 1,4-diaminobutane from L-arginine. Using the concept of biorefinery, L-arginine could become widely available from biomass waste streams via the nitrogen storage polypeptide cyanophycin. Selective hydrolysis of L-arginine to L-ornithine is difficult to perform chemically, therefore the stabilization and immobilization of Bacillus subtilis arginase (EC 3.5.3.1) was studied in a continuously stirred membrane reactor system. Initial pH of the substrate solution, addition of L-aspartic acid and reducing agents all appeared to have an effect on the operational stability of B. subtilis arginase. A remarkably good operational stability (total turnover number, TTN=1.13108) at the pH of arginine free base (pH 11.0) was observed, which was further improved with the addition of sodium dithionite to the substrate solution (TTN>1109). B. subtilis arginase was successfully immobilized on three commercially available epoxy-activated supports. Immobilization on Sepabeads EC-EP was most promising, resulting in a recovered activity of 75% and enhanced thermostability. In conclusion, the stabilization and immobilization of B. subtilis arginase has opened up possibilities for its application in the biobased production of nitrogen-containing chemicals as an alternative to the petrochemical productio