Tyrosinase immobilised on polyamide tubular membrane for the l-DOPA production: Total recycle and continuous reactor study

The production of l-3,4-dihydroxyphenylalanine (l-DOPA) from l-tyrosine catalysed from mushroom tyrosinase immobilised in a continuous membrane reactor was studied and compared with free enzyme used in a stirred tank reactor. The enzyme was immobilised by cross-flow filtration in asymmetric tubular membranes made of polyamide having nominal molecular weight cut off of 20 kDa. Results showed that the immobilization procedure did not alter the catalytic properties of the enzyme. The immobilised tyrosinase showed high stability over 30 h. In a continuous bioreactor the specific activity of tyrosinase is higher than that obtained with the free enzyme and those reported in the literature. The continuous operation minimizes the oxidation of the l-DOPA and for this reason the productivity (22.54 mg L-1 h-1) is 95% higher than that obtained with the total recycle reactor. Results obtained in the present study are promising for the development of the bioreactor at larger scale.