Novel strategy for enhancing productivity in l-DOPA synthesis: The electroenzymatic approach using well-dispersed l-tyrosine

Although l-DOPA (l-3,4-dihydroxyphenylalanine) is widely used as a drug for Parkinson's disease, there are critical drawbacks in the commercial synthetic method such as low conversion rate, poor productivity, and long operational time. In order to overcome these limitations, a novel electroenzymatic system using tyrosinase/carbon nanopowder/polypyrrole composite as a working cathode was reported with the outstanding conversion rate up to 95.9%. However, the productivity was still limited due to a low solubility of the substrate l-tyrosine in aqueous phase. Herein, we demonstrated a novel strategy for enhancing the productivity by employing well-dispersed l-tyrosine as the substrate. When using well-dispersed l-tyrosine, not only the concentration of the substrate was increased to 90.6 gL−1 in aqueous phase but also the productivity was enhanced up to 15.3 gL−1 h−1. We also determined kinetic parameters in the electroenzymatic system and the kinetic results revealed that the outstanding conversion rate was based on the fast electrical reduction of the by-product to l-DOPA. Thus the electroenzymatic synthesis using well-dispersed l-tyrosine can be a potential candidate as a novel process for l-DOPA synthesis.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Well-dispersed l-tyrosine was prepared by wet-milling method and used as the substrate for l-DOPA synthesis in electroenzymatic system. ► Using well-dispersed l-tyrosine, we overcame solubility limitation in aqueous phase and the concentration was increased up to 500 mM. ► Consequently, the productivity was increased from 0.39 gL−1 h−1to 15.3 gL−1 h−1 in the electroenzymatic system for l-DOPA synthesis. ► Kinetic study and current response during the reaction revealed the reason for the outstanding conversion rate in the electroenzymatic system.