Optimization of the biotransformation of L-tyrosine into L-dihydroxyphenylalanine (DOPA) by alginate-entrapped cells of Mucuna pruriens.

The optimization of the biotransformation of L-tyrosine into L-dihydroxyphenylalanine (DOPA), and of formyl-tyrosine into formyl-DOPA by alginate-entrapped cells of Mucuna pruriens is reported. This optimization is discussed in terms of parameters that are relevant for the entrapped cell system (charge of the beads with cells, bead diameter, permeation of the cells) and some parameters that are relevant for the enzymatic transformation (pH, pO2, concentration of ascorbate). The optimization experiments resulted in the description of a biotransformation system which operates at a constant redox potential. With this transformation system a transformation efficiency of 70% could be obtained, at a biotransformation-rate of 435 μmol·h(-1)·g(-1) (DW of cells) at a substrate concentration of 19 mM.