Polyphenols represent a wide class of organic compounds characterised by oxidrylic group bound to an aromatic ring. Their presence makes agro-food wastewaters phytotoxic and not Suitable to conventional biological oxidation because of the inhibition of the bacterial activity. In this work the oxidation of polyphenols has been achieved by means of an enzymatic reaction carried out in a membrane bioreactor where the enzyme has been confined upstream the membrane. Tyrosinase from mushroom has been used as biocatalyst confined in a flat membrane bioreactor: an experimental study has been carried out in order to select the optimal operating conditions and a theoretical analysis has been also carried out in order to design the optimal bioreactor configuration for the process scale-up. The kinetic of the enzymatic oxidation has been preliminarily Studied to establish the reaction pattern. A transport model has been also formulated to characterize the behaviour of the enzyme membrane reactor. The bioreactor configuration and its performance have been analysed in order to optimize the process conversion. The results of the experimental analysis in terms of products distribution confirmed the validity of the enzyme membrane bioreactor for the oxidation of polyphenols.