Screening of three commercial plant peroxidases for the removal of phenolic compounds in membrane bioreactors

A comparative study of three plant peroxidases, horseradish (HRP), soybean (SBP) and artichoke (AKPC), was carried out to select the most appropriate one for 4-chlorophenol treatment in an ultrafiltration membrane reactor. Soybean peroxidase showed the highest enzymatic activity, followed by HRP and AKPC. The same tendency was observed in a discontinuous tank reactor, where SBP attained more than 90% of 4-chlorophenol removal within the pH range tested. The optimum temperature was 30 degrees C, with SBP showing highest thermostability. With the ultrafiltration membrane reactor, SBP attained the highest operational stability, with 4-chlorophenol conversions of around 90% in the permeate stream for up to 200 minutes. Finally, permeate samples were analysed and no significant amount of enzyme was detected, so the observed loss of activity, less pronounced with SBP, was attributed to enzyme adsorption on the polymeric products deposited on the membrane surface. Soybean peroxidase was selected as the most appropriate peroxidase for future research.