Soybean peroxidase trapped in product precipitate during phenol polymerization retains activity and may be recycled

BACKGROUND: Studies with peroxidase (EC 1.11.1.7) have demonstrated that phenolic precipitate adsorbs free enzyme, inactivating it. The end-product inactivation model has been proposed to explain the effect. Additives, such as polyethylene glycol and Triton X-100, were reported to effectively extend enzyme lifetime by preventing the adsorption. RESULTS: It was found that soybean peroxidase (SBP, EC 1.11.1.7) trapped in precipitate during phenol polymerization retains activity. Contrary to the end-product inactivation model, recycling precipitate effectively utilized the active SBP. The minimum SBPconcentrationrequiredforthesubsequentbatchreactionremovalof1mmolL -1 phenolfromaqueoussolutionwasreduced from 1.2 to 0.5 U mL -1 . SBP adsorption on the precipitate was proven to be reversible by the addition of Triton X-100. Thus, a new explanation of SBP fate during the reaction is suggested: SBP is immobilized in situ in an active form with reduction of specific activity rather than inactivation. The adsorption is characterized by a Langmuir isotherm. CONCLUSIONS: The phenolic precipitate immobilizes SBP in an active form, consistent with the Langmuir isotherm model. Recycling the precipitate improves the enzyme economy in phenol removal. c � 2013 Society of Chemical Industry