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Journal of Chemical Technology and Biotechnology, Volume 88, Issue 8, pages 1429–1435, August 2013.
Wei Feng,Keith E. Taylor, Nihar Biswas, Jatinder K. Bewtra .
Department of Civil and Environmental Engineering, University of Windsor, Windsor, ON, Canada &
Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
Abstract
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 SBP concentration required for the subsequent batch reaction removal of 1 mmol L-1 phenol from aqueous solution was reduced 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. © 2013 Society of Chemical Industry
© 2013 Society of Chemical Industry
Additional information:
Soybean peroxidase (SBP)-based treatment for the removal of selected aromatics in industrial wastewater is a cost-effective and easy-to-operate alternative to conventional processes. Compared with physical and chemical treatments, enzymes have high specificity for a target pollutant and result in a high efficiency of pollutant removal. The peroxidase-catalyzed oxidation effects polymerization of the substrate, rather than having pollutant transferred to a different phase (e.g., adsorption). It also has a lower risk of forming persistent intermediates and secondary pollutants when compared with advanced oxidation processes. Compared with biological treatments, enzyme treatment can deal with high concentrations of pollutant, has no shock loading effect, operates under mild conditions over a wide range of temperature, pH and salinity, has no lag-phase for biomass accumulation, is an easier process to control and maintain, is faster and, therefore, has a smaller footprint and has less sludge formation.
Instead of using additive (such as sacrificial polymer or surfactant) to maximize the enzyme efficiency, recycling precipitate, with active enzyme retained, could be a convenient alternative to save enzyme with no secondary contribution of organic carbon (Figure, below). The discovery of SBP and Triton X-100 interactions on phenolic precipitate was a major clue to explain the protective mechanism of non-ionic surfactant in enzymatic treatment. Study has continued in this direction. Besides explaining the mechanism, it has been extended to a process model, in which the raw SBP extract was concentrated by using phenolic precipitate as an affinity-matrix and Triton X-100 as an eluent.
