Phenolic Precipitates from Soybean Peroxidase–Catalyzed Wastewater Treatment: Concentrated Waste Serves to Concentrate Its Progenitor

Abstract

The use of Triton X-100 (Triton) significantly improves enzyme economy for the removal of phenol from wastewater with crude soybean peroxidase (SBP, Enzyme Commission Number 1.11.1.7), a polymerization process that forms (poly) phenolic precipitates. The observation of SBP elution from phenolic precipitates in the presence of Triton was considered a competitive adsorption displacement phenomenon in order to explain the protection mechanism (Triton effect). Both SBP and Triton adsorption on the precipitates were characterized by Langmuir adsorption isotherms as single-adsorbate systems. As a binary-adsorbate system, the adsorption of Triton gradually reversed the adsorbed SBP back into the aqueous phase. The sigmoid elution curve was consistent with an orogenic displacement mechanism. A quantitative relationship between SBP elution as a function of Triton and precipitates concentrations was established by adapting the curves to a logistic function. The concept of using phenolic precipitates as an affinity matrix for concentrating SBP from dilute solution was proven and the feasibility of developing a related process was validated in both single-batch and consecutive cycles of operation. The process has the potential for producing low-cost enzyme concentrate, thereby enabling its application for industrial wastewater treatment.