Removal of phenol from water by membrane-immobilized enzymes: Part I. Dead-end filtration

A dead-end enzyme-immobilized membrane reactor was used to investigate the removal of catechol and phenol from water. A strain coded as AEK1, identified as a species of Pseudomonas syringae, was used to obtain the crude enzyme extract. Kinetic parameters of the native enzyme (apparent maximum reaction rate ( V m app ) and inhibition constant ( K i), based on catechol 1,2-dioxygenase activity) were determined experimentally as 0.31 μg/(ml s) and 19 μg/ml, respectively, by using the Lineweaver–Burk plot. The experimental reaction rates were in good agreement with the theoretical predictions based on Neufeld’s model. The maximum reaction rate occurred at pH 7.6 and 25 °C. Crude enzyme extract was totally immobilized onto a flat polyamide membrane with nominal pore size of 0.2 μm. The highest phenol degradation rate was 0.153 μg/(cm 2 s) when the initial concentration of phenol was 467 μg/ml at the flux rate of 9×10 −4 ml/(cm 2 s). Apparent reaction rate increased with increasing flux rate. The results obtained from enzyme-immobilized membrane reactor showed that the reaction rate was diffusion controlled. The stability of the immobilized enzyme was better than that of the free enzyme in solution and the immobilized enzyme kept 70% of its initial activity for approximately 100 h. The crude enzymatic extract in the free state was not able to degrade phenol as a result of extracellular nature of the enzyme. The technique provides a single-stage phenol removal process due to the production of linear chain metabolites or end products with the lowest energy levels.