Kinetics of phenol biotransformation

Abstract

Phenol and its homologues are aromatics containing hydroxyl, methyl, amide and sulphonic groups attached to the benzenoid molecules. These molecules are, both, anthropogenic and xenobiotics. Phenols are environmental pollutants discharged through wastewaters from fossil fuel refining processes, phenol manufacturing plants, pharmaceutical and a variety of other industries. Phenols are toxic to several biochemical reactions. However, biological transformation of phenols to non-toxic entities exists in specialized microbes, having enzymes of aromatic catabolic pathways. Transformation of phenols is also inhibited by the presence of other toxic materials such as cyanides and sulphides that are present in the industrial wastes having phenols as the dominant carbonaceous material. Kinetics of the biotransformation of phenols using pure cultures isolated in the laboratory, mixture of a consortium of the pooled cultures and enriched activated sludge biomass in pure substrates, mixed substrates and actual phenolic waste has been estimated under varying input concentrations. Experimental results from these studies have been subjected to analysis by mathematical models using Monod's and Haldane's equations to test the validity of these models in interpreting the data on inhibitory substances under steady as well as unsteady state operations of wastewater treatment plants. Comparative evaluation of the kinetic parameters reveals that Monod's model can be employed for the estimation of the kinetic constant μ only while Haldane's model has to be used for the calculation of μ max and K 1.