Acinetobacter species: Classification and cometabolism of chlorophenols

Sludge samples from activated sludge processes were evaluated for the occurrence of Acinetobacter species. Neural networks were applied to classify Acinetobacter genospecies based on their phenotypic characteristics. Acinetobacter species, particularly Acinetobacter johnsonii, were isolated consistently in significant numbers from different activated sludge processes. The ability of polyphosphate accumulation and poly-{dollar}beta{dollar}-hydroxybutyrate metabolism was shown to be widespread in the genus of Acinetobacter. Additionally, the inability of nitrate reduction among most Acinetobacter species indicates that Acinetobacter species play a significant role in biological phosphorous removal processes.; A competitive kinetic model of cometabolism with the energy constraint was developed and used to describe the cometabolism of 4- and 3-chlorophenols by phenol-induced cells of Acinetobacter species. The finite 4-chlorophenol transformation by resting cells of Acinetobacter was attributed solely to the depletion of reducing power. A variety of 4- or 3-chlorophenol degradation patterns (synchronous 4- or 3-chlorophenol degradation with the complete phenol utilization, incomplete degradation of 4- or 3-chlorophenol with the complete phenol utilization or incomplete degradation of both 3-chlorophenol and phenol) were shown to be a result of the higher affinity of chlorophenol than phenol and the initial ratio of phenol to either 4- or 3-chlorophenol. Different intermediate COD accumulation (1.26 mg COD/mg 4-chlorophenol vs 2.36 mg COD/mg 3-chlorophenol) and chloride release data (0.26 mg chloride/mg 4-chlorophenol vs. 0.13 mg chloride/mg 3-chlorophenol) implied that 4- and 3-catechols were the initial intermediary products, respectively, from 4- and 3-chlorophenol cometabolism. The toxicity effect of 3-chlorocatechols was alleviated by a higher initial concentration ratio of phenol to 3-chlorophenol.; The model predicted well these different degradation patterns of both growth and nongrowth substrates reported in literature. In the present study, the model is only able to predict the synchronous disappearance of phenol and 4-chlorophenol with the parameter values used, but the model was not able to predict the incomplete transformation of 4-chlorophenol. Nevertheless, the available energy necessary for cometabolism can be explicitly modeled due competition-dependent growth characteristics of growing cultures in the presence of both growth and nongrowth substrates.