Effect of pH and inoculum size on pentachlorophenol degradation by Pseudomonas sp

Pentachlorophenol (PCP) is a toxic compound which is used as a fungicide, bactericide, herbicide and chemical intermediate. Because of its toxicity, there is a need to decontaminate the PCP-laden soils and bioremediation is a very useful alternative to conventional clean-up methods. The success of this depends on finding strains able to degrade PCP in a changeable environment. The aim of this work was to study the influence of pH of the medium and the effect of inoculum size on pentachlorophenol degradation by Pseudomonas sp. A study of PCP degradation kinetics was performed to assess such effects. PCP was degraded rapidly at pH values from 6.3 to 8, but the maximum rate of PCP degradation by Pseudomonas sp. was at pH 6.3. In contrast, the PCP degradation kinetics at pH 5.5 were significantly lower, although PCP was totally depleted. These results show the broad range of pHs for PCP degradation for this strain. PCP was degraded at every inoculum size tested and PCP degradation increased with the increasing inoculum size, but cultures inoculated with the lowest inoculum showed the highest specific consumption rate. This reveals a lower consumption of PCP per CFU at a high population density. These results are useful to understand the physiological and biochemical properties of Pseudomonas sp. before its optimum use in environmental application and these data will assist in choosing the right PCP-degrader for a changeable environment.