Characterization of polycyclic aromatic hydrocarbon (PAH) degrading bacteria and optimization of physicochemical conditions for the production of catechol 1, 2-dioxygenase

Abstract

Biodegradation of recalcitrant polycyclic aromatic hydrocarbons (PAHs) is highly dependent on the activities of catabolic enzyme and the conditions for metabolism. The most significant studies on process optimization of conditions for catechol 1, 2 dioxygenase (C120) metabolism of PAHs used “one variable at a time” (OVAT) method, however, with its limitations. In this study, optimization of conditions for optimal C12O metabolism of PAH pollutants using the central composite design (CCD) of response surface methodology (RSM) was used. Enrichment technique using mineral salt medium (MSM) was used to isolate bacteria from oil-polluted water and soil milleu from Awoye community in Nigeria. Thereafter, the bacterial isolates were primarily screened through growth on mineral salt medium plates supplemented with (100 - 200) mM catechol and were subjected to secondary screening based on their initial catechol 1, 2-dioxygenase activity. Molecular tools were used to identify the isolate. Amongst the five (5) bacterial isolates acquired from primary screening, it was found that the cell free extract from isolate FEP B16a displayed the highest enzyme activity. Additionally, isolate FEP B16a was able to grow on MSM plate with 200 mM catechol. Based on CCD of RSM, the C12O produced from isolate FEP B16a had maximum activity at 35 ℃, pH 8.0, and 80μM of catechol. Molecular analysis confirmed it as a strain of Microbacterium hydrothermale FEP_B16a. This study concluded that CCD of RSM may be an efficient method to optimize C12O activity over the conventional approach of using single variable at a time.