Effects of secondary carbon supplement on biofilm-mediated biodegradation of naphthalene by mutated naphthalene 1, 2-dioxygenase encoded by Pseudomonas putida strain KD9.

Polycyclic aromatic hydrocarbons (PAHs) belong to a diverse group of environmental pollutants distributed ubiquitously in the environment. The carcinogenic properties of PAHs are the main causes of harm to human health. The green technology, biodegradation have become convenient options to address the environmental pollution. In this study, we analyzed the biodegradation potential of naphthalene with secondary carbon supplements (SCSs) in carbon deficient media (CSM) by Pseudomonas putida strain KD9 isolated from oil refinerary waste. The rigid-flexible molecular docking method revealed that the mutated naphthalene 1,2-dioxygenase had lower affinity for naphthalene than that found in wild type strain. Moreover, analytical methods (HPLC, qRT-PCR) and soft agar chemotaxis suggest sucrose (0.5 wt%) to be the best chemo-attractant and it unequivocally caused enhanced biodegradation of naphthalene (500 mg L-1 ) in both biofilm-mediated and shake-flask biodegradation methods. In addition, the morphological analysis detected from microscopy clearly showed KD9 to change its size and shape (rod to pointed) during biodegradation of naphthalene in CSM as sole source of carbon and energy. The forward versus side light scatter plot of the singlet cells obtained from flow cytometry suggests smaller cell size in CSM and lower florescence intensity of the total DNA content of cells. This study concludes that sucrose may be used as potential bio-stimulation agent.