Enhanced biodegradation of naphthalene by Pseudomonas sp. consortium immobilized in calcium alginate beads

Abstract Polycyclic aromatic hydrocarbons (PAHs) belong to a large group of organic pollutant which considers as a potential health hazard to living beings. Herein, naphthalene biodegradation potential by free and immobilized Pseudomonas putida strain KD10 and Pseudomonas sp. consortium were studied. Additionally, naphthalene 1, 2-dioxygenase ( nah Ac) was sequenced and analyzed, which reveals two altered amino acid residues. However, the altered amino acid residues are not present in the vicinity of the active site. The gas-phase binding free energy (ΔG London ) of the mutant variant of naphthalene 1, 2-dioxygenase was -7.10 kcal mol -1 which closely resembles the wild type variant. Naphthalene biodegradation rate by Pseudomonas putida strain KD10 was 79.12 mg L -1 day -1 and it was significantly elevated up to 123 mg L -1 day -1 by the immobilized Pseudomonas sp. consortium. The half-life ( t 1/2 ) for naphthalene biodegradation was 3.1 days with the inhibition constant ( k i ), substrate saturation constant ( k s ) and maximum specific degradation rate constant ( q max ) of 1268 mg L -1 , 395.5 mg L -1 and 0.65 h -1 , respectively, for the Pseudomonas putida strain KD10. However, the t 1/2 value was significantly reduced to 2 days along with k i , k s and q max values of 1475 mg L -1 , 298.8 mg L -1 and 0.71 h -1 , respectively, by the immobilized Pseudomonas sp. consortium. The GC-MS data suggest that KD10 might follow D-gluconic acid mediated meta-cleavage pathway of catechol biodegradation. It is concluded that naphthalene biodegradation performance by immobilized Pseudomonas sp. consortium was superior to free or immobilized Pseudomonas putida KD10. Microbial consortium immobilization could be a useful tool for water quality management and environmental remediation. Highlights Superior naphthalene biodegradation by Pseudomonas sp. consortium immobilized in calcium alginate beads. A common mutation prone amino acid stretch inside chain A of naphthalene 1, 2-dioxygenase has been identified. A new naphthalene biodegradation pathway by Pseudomonas putida strain KD10 has been proposed.