Catabolic enzyme activity and kinetics of pyrene degradation by novel bacterial strains isolated from contaminated soil

Polycyclic aromatic hydrocarbons (PAHs) with high molecular weight are difficult to degrade owing to their chemical structure and stability. This study reports degradation of pyrene by two potent Gram-positive bacterial strains isolated from petroleum-contaminated soil from Bijwasan supply location of Bharat Petroleum Corporation Limited (BPCL), India. The bacteria were identified as Kocuria flava and Rhodococcus pyridinivorans based on 16S rRNA gene sequencing. The degradation of pyrene, enzyme activity of Catechol 2,3-dioxygenase (C23O), dehydrogenase, and peroxidase, and the rate kinetics of degradation were investigated using the isolated bacteria. K. flava and R. pyridinivorans could degrade pyrene with an efficiency of 53.8% and 56.2%, within 15 days of incubation period under laboratory conditions. The consortium revealed 56.4% degradation of pyrene indicating that there is no significant synergistic/inhibitive effect. The activity (maximum on 9th day of incubation) of peroxidase enzyme (9.4 x 10(-4) and 16.9 x 10(-4) mu M/ml/min) was followed by dehydrogenase (2.6 x 10(-4) and 2.3 x 10(-4) mu M/ml/min) and C23O (2.2 x 10(-4) and 2.8 x 10(-4) mu M/ml/min) for K. flava and R. pyridinivorans, respectively, suggesting their involvement in ring-cleavage, diol-formation, and subsequent oxidation of the intermediates. Analysis of rate kinetics exhibited degradation of pyrene to be the first order reaction indicating that an increase in initial concentration of pyrene will not compromise with the ability of studied bacteria towards degradation. Analysis of initial and final concentration of treated media over HPLC confirmed significant pyrene degradation within 15 days. The study concludes that K. flava and R. pyridinivorans can play an active role in remediation of hydrocarbon-contaminated sites. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study demonstrated that the potent Gram-positive bacterial strains Kocuria flava and Rhodococcus pyridinivorans can efficiently degrade pyrene, with degradation rates of 53.8% and 56.2% within a 15-day incubation period under laboratory conditions. Enzyme activities and rate kinetics of degradation were also investigated, showing that these bacteria have the potential to play an active role in the remediation of hydrocarbon-contaminated sites. The study concluded that an increase in the initial concentration of pyrene will not compromise the bacteria's ability to degrade it, with no significant synergistic/inhibitive effects observed in the consortium.