Kinetics and Biodegredation Efficiency of Selected Bacteria Isolates on Pyrene and Chrysene

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental pollutants with significant toxicological and mutagenic effects, necessitating the exploration of efficient microbial biodegradation strategies for environmental remediation. This study evaluated the biodegradation efficiency and kinetics of selected bacterial isolates obtained from auto-mechanic workshop soils on pyrene and chrysene. Standard microbiological, molecular and biodegradation techniques were employed. Bacterial isolates were identified using 16S rRNA gene amplification and sequencing while biodegradation efficiency was assessed over a 25-day incubation period using pyrene and chrysene as sole carbon sources. Optical density measurements, degradation constants, half-life determination and specific growth rate analyses were used to assess biodegradation performance. Molecular characterization identified the isolates as Serratia marcescens strain SBZO4, Providencia rettgeri strain SBZO5, Proteus mirabilis strain SBZO9, Pseudomonas aeruginosa strain SBZ15 and Lysinibacillus sphaericus strain SBZ18. Optimum growth occurred at 30 °C and pH 7.5, with Providencia rettgeri recording the highest optical density value of 4.61 at pH 7.5. Complete degradation of pyrene and chrysene was achieved by Serratia marcescens and Lysinibacillus sphaericus within 15 to 20 days respectively. Pseudomonas aeruginosa exhibited high biodegradation constants of 0.2049 and 0.1599 for pyrene and chrysene, respectively. The shortest half-life values were observed using Serratia marcescens with 2.166 days for pyrene and 2.666 days for chrysene. These findings demonstrate the strong biodegradation potential of indigenous bacterial isolates for remediation of PAH-contaminated environments.