Growth kinetics of Pseudomonas aeruginosa RS1 on fluorene and dibenzothiophene, concomitant degradation kinetics and uptake mechanism

Abstract

The current study illustrates the growth kinetics of an efficient PAH and heterocyclic PAH degrading bacterial strain, Pseudomonas aeruginosa RS1 on fluorene (FLU) and dibenzothiophene (DBT) over the concentration 25–500 mg L⁻¹ and their concomitant degradation kinetics. The specific growth rate (µ) was found to lie within the range of 0.32–0.57 day⁻¹ for FLU and 0.24–0.45 day⁻¹ for DBT. The specific substrate utilization rate (q) of FLU and DBT over the log growth phase was between 0.01 and 0.14 mg FLU mg VSS⁻¹ day⁻¹ for FLU and between 0.01 and 0.18 mg DBT mg VSS⁻¹ day⁻¹ for DBT, respectively. The µ and q values varied within a narrow range for both FLU and DBT and they did not follow any specific trend. Dissolution together with direct interfacial uptake was the possible uptake mechanism for both FLU and DBT. The q values over the log growth phase depicts the specific substrate transformation rates. Kirby-Bauer disc diffusion studies performed using an E. coli strain indicated accumulation of some toxic intermediates of FLU and DBT during their degradation. Decrease in TOC and toxicity towards the end of the degradation experiments indicates further utilization of the intermediates.