Kinetics of carbazole degradation by Pseudomonas putida in presence of sodium salicylate

The feasibility of a PAH- and phenol-degrading microorganism (Pseudomonas putida ATCC 17484) to degrade carbazole was investigated. While the culture could not utilize carbazole as a sole carbon and energy source, carbazole could be completely degraded in the presence of 200 mg/l sodium salicylate. It was found that there was a trace accumulation of autopolymerization products resulting from the degradation of sodium salicylate at the end of the experiments. Based on mass-spectrometric analysis, the identities of these products were proposed as a dimer of catechol and its derivative. Cell growth and degradation kinetics models were developed and experimentally validated over a wide range of concentrations of sodium salicylate (50–600 mg/l) and carbazole (0.5–4.5 mg/l). Cells grew on sodium salicylate based on Haldane kinetics with parameters of μm1=0.520 h−1, KS1=36.2 mg/l and KI1=1201.7 mg/l, while carbazole exerted toxicity inhibition to growth. When both carbazole and sodium salicylate were present, ATCC 17484 utilized them simultaneously but with lower specific rates. Model analysis indicates that carbazole inhibited sodium salicylate degradation more than the self-inhibition of sodium salicylate.