Metabolic profile analysis and kinetics of p-cresol biodegradation by an indigenous Pseudomonas citronellolis NS1 isolated from coke oven wastewater

Abstract

A p-cresol degrading bacterial strain was isolated from coke oven wastewater of an iron and steel plant industry. The isolated strain was identified as Pseudomonas citronellolis NS1 by 16S rRNA gene sequencing method. The isolated Pseudomonas species could degrade 1200 mg l−1 of p-cresol completely in 40 h. Further, at 1200 mg l−1 of initial p-cresol more than 95.4% TOC and 98.5% toxicity removal were also achieved by the microbial culture. The metabolic pathway of the Pseudomonas species was investigated using HPLC, UV visible spectra, FT-IR and GC–MS analysis. The major metabolic intermediate products identified in the bacterial culture were 4-methyl catechol, protocatechuic acid, 3-oxadipic acid, 4- carboxy muconolactone, 2-hydroxy muconicsemialdehyde and maleic acid. Based on the identified metabolic intermediate products, a tentative new meta-cleavage 3-oxoadipate pathway has been proposed. The biodegradation of p-cresol by the culture followed first order kinetic. The biokinetic parameters associated with biodegradation of p-cresol have been estimated as follow; μ = 0.353 h−1, Ksi = 464 mg l−1, Ks = 99.5 mg l−1. It was observed that, when the initial concentrations of p-cresol exceeded more than 1000 mg l−1, about 70% of the total substrate carbon was utilized towards microbial maintenance energy.