Aerobic degradation of 2,4-dichlorophenoxyacetic acid and other chlorophenols by Pseudomonas strains indigenous to contaminated soil in South Africa: Growth kinetics and degradation pathway

• Published in: Applied biochemistry and microbiology Vol. 53; no. 2; pp. 209 - 216
• Main Authors: Olaniran, A. O., Singh, L., Kumar, A., Mokoena, P., Pillay, B.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.03.2017; Springer Nature B.V
• Subjects: Acids; Aerobic conditions; Biochemistry; Biomedical and Life Sciences; Bioremediation; Chlorophenol; Fluorescence; Growth kinetics; Kinetics; Life Sciences; Medical Microbiology; Microbiology; Pseudomonas; Pseudomonas fluorescens; Pseudomonas putida; Pseudomonas reactans; Soil contamination; South Africa; 2,4-dichlorophenol (2,4-DCP); spp; chlorophenols; 2,4,6-trichlorophenol (2,4,6-TCP); 2,4-dichlorophenoxyacetic acid (2,4-D)
• ISSN: 0003-6838; 1608-3024
• DOI: 10.1134/S0003683817020120

Three indigenous pseudomonads, Pseudomonas putida DLL-E4, Pseudomonas reactans and Pseudomonas fluorescens , were isolated from chlorophenol-contaminated soil samples collected from a sawmill located in Durban (South Africa). The obtained isolates were tested for their ability to degrade chlorophenolic compounds: 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in batch cultures. The isolates were found to effectively degrade up to 99.5, 98.4 and 94.0% with a degradation rate in the range of 0.67–0.99 (2,4-D), 0.57–0.93 (2,4-DCP) and 0.30–0.39 (2,4,6-TCP) mgL –1 day –1 for 2,4-D; 2,4-DCP and 2,4,6-TCP, respectively. The degradation kinetics model revealed that these organisms could tolerate up to 600 mg/L of 2,4-DCP. Catechol 2,3-dioxygenase activity detected in the crude cell lysates of P. putida DLL-E4 and P. reactans was 21.9- and 37.6-fold higher than catechol 1,2-dioxygenase activity assayed, suggesting a meta-pathway for chlorophenol degradation by these organisms. This is also supported by the generally high expression of C23O gene (involved in meta-pathway) relative to tfdC gene (involved in ortho-pathway) expression. Results of this study will be helpful in the exploitation of these organisms and/or their enzymes in bioremediation strategies for chlorophenol-polluted environment.