Biodegradation of 3-chlorobenzoic acid with electron shuttle systems: pathways and molecular identification

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ORIGINAL PAPER

Biodegradation of 3‑chlorobenzoic acid with electron shuttle systems: pathways and molecular identification Ola A. A. Khalil1 · Mohamed N. Abu el‑naga1 · Heba Abd‑Alla El‑Bialy1  Received: 15 November 2019 / Revised: 28 May 2020 / Accepted: 24 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract A synergy of biodegradation and electron shuttle systems is a promising strategy for eliminating pollutants including chlorinated aromatic compounds. The present work studies the degradation products of 3-chlorobenzoic acid by Pseudomonas putida in the presence of an electron shuttle system (ESS) composed of citrate and pyruvate as electron donors and the pollutant as an electron acceptor. Chromatographic results showed different pathways involved in the biodegradation process under the influence of electron shuttle systems. These routes depend on oxidation and reduction reactions for output byproducts to be easily mineralized by the bacterium under investigation. A nucleotide sequence with about 380 bp of a ton B gene was detected in P. putida and it resembles Escherichia coli Ton B. The relatedness tree of the selected gene reveals a high similarity and is comparable to P. aeruginosa (100%) and the highest variation with that of P. citronellolis (21.99%). Accordingly, in the presence of electron shuttle systems, the genes responsible for bacterial influx were activated to ease the biodegradation process. In an application model, the remediated-water samples were handled by two recycling processes using Scenedesmus obliquus and Trigonella foenum-graecum to evaluate the efficiency of this non-conventional treatment. In conclusion, this strategy succeeded in remediating the polluted water with chlorinated aromatic compounds for further applications. Keywords  3-chlorobenzoic acid · Biodegradation pathways · GC/MS · Pseudomonas putida · tonB gene · Electron shuttle system (ESS)

Introduction The chlorinated aromatic compounds family has been widely used in the manufacturing of dye intermediates, lubricants, pesticides, resin, solvents, and wood preservatives. They pose one of the most serious contemporary environmental problems owing to their toxicity to humans and wildlife, and relative persistence in aquatic sediments and soils Communicated by Erko Stackebrandt. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s0020​3-020-01965​-1) contains supplementary material, which is available to authorized users. * Heba Abd‑Alla El‑Bialy [email protected] 1



Radiation Microbiology Department, National Center for Radiation Research and Technology (NCRRT), Egyptian Atomic Energy Authority (EAEA), 3 Ahmed El‑Zumor street, B.O. 29, Children Village, Madinat Nasr, Cairo, Egypt

(Al-Limoun et al. 2018). Accordingly, researchers have paid attention to remediation processes to prevent the risks of cyclic aromatics on the surrounding ecosystems especially in developing countries that have unrestricted disposal regulations (Othman et al. 2011). Mi