Nicotiana tabacum -associated bioengineered Pseudomonas putida can enhance rhizoremediation of soil containing 2,4-dinit

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ORIGINAL ARTICLE

Nicotiana tabacum‑associated bioengineered Pseudomonas putida can enhance rhizoremediation of soil containing 2,4‑dinitrotoluene Özlem Akkaya1  Received: 27 April 2020 / Accepted: 12 August 2020 / Published online: 19 August 2020 © King Abdulaziz City for Science and Technology 2020

Abstract Rhizoremediation processes are based on plant-bacteria interactions and can be effectively used for cleaning many pollutants from the environment to overcome the constraints of individual phytoremediation. Here, 1 mM and 1.5 mM concentrations of 2,4-dinitrotoluene (2,4-DNT) degrading Pseudomonas putida (P. putida) strain KT.DNT and various growth stages of Nicotiana tabacum (N. tabacum) were initially assayed in in vitro tissue culture system and the best conditions for the association of plant-rhizobacterium were ascertained to remediation of the soil contaminated with 2,4-DNT. 5-days old N. tabacum plants inoculated with 2 × 106 cfu/mL bacterial inoculum for 3 weeks were preferred for rhizoremediation experiments as they showed a nearly threefold increase in the fresh and dry biomass in comparison to noninoculated ones. When these seedlings were planted either alone or together with P. putida KT2440 or P. putida KT.DNT in soils contaminated with 1 mM and 1.5 mM of 2,4-DNT, the maximum degradation rate of 98% and ~ 93% were determined at the end of 14 days by KT.DNT inoculated tobacco plants. Our results indicate that it would be advantageous to use the 2,4-DNT-degrading bacterium inoculated with N. tabacum plants to accelerate and enhance the cleanup of soil contaminated with 2,4-DNT. Keywords  2, 4-DNT degrading bacterium · Nicotiana tabacum · Plant-rhizobacteria interactions · Pseudomonas putida · Rhizoremediation

Introduction 2,4-DNT, is a typical soil contaminant at ammunition manufacturing sites, derived mainly from the synthesis of the explosive 2,4,6-trinitrotoluene (TNT) but also from the production of polyurethane foams and dyes (Nishino et al. 2000; Serrano-González et al. 2018). This mutagenic and carcinogenic substance is listed on the Hazardous Air Pollutants List ruled by the U.S. Environmental Protection Agency (EPA) (Lent et al. 2012; Xu and Jing 2012) and also on Resource Conservation and Recovery Act (RCRA) Toxicity Characteristic Leaching Procedure (TCLP) organics list. According to EPA (2006), soils and wastes that contain Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s1320​5-020-02395​-y) contains supplementary material, which is available to authorized users. * Özlem Akkaya [email protected] 1



Department of Molecular Biology and Genetics, Gebze Technical University, 41400 Kocaeli, Turkey

2,4-DNT are classified as RCRA characteristic hazardous waste and a special treatment will be needed, if they produce leachate comprising 2,4-DNT equal or above the TCLP threshold concentration (0.13 mg/L). The concentration of 2,4-DNT at firing points was determined above the detection limit (0.01 mg/kg (ppm)) and even higher at several propellant