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Ecotoxicol Environ Saf. 2017 Apr;138:39-46. doi: 10.1016/j.ecoenv.2016.12.012. Epub 2016 Dec 22.

Enhancement of microbial 2,4,6-trinitrotoluene transformation with increased toxicity by exogenous nutrient amendment.

Author information

1
Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan.
2
Institute of Environmental Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan.
3
Department of Environmental Resources Management, Chia Nan University of Pharmacy & Science, Tainan, Taiwan.
4
Graduate School of Biotechnology and Bioengineering, Yuan Ze University, Chung-Li, Taiwan.
5
Department of Life Sciences, National Central University, Taoyuan, Taiwan.
6
Biodiversity Research Center, Academia Sinica, Taipei, Taiwan.
7
Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, Taiwan. Electronic address: cheng@nknu.edu.tw.

Abstract

In this study, the bacterial strain Citrobacter youngae strain E4 was isolated from 2,4,6-trinitrotoluene (TNT)-contaminated soil and used to assess the capacity of TNT transformation with/without exogenous nutrient amendments. C. youngae E4 poorly degraded TNT without an exogenous amino nitrogen source, whereas the addition of an amino nitrogen source considerably increased the efficacy of TNT transformation in a dose-dependent manner. The enhanced TNT transformation of C. youngae E4 was mediated by increased cell growth and up-regulation of TNT nitroreductases, including NemA, NfsA and NfsB. This result indicates that the increase in TNT transformation by C. youngae E4 via nitrogen nutrient stimulation is a cometabolism process. Consistently, TNT transformation was effectively enhanced when C. youngae E4 was subjected to a TNT-contaminated soil slurry in the presence of an exogenous amino nitrogen amendment. Thus, effective enhancement of TNT transformation via the coordinated inoculation of the nutrient-responsive C. youngae E4 and an exogenous nitrogen amendment might be applicable for the remediation of TNT-contaminated soil. Although the TNT transformation was significantly enhanced by C. youngae E4 in concert with biostimulation, the 96-h LC50 value of the TNT transformation product mixture on the aquatic invertebrate Tigriopus japonicas was higher than the LC50 value of TNT alone. Our results suggest that exogenous nutrient amendment can enhance microbial TNT transformation; however, additional detoxification processes may be needed due to the increased toxicity after reduced TNT transformation.

KEYWORDS:

2; 4; 6-trinitrotoluene (TNT); Bioremediation; Cometabolism; Nitroreductase; Toxicity; Transformation

PMID:
28006730
DOI:
10.1016/j.ecoenv.2016.12.012
[Indexed for MEDLINE]

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