Journal of Environmental Management 264 (2020) 110446 Available online 28 March 2020 0301-4797/© 2020 Elsevier Ltd. All rights reserved. Research article Enhancing hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX) remediation through water-dispersible Microbacterium esteraromaticum granules Sonal Yadav a , Abhishek Sharma b , Mohd Aamir Khan a , Ranju Sharma a , Mary Celin c , Anushree Malik a , Satyawati Sharma a, * a Centre for Rural Development and Technology, Indian Institute of Technology Delhi, Hauz Khas, Delhi, 110016, India b Amity Food and Agriculture Foundation, Amity University Uttar Pradesh, Noida, 201313, India c Centre for Fire, Explosives and Environment Safety, Defence Research & Development Organization, Min. of Defence, Brig. Mazumdar Road, Delhi, 110 054, India A R T I C L E INFO Keywords: RDX Aerobic biodegradation Water dispersible granules (WDG) M. esteraromaticum Formulation ABSTRACT In the current manuscript, we explored the remediation potential of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Gram-positive Microbacterium esteraromaticum 12849. The strain detoxifed 70.9 and 63.93% RDX in minimal nutrient medium and soil, respectively. Subsequently, the strain 12849 was formulated in form of water- dispersible granules (WDG) using talcum powder and alginic acid as inert ingredients. During the microcosm study, WDG exhibited 8.98% enhanced RDX degradation in contrast to the unformulated Microbacterium ester- aromaticum. The LC-MS analysis revealed the presence of two intermediates, namely N-methyl-N, N 0 -dini- tromethanediamine, and methylenedintramine, during the RDX degradation by strain 12849 in soil. Interestingly, no signifcant difference was observed in the rate of RDX degradation by strain 12849 due to the formulation process. The frst-order kinetics was seen in RDX degradation with a degradation coeffcient of 0.04 and 0.0339 day 1 by formulated and unformulated strain, respectively. The current investigation implies M. esteraromaticum as a potential microbe for RDX degradation and opens up the possibility of exploiting it in its effective WDG form for explosive contaminated sites. 1. Introduction Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is one of the noxious nitramine explosives soil contaminants at various military sites across the globe (Khan et al., 2015). It is a recalcitrant carcinogenic compound with moderate solubility in water, thereby posing as a grave concern for soils and groundwater environment (Card and Autenrieth, 1998). The traditional ways of remediating RDX through incineration or thermal decomposition, are expensive and result in the emission of harmful gases in the environment. Other emerging technologies like composting, though, have a short treatment time but are labor-intensive and costly (Kalderis et al., 2011). In this context, microbial remediation is now promoted as a more economical alternative that poses no threat to the environment (Jugnia et al., 2017). Various native microbial isolates viz., Proteobacterium (Al-Dhabaan and Bakhali, 2017), Rhodococcus sp. (Wilson and Cupples, 2016), Corynebacterineae sp. (Rylott et al., 2011) and Pseudomonas fuorescens (Roh et al., 2009) have been testifed against the RDX remediation. RDX can be degraded by microbes in aerobic as well as in anaerobic environments. Still, aerobic degradation is more advantageous as the rate of transformation of RDX is rapid due to enzymatic activities, and intermediates produced are relatively innocuous (Wang et al., 2017). The degradation occurs through the electron transfer which leads to sequential denitration initially converting RDX into MNX (hexahy- dro-1-nitroso-3,5-dinitro-1,3,5-triazine). It followed by ring cleavage and formation of intermediate products like 4-nitro-2,4-diazabutanal, methylenedinitramine etc. and fnally decomposing into nitrite, N 2 O, CO 2 and HCHO as the end-products (Hawari et al., 2000; Crocker et al., 2006; Fuller et al., 2016). Although there has been extensive research on xenobiotic microbial remediation and intricacies of degradation path- ways, the study has not been translated to on-feld success (in situ re- mediation’s). The paucity of technology that could immobilize the microbe and assist in degrading the pollutants regardless of the abiotic stress environment is one of the reasons behind that failure (Bjerketorp et al., 2018). The conversion of potent contaminant degraders into a stable formulation could be an engineered bioremediation strategy that * Corresponding author. Room no. 289, block III, India. E-mail addresses: satyawatis@hotmail.com, ssharma@rdat.iitd.ac.in (S. Sharma). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: http://www.elsevier.com/locate/jenvman https://doi.org/10.1016/j.jenvman.2020.110446 Received 26 November 2019; Received in revised form 21 February 2020; Accepted 15 March 2020