Optimization of process parameters for degradation of HMX with Bacillus toyonensis using response surface methodology

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Optimization of process parameters for degradation of HMX with Bacillus toyonensis using response surface methodology A. Meda1 · P. Sangwan2   · K. Bala1 Received: 9 September 2019 / Revised: 22 May 2020 / Accepted: 26 May 2020 © Islamic Azad University (IAU) 2020

Abstract Contamination of soil and water with explosive compounds like octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX or commonly known as high melting explosives) is increasing day by day due to their extensive use all over the world. High level of contamination has been found near military sites, explosive manufacturing facilities, war-lands, mines and exercise ranges. Remediation of such contaminants is necessary as they may have adverse impact on biotic as well as on abiotic environment. Present study was carried out with an objective to optimize the variable process parameters for the degradation of HMX in aqueous phase by indigenously isolated bacterial strain, Bacillus toyonensis from an actual HMX contaminated site in North India using response surface methodology. The relationship among varying initial concentrations of HMX, microbial inoculum size and degradation time was revealed in the current study. Results showed that 87.7% degradation was achieved at 2 mg/L initial HMX concentration with inoculum size of 4% on 15th day. High regression coefficient value (0.9878) further supported predictability of experimental data. Nitrite and nitrate concentrations estimated during the experiment indicate breakdown and degradation process of HMX. Findings of this study concluded that Bacillus toyonensis can be a potential microorganism to degrade HMX and can be used for microbial remediation of HMX contaminated sites. Keywords  Explosive · HMX · Bacillus toyonensis · Microbial remediation · Response surface methodology

Introduction Octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine (HMX, high melting explosive) is a heterocyclic nitramine, which is commonly used for military applications. It can enter the environment during the process of manufacturing, transport, usage and demilitarization. It is an important part of military applications and is classified as non-carcinogenic by US Environmental Protection agency (1998). However, Editorial responsibility: Jing Chen. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s1376​2-020-02783​-0) contains supplementary material, which is available to authorized users. * P. Sangwan [email protected] 1



Biofuels Research Laboratory, Discipline of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Indore, India



Centre for Fire, Explosive and Environment Safety, Defence Research and Development Organization, New Delhi, India

2

researchers revealed its toxicity effects on laboratory animals (Cuthbert et al. 1985; Greenhough and McDonald 1985). Further exposure of HMX in different mammalian species can cause convulsions, nausea and loss of consciousness (Wilson 1985). Many animal studies have indicated that