Abstract

Biodegradation ability of a native bacterial species Pelomonas aquatica strain WS2-R2A-65, isolated from nitramine explosive-contaminated effluent, for octogen (HMX) and hexogen (RDX) under aerobic condition has been explored in this study. Scanning electron microscopy indicated that the isolate WS2-R2A-65 retained its morphology both in the presence and absence of HMX or RDX. During an incubation period of 20 days, the isolate cometabolically degraded 78 and 86% of HMX and RDX with initial concentrations 6 and 60 mg L⁻¹, respectively. The degradation mechanism followed the first-order kinetics for both the nitramines with a 50% degradation time of 9.9 and 7.7 days for HMX and RDX, respectively. Positive electrospray ionisation mass spectroscopy indicates that biodegradation of nitamines follows multiple degradation pathways with one involving ring cleavage via single-electron transfer to nitramines leading to the elimination of single nitrite ion as evident from the formation of methylenedinitramine (MEDINA) and its methyl derivatives. The other pathways involve the reduction of both the nitramines to their nitroso, hydroxylamino and amino derivatives. These metabolites get further ring cleaved to give secondary metabolites viz. N-hydroxymethylmethylenedintramine, N-nitrosoamino and hydrazinyl derivatives leading to simpler less hazardous end products. Thus, the isolate WS2-R2A-65 proves to be an efficient microbial species for bioremediation of nitramines-contaminated effluent.

摘要

本研究探讨了在好氧条件下从硝胺爆炸物污染的污水中分离出的天然细菌物种水生佩罗单胞菌 WS2-R2A-65 对 octogen (HMX) 和 hexogen (RDX) 的生物降解能力。扫描电子显微镜表明分离物 WS2-R2A-65 在 HMX 或 RDX 存在和不存在的情况下均保持其形态。在 20 天的潜伏期中，分离物代谢降解了 78% 和 86% 的 HMX 和 RDX，初始浓度为 6 和 60 mg L ^-1， 分别。降解机制遵循硝胺的一级动力学，HMX 和 RDX 的 50% 降解时间分别为 9.9 天和 7.7 天。正电喷雾质谱表明，硝胺的生物降解遵循多种降解途径，其中一种涉及通过单电子转移到硝胺的环裂解，从而消除单个亚硝酸根离子，这从亚甲基硝胺 (MEDINA) 及其甲基衍生物的形成中可以看出。其他途径涉及将硝胺还原为它们的亚硝基、羟氨基和氨基衍生物。这些代谢物得到进一步的环裂解以产生次级代谢物，即。N-羟甲基亚甲基二胺，N-亚硝基氨基和肼基衍生物，导致更简单、危险性更低的最终产品。因此，分离物 WS2-R2A-65 被证明是一种有效的微生物物种，可用于生物修复被硝胺污染的废水。