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Biodegradation of phthalic acid esters (PAEs) by Cupriavidus oxalaticus strain E3 isolated from sediment and characterization of monoester hydrolases
Chemosphere ( IF 8.8 ) Pub Date : 2020-12-04 , DOI: 10.1016/j.chemosphere.2020.129061
Fangyuan Chen , Xuli Li , Yiqie Dong , Jiahao Li , Yixin Li , He Li , Lei Chen , Min Zhou , Haobo Hou

Phthalic acid esters (PAEs) are teratogenic and carcinogenic and mainly metabolized by microorganisms in sediment. A novel strain, Cupriavidus oxalaticus strain E3, was isolated and characterized from sediment for PAEs degradation. The transformation of dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) as the sole carbon source by strain E3 was systematically studied in the darkness through the kinetic studies and analysis of intermediates. After the initial lag pause of 5 h–8 h, the strain efficiently degraded 87.4%–94.4% of DBP and 82.5%–85.6% of DEHP at an initial amount of each phthalate of 200 mg/L after 60 h of incubation. The biodegradation rate of DBP and DEHP followed a first-order kinetic model, and degradation rate constants (k) of them by E3 were 1.37 and 0.86 d−1, respectively. Gas chromatography–mass spectrometry (GC–MS) results revealed that the tentative PAEs degradation pathway, included the transformation from PAEs to phthalic acid (PA) and the complete mineralization of PA. In the phase of PAEs to PA, DBP with short sides reduced the chain length via hydrolyzation, and DEHP with long sides reduced the chain length via hydrolyzation and β-oxidation. The 3D model of monoester hydrolase from C. oxalaticus was predicted and used for docking with mono-2-ethylhexyl phthalate (MEHP) and mono-n-butyl phthalate (MBP). The docking results showed that the conserved catalytic triplet structure (Ser140, His284, and Asp254) acted as active sites and participated in degrading PMEs. This study provided novel insights into the mechanisms of PAEs degradation at a molecular level and widened the scope of functional bacteria by isolating strain E3.



中文翻译:

从沉淀物中分离的草酸铜尿杆菌E3菌株对邻苯二甲酸酯(PAEs)的生物降解及单酯水解酶的表征

邻苯二甲酸酯(PAE)具有致畸性和致癌性,主要由沉积物中的微生物代谢。分离出一种新菌株草酸铜尿杆菌E3株,并从沉积物中表征PAEs的降解。通过动力学研究和中间体分析,系统地研究了菌株E3对邻苯二甲酸二丁酯(DBP)和邻苯二甲酸双(2-乙基己基)酯(DEHP)作为唯一碳源的转化。经过最初的5 h–8 h的延迟停顿后,在孵育60 h后,以200 mg / L的邻苯二甲酸酯的初始量,菌株有效降解了87.4%–94.4%的DBP和82.5%–85.6%的DEHP。DBP和DEHP的生物降解率遵循一阶动力学模型,E3​​对它们的降解率常数(k)分别为1.37和0.86 d -1, 分别。气相色谱-质谱(GC-MS)结果表明,暂定的PAE降解途径包括从PAE到邻苯二甲酸(PA)的转化以及PA的完全矿化。在PAE到PA的阶段,短边的DBP通过水解减少了链长,长边的DEHP通过水解和β-氧化减少了链长。草酸胞菌单酯水解酶的3D模型被预测并用于与邻苯二甲酸单-2-乙基己酯(MEHP)和邻苯二甲酸单正丁酯(MBP)对接。对接结果表明,保守的催化三联体结构(Ser140,His284和Asp254)充当活性位点并参与降解PME。这项研究提供了分子水平上PAEs降解机理的新见解,并通过分离菌株E3扩大了功能性细菌的范围。

更新日期:2020-12-10
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