Degradation of dibutyl phthalate (DBP) by a bacterial consortium and characterization of two novel esterases capable of hydrolyzing PAEs sequentially
Degradation of dibutyl phthalate (DBP) by a bacterial consortium and characterization of two novel esterases capable of hydrolyzing PAEs sequentially
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细菌聚体对邻苯二甲酸二丁酯 (DBP) 的降解以及两种能够连续水解 PAE 的新型酯酶的表征
DOI：
10.1016/j.ecoenv.2020.110517
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发表时间：
2020-06-01
影响因子：
6.8
通讯作者：
Hong, Qing
中科院分区：
文献类型：
--
作者：
Lu, Meiyu;Jiang, Wankui;Hong, Qing
邻苯二甲酸酯（PAEs）是一类有毒的人为化合物，主要用作添加剂或增塑剂，其环境行为和降解机制引起了人们极大的关注和兴趣。在本研究中，通过富集法分离出一个由微杆菌属PAE - 1和潘多拉菌属PAE - 2组成的细菌群落，该群落可通过生化协同作用完全降解邻苯二甲酸二丁酯（DBP）。在菌株PAE - 1中，DBP通过两个连续的水解步骤经由邻苯二甲酸单丁酯（MBP）转化为邻苯二甲酸（PA），然后PA被菌株PAE - 2进一步降解。菌株PAE - 1能够水解许多邻苯二甲酸二烷基酯（PAEs），包括邻苯二甲酸二甲酯、二乙酯、二丁酯、二戊酯、苄基丁酯、二己酯、二（2 - 乙基己基）酯以及它们相应的邻苯二甲酸单烷基酯。通过鸟枪法从菌株PAE - 1中克隆出两个位于同一转录单元的酯酶基因dpeH和mpeH，并在大肠杆菌（DE3）中异源表达。DpeH对DBP的Km和kcat值分别为9.60 ± 0.97 μM和（2.72 ± 0.06）×10⁶ s⁻¹，而MpeH对MBP的Km和kcat值分别为18.61 ± 2.00 μM和（5.83 ± 1.00）×10⁵ s⁻¹。DpeH只能将邻苯二甲酸二烷基酯水解为相应的邻苯二甲酸单烷基酯，然后这些单烷基酯再由MpeH水解为PA。DpeH与微杆菌属MED - G48的一种α/β水解酶具有最高的相似性（53%），MpeH与来自须癣毛癣菌CBS 112371的一种分泌型脂肪酶仅有25%的同一性，这表明DpeH和MpeH是两种针对PAEs的新型水解酶。
Phthalate esters (PAEs), a class of toxic anthropogenic compounds, have been predominantly used as additives or plasticizers, and great concern and interests have been raised regarding its environmental behavior and degradation mechanism. In the present study, a bacterial consortium consisting of Microbacterium sp. PAE-1 and Pandoraea sp. PAE-2 was isolated by the enrichment method, which could degrade dibutyl phthalate (DBP) completely by biochemical cooperation. DBP was converted to phthalic acid (PA) via monobutyl phthalate (MBP) by two sequential hydrolysis steps in strain PAE-1, and then PA was further degraded by strain PAE-2. Strain PAE-1 could hydrolyze many dialkyl Phthalate esters (PAEs) including dimethyl, diethyl, dibutyl, dipentyl, benzyl butyl, dihexyl, di-(2-ethyhexyl) and their corresponding monoalkyl PAEs. Two esterase genes named dpeH and mpeH, located in the same transcription unit, were cloned from strain PAE-1 by the shotgun method and heterologously expressed in Escherichia. coli. (DE3). The Km and kcal values of DpeH for DBP were 9.60 +/- 0.97 mu M and (2.72 +/- 0.06) x 10(6) s(-1), while those of MpeH for MBP were 18.61 +/- 2.00 mu M and (5.83 +/- 1.00) x 10(5) s(-1), respectively. DpeH could only hydrolyze dialkyl PAEs to the corresponding monoalkyl PAEs, which were then hydrolyzed to PA by MpeH. DpeH shares the highest similarity (53%) with an alpha/beta hydrolase from Microbacterium sp. MED-G48 and MpeH shows only 25% identity with a secreted lipase from Trichophyton benhamiae CBS 112371, indicating that DpeH and MpeH are two novel hydrolases against PAEs.