Bis(2-hydroxyethyl) terephthalate (BHET) is an important compound produced from poly(ethylene terephthalate) (PET) cleavage. It was selected as the representative substance for the study of PET degradation. A bacterial strain HY1 that could degrade BHET was isolated and identified as Enterobacter sp. The optimal temperature and pH for BHET biodegradation were determined to be 30°C and 8.0, respectively. The half-life of degradation was 70.20 h at an initial BHET concentration of 1,000 mg/L. The results of metabolites' analysis by liquid chromatograph-mass spectrometer revealed that BHET was first converted to mono-(2-hydroxyethyl) terephthalate (MHET) and then to terephthalic acid. Furthermore, an esterase-encoding gene, estB, was cloned from strain HY1, and the expressed enzyme EstB was characterized. The esterase has a molecular mass of approximately 25.13 kDa, with an isoelectric point of 4.68. Its optimal pH and temperature were pH 8.0 and 40°C, respectively. The analysis of the enzymatic products showed that EstB could hydrolyze one ester bond of BHET to MHET. To the best of authors' knowledge, this is the first report on the biodegradation characteristics of BHET by a member of the Enterobacter genus.

中文翻译：

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新分离的肠杆菌属对双（2-羟乙基）对苯二甲酸酯的生物降解。HY1及其酯酶特性的表征

对苯二甲酸双（2-羟乙基）酯 (BHET) 是一种重要的化合物，由聚对苯二甲酸乙二醇酯 (PET) 裂解产生。被选为PET降解研究的代表物质。分离出可降解 BHET 的细菌菌株 HY1 并鉴定为肠杆菌属。BHET 生物降解的最佳温度和 pH 值分别确定为 30°C 和 8.0。在 1,000 mg/L 的初始 BHET 浓度下，降解的半衰期为 70.20 小时。液相色谱-质谱仪对代谢物的分析结果表明，BHET 首先转化为对苯二甲酸单（2-羟乙基）酯（MHET），然后转化为对苯二甲酸。此外，从菌株HY1中克隆了酯酶编码基因estB，并对表达的酶EstB进行了表征。酯酶的分子量约为 25.13 kDa，等电点为 4.68。其最佳pH值和温度分别为pH 8.0和40°C。酶产物分析表明EstB可以将BHET的一个酯键水解为MHET。据作者所知，这是肠杆菌属成员关于 BHET 生物降解特性的第一份报告。