Degradation of dimethyl terephthalate ester and its isomer by mangrove microoganisms

Abstract

Five morphologically distinct bacteria isolated from mangrove sediment by enrichment culture, were identified and tested for their ability to degrade dimethyl terephthalate （DMT） and its isomer dimethyl isophthalate (DMI). DMT at a concentration of 98 mg/L was degraded completely within 36 days at an initial pH 7.0，and two intermediates were identified as monomethyl terephthalate and terephthalic acid. DMI at a concentration of 220 mg/L was degraded within 35 days by a mixed culture, but one of the intermediates was identified as monomethyl isophthalate and accumulated in the culture. Based on the chemical structures of intermediates identified, the possible metabolic pathway of DMT was proposed as: DMT→MMT→TA →CO2+ H2O. Our results suggested that DMT be easier to be degraded than DMI. Fig 6, Tab 2, Ref 18

从红树林底泥中以对苯二甲酸二甲酯和间苯二甲酸二甲酯为碳和能源通过富集培养分离到５株细菌，并对其进行了鉴定，分别是Pasteurella multocida SDMTa (多杀巴斯德氏菌)、Klebsiella oxytoca SDMTb (产酸克雷伯氏菌)、Klebsiella sp. SDMTc (克雷伯氏菌株)、Sphingomonas paucimobilis SDMIy (少动鞘氨醇单胞菌)和Methylobacterium mesophilicum SDMIr (嗜中温甲基杆菌).这些微生物对对苯二甲酸二甲酯及其异构体间苯二甲酸二甲酯有较强的降解能力.在pH为7的条件下，浓度为98 mg/L的对苯二甲酸二甲酯（DMT）可在36 d内被完全降解，主要中间产物为对苯二甲酸一甲酯（MMT）和对苯二甲酸（TA）.在混合培养条件下，浓度达220 mg/L的间苯二甲酸二甲酯在35 d内降解达99％以上，但其中间产物间苯二甲酸一甲酯（MMI）不能被降解而在培养液中积累.根据鉴定出的中间产物，对苯二甲酸二甲酯的生化降解途径为：DMT→MMT→TA→CO2 + H2O.研究结果表明，对苯二甲酸二甲酯的2个酯基的水解是决定其完全矿化的重要起始步骤.对苯二甲酸二甲酯比间苯二甲酸二甲酯更容易被降解. 图6 表2 参18