Carstens Lena, Cowan Andrew R, Seiwert Bettina, Schlosser Dietmar
Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
Institute for Environmental Microbiology and Biotechnology, University of Duisburg-Essen, Essen, Germany.
Front Microbiol. 2020 Feb 28;11:317. doi: 10.3389/fmicb.2020.00317. eCollection 2020.
Phthalate esters (PEs, Phthalates) are environmentally ubiquitous as a result of their extensive use as plasticizers and additives in diverse consumer products. Considerable concern relates to their reported xenoestrogenicity and consequently, microbial-based attenuation of environmental PE concentrations is of interest to combat harmful downstream effects. Fungal PE catabolism has received less attention than that by bacteria, and particularly fungi dwelling within aquatic environments remain largely overlooked in this respect. We have compared the biocatalytic and biosorptive removal rates of di--butyl phthalate (DBP) and diethyl phthalate (DEP), chosen to represent two environmentally prominent PEs of differing structure and hydrophobicity, by marine-, freshwater-, and terrestrial-derived fungal strains. Bisphenol A, both an extensively used plastic additive and prominent environmental xenoestrogen, was included as a reference compound due to its well-documented fungal degradation. Partial pathways of DBP metabolization by the ecophysiologically diverse asco- and basidiomycete strains tested were proposed with the help of UPLC-QTOF-MS analysis. Species specific biochemical reaction steps contributing to DBP metabolism were also observed. The involved reactions include initial cytochrome P450-dependent monohydroxylations of DBP with subsequent further oxidation of related metabolites, de-esterification via either hydrolytic cleavage or cytochrome P450-dependent oxidative -dealkylation, transesterification, and demethylation steps - finally yielding phthalic acid as a central intermediate in all pathways. Due to the involvement of ecophysiologically and phylogenetically diverse filamentous and yeast-like fungi native to marine, freshwater, and terrestrial habitats the results of this study outline an environmentally ubiquitous pathway for the biocatalytic breakdown of plastic additives. Beyond previous research into fungal PE metabolism which emphasizes hydrolytic de-esterification as the primary catabolic step, a prominent role of cytochrome P450 monooxygenase-catalyzed reactions is established.
邻苯二甲酸酯（PEs，邻苯二甲酸盐）由于在各种消费品中广泛用作增塑剂和添加剂，在环境中普遍存在。人们对其已报道的异雌激素性深感担忧，因此，基于微生物的环境中邻苯二甲酸酯浓度的衰减对于对抗有害的下游影响具有重要意义。与细菌相比，真菌对邻苯二甲酸酯的分解代谢受到的关注较少，特别是生活在水生环境中的真菌在这方面仍然基本被忽视。我们比较了海洋、淡水和陆地来源的真菌菌株对邻苯二甲酸二丁酯（DBP）和邻苯二甲酸二乙酯（DEP）的生物催化和生物吸附去除率，这两种物质被选来代表两种在环境中突出的结构和疏水性不同的邻苯二甲酸酯。双酚A作为一种广泛使用的塑料添加剂和突出的环境异雌激素，由于其真菌降解情况已有充分记录，被用作参考化合物。借助超高效液相色谱-四极杆飞行时间质谱（UPLC-QTOF-MS）分析，提出了受试的生态生理上不同的子囊菌和担子菌菌株对DBP代谢的部分途径。还观察到了对DBP代谢有贡献的物种特异性生化反应步骤。所涉及的反应包括DBP最初依赖细胞色素P450的单羟基化，随后相关代谢物的进一步氧化，通过水解裂解或依赖细胞色素P450的氧化脱烷基化进行的脱酯反应、酯交换反应和去甲基化步骤，最终在所有途径中产生邻苯二甲酸作为中心中间体。由于涉及来自海洋、淡水和陆地栖息地的生态生理和系统发育上不同的丝状和酵母样真菌，本研究结果概述了一种环境中普遍存在的塑料添加剂生物催化分解途径。除了先前强调水解脱酯作为主要分解代谢步骤的真菌邻苯二甲酸酯代谢研究之外，还确立了细胞色素P450单加氧酶催化反应的重要作用。
