Polyurethanes (PU) are the sixth most produced plastics with around 18-million tons in 2016, but since they are not recyclable, they are burned or landfilled, generating damage to human health and ecosystems. To elucidate the mechanisms that landfill microbial communities perform to attack recalcitrant PU plastics, we studied the degradative activity of a mixed microbial culture, selected from a municipal landfill by its capability to grow in a water PU dispersion (WPUD) as the only carbon source, as a model for the BP8 landfill microbial community. The WPUD contains a polyether-polyurethane-acrylate (PE-PU-A) copolymer and xenobiotic additives (N-methylpyrrolidone, isopropanol and glycol ethers). To identify the changes that the BP8 microbial community culture generates to the WPUD additives and copolymer, we performed chemical and physical analyses of the biodegradation process during 25 days of cultivation. These analyses included Nuclear magnetic resonance, Fourier transform infrared spectroscopy, Thermogravimetry, Differential scanning calorimetry, Gel permeation chromatography, and Gas chromatography coupled to mass spectrometry techniques. Moreover, for revealing the BP8 community structure and its genetically encoded potential biodegradative capability we also performed a proximity ligation-based metagenomic analysis. The additives present in the WPUD were consumed early whereas the copolymer was cleaved throughout the 25-days of incubation. The analysis of the biodegradation process and the identified biodegradation products showed that BP8 cleaves esters, C-C, and the recalcitrant aromatic urethanes and ether groups by hydrolytic and oxidative mechanisms, both in the soft and the hard segments of the copolymer. The proximity ligation-based metagenomic analysis allowed the reconstruction of five genomes, three of them from novel species. In the metagenome, genes encoding known enzymes, and putative enzymes and metabolic pathways accounting for the biodegradative activity of the BP8 community over the additives and PE-PU-A copolymer were identified. This is the first study revealing the genetically encoded potential biodegradative capability of a microbial community selected from a landfill, that thrives within a WPUD system and shows potential for bioremediation of polyurethane- and xenobiotic additives-contamitated sites.

中文翻译：

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选定的垃圾填埋场微生物群落对顽固性聚氨酯和外源添加剂的降解及其基于邻近连接的宏基因组分析揭示的生物降解潜力。

聚氨酯 (PU) 是第六大产量塑料，2016 年产量约为 1800 万吨，但由于它们不可回收，因此被焚烧或填埋，对人类健康和生态系统造成损害。为了阐明垃圾填埋场微生物群落攻击顽固性 PU 塑料的机制，我们研究了混合微生物培养物的降解活性，该混合微生物培养物是从市政垃圾填埋场中选择的，因其能够在水性 PU 分散体 (WPUD) 作为唯一碳源中生长，作为 BP8 垃圾填埋场微生物群落的模型。WPUD 含有聚醚-聚氨酯-丙烯酸酯 (PE-PU-A) 共聚物和外源添加剂（N-甲基吡咯烷酮、异丙醇和乙二醇醚）。为了确定 BP8 微生物群落培养物对 WPUD 添加剂和共聚物产生的变化，我们对培养 25 天期间的生物降解过程进行了化学和物理分析。这些分析包括核磁共振、傅里叶变换红外光谱、热重分析、差示扫描量热法、凝胶渗透色谱以及与质谱技术相结合的气相色谱。此外，为了揭示 BP8 群落结构及其基因编码的潜在生物降解能力，我们还进行了基于邻近连接的宏基因组分析。WPUD 中的添加剂很早就被消耗掉，而共聚物则在 25 天的孵化过程中被裂解。对生物降解过程和鉴定的生物降解产物的分析表明，BP8 在共聚物的软链段和硬链段中通过水解和氧化机制裂解酯、CC 以及顽固的芳香族氨基甲酸酯和醚基团。基于邻近连接的宏基因组分析允许重建五个基因组，其中三个来自新物种。在宏基因组中，鉴定了编码已知酶的基因，以及解释 BP8 群落对添加剂和 PE-PU-A 共聚物的生物降解活性的推定酶和代谢途径。这是第一项揭示从垃圾填埋场中选出的微生物群落的基因编码潜在生物降解能力的研究，该微生物群落在 WPUD 系统中繁衍生息，并显示出对聚氨酯和外源添加剂污染场地进行生物修复的潜力。