Department of Microbiology, Universidade Federal de Viçosa (UFV), Viçosa, MG, Brazil.
Department of Chemistry, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.
Environ Pollut. 2023 Sep 15;333:122016. doi: 10.1016/j.envpol.2023.122016. Epub 2023 Jun 18.
Polyurethanes (PUs) are found in many everyday products and their disposal leads to environmental accumulation. Therefore, there is an urgent need to develop ecologically sustainable techniques to biodegrade and recycle this recalcitrant polymer and replace traditional methods that form harmful by-products. Serratia liquefaciens L135 secretes a polyurethanase with lipase activity, and this study explores the biodegradation of PUs by this bacterium and its enzyme through in silico and in vitro analyses. PUs monomers and tetramers were constructed in silico and tested with modeled and validated structure of the polyurethanase from S. liquefaciens. The molecular docking showed that all PUs monomers presented favorable interactions with polyurethanase (values of binding energy between -84.75 and -121.71 kcal mol), including PU poly[4,4'-methylenebis (phenyl isocyanate)-alt-1,4-butanediol/di (propylene glycol)/polycaprolactone] (PCLMDI). Due to repulsive steric interactions, tetramers showed less favorable interactions (values between 24.26 and -45.50 kcal mol). In vitro analyses evaluated the biodegradation of PUs: Impranil® and PCLMDI; this latter showed high binding energy with this polyurethanase in silico. The biodegradation of Impranil® by S. liquefaciens and its partially purified polyurethanase was confirmed in agar by forming a transparent halo. Impranil® disks inoculated with S. liquefaciens and incubated at 30 °C for six days showed rupture of the PU structure, possibly due to the formation of cracks visualized by scanning electron microscopy (SEM). PCLMDI films were also biodegraded by S. liquefaciens after 60 days of incubation, with the formation of pores and cracks visualized by SEM. The biodegradation may have occurred due to the action of polyurethanase produced by this bacterium. This work provides essential information on the potential of S. liquefaciens to biodegrade PUs through in silico analyses combined with in vitro analyses.
聚氨酯（PUs）存在于许多日常产品中，其处置会导致环境积累。因此，迫切需要开发生态可持续的技术来生物降解和回收这种难降解的聚合物，并取代形成有害副产物的传统方法。液化沙雷氏菌 L135 分泌一种具有脂肪酶活性的聚氨酯酶，本研究通过计算机模拟和体外分析探索了该细菌及其酶对 PUs 的生物降解。通过计算机模拟构建了 PUs 单体和四聚体，并使用液化沙雷氏菌的聚氨酯酶的建模和验证结构进行了测试。分子对接表明，所有 PUs 单体都与聚氨酯酶表现出有利的相互作用（结合能值在-84.75 到-121.71 kcal/mol 之间），包括 PU 聚[4,4'-亚甲基双（苯基异氰酸酯）-alt-1,4-丁二醇/二（丙二醇）/聚己内酯]（PCLMDI）。由于排斥的空间相互作用，四聚体表现出不太有利的相互作用（值在 24.26 到-45.50 kcal/mol 之间）。体外分析评估了 PUs 的生物降解：Impranil®和 PCLMDI；后者在计算机模拟中与这种聚氨酯酶表现出高结合能。液化沙雷氏菌及其部分纯化的聚氨酯酶对 Impranil®的生物降解在琼脂中得到了证实，形成了一个透明的晕圈。在 30°C 下孵育六天的 Impranil®圆盘接种液化沙雷氏菌后，PU 结构破裂，这可能是由于扫描电子显微镜（SEM）观察到的裂缝形成所致。PCLMDI 薄膜在 60 天的孵育后也被液化沙雷氏菌生物降解，SEM 观察到形成了孔和裂缝。生物降解可能是由于该细菌产生的聚氨酯酶的作用。这项工作通过计算机模拟分析与体外分析相结合，提供了液化沙雷氏菌生物降解 PUs 的潜力的重要信息。
