Department of Environmental Systems Science, Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH) Zurich , 8092 Zurich, Switzerland.
Environmental Biochemistry Group, Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (EAWAG) , 8600 Dübendorf, Switzerland.
Environ Sci Technol. 2016 Jan 5;50(1):197-206. doi: 10.1021/acs.est.5b04103. Epub 2015 Dec 17.
Cleavage of ester bonds by extracellular microbial hydrolases is considered a key step during the breakdown of biodegradable polyester materials in natural and engineered systems. Here we present a novel analytical approach for simultaneous detection of changes in the masses and rigidities of polyester thin films during enzymatic hydrolysis using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). In experiments with poly(butylene succinate) (PBS) and the lipase of Rhizopus oryzae (RoL), we detected complete hydrolysis of PBS thin films at pH 5 and 40 °C that proceeded through soft and water-rich film intermediates. Increasing the temperature from 20 to 40 °C resulted in a larger increase of the enzymatic hydrolysis rate of PBS than of nonpolymeric dibutyl adipate. This finding was ascribed to elevated accessibility of ester bonds to the catalytic site of RoL due to increasing polyester chain mobility. When the pH of the solution was changed from 5 to 7, initial hydrolysis rates were little affected, while a softer film intermediate that lead to incomplete film hydrolysis was formed. Hydrolysis dynamics of PBS, poly(butylene adipate), poly(lactic acid), and poly(ethylene terephthalate) in assays with RoL showed distinct differences that we attribute to differences in the polyester structure.
细胞外微生物水解酶对酯键的切割被认为是可生物降解聚酯材料在自然和工程系统中分解的关键步骤。在这里，我们提出了一种新的分析方法，用于使用带有耗散监测的石英晶体微天平（QCM-D）同时检测聚酯薄膜在酶水解过程中质量和刚性的变化。在聚丁二酸丁二醇酯（PBS）和米根霉脂肪酶（RoL）的实验中，我们在 pH 5 和 40°C 下检测到 PBS 薄膜的完全水解，该水解过程经历了柔软且富含水的薄膜中间产物。将温度从 20°C 升高到 40°C 导致 PBS 的酶水解速率比非聚合的二丁酸丁酯增加更大。这一发现归因于由于聚酯链的流动性增加，酯键对 RoL 的催化部位的可及性提高。当溶液的 pH 值从 5 变为 7 时，初始水解速率几乎没有受到影响，而形成了导致不完全薄膜水解的更柔软的薄膜中间产物。RoL 实验中 PBS、聚己二酸丁二醇酯、聚乳酸和聚对苯二甲酸乙二醇酯的水解动力学表现出明显的差异，我们将其归因于聚酯结构的差异。
