Department of Chemistry , University of Minnesota , Minneapolis , Minnesota 55455-0431 , United States.
Institute of Biogeochemistry and Pollutant Dynamics , ETH Zurich , 8092 Zurich , Switzerland.
Environ Sci Technol. 2019 Mar 5;53(5):2472-2481. doi: 10.1021/acs.est.8b06458. Epub 2019 Feb 15.
Biodegradable polyesters are being increasingly used to replace conventional, nondegradable polymers in agricultural applications such as plastic film for mulching. For many of these applications, poly(butylene adipate- co-terephthalate) (PBAT) is a promising biodegradable material. However, PBAT is also susceptible to photochemical transformations. To better understand how photochemistry affects the biodegradability of PBAT, we irradiated blown, nonstabilized, transparent PBAT films and studied their enzymatic hydrolysis, which is considered the rate-limiting step in polyester biodegradation. In parallel, we characterized the irradiated PBAT films by dynamic mechanical thermal analysis. The rate of enzymatic PBAT hydrolysis decreased when the density of light-induced cross-links within PBAT exceeded a certain threshold. Mass-spectrometric analysis of the enzymatic hydrolysis products of irradiated PBAT films provided evidence for radical-based cross-linking of two terephthalate units that resulted in the formation of benzophenone-like molecules. In a proof-of-principle experiment, we demonstrated that the addition of photostabilizers to PBAT films mitigated the negative effect of UV irradiation on the enzymatic hydrolyzability of PBAT. This work advances the understanding of light-induced changes on the enzyme-mediated hydrolysis of aliphatic-aromatic polyesters and will therefore have important implications for the development of biodegradable plastics.
可生物降解的聚酯越来越多地被用于替代农业应用中的传统不可降解聚合物，例如用于覆盖的塑料薄膜。对于许多这些应用，聚（己二酸丁二醇酯-共对苯二甲酸酯）（PBAT）是一种很有前途的可生物降解材料。然而，PBAT 也容易受到光化学转化的影响。为了更好地了解光化学如何影响 PBAT 的生物降解性，我们辐照了吹塑的、未稳定的透明 PBAT 薄膜，并研究了它们的酶水解，这被认为是聚酯生物降解的限速步骤。同时，我们通过动态力学热分析对辐照 PBAT 薄膜进行了表征。当 PBAT 中光诱导的交联密度超过一定阈值时，酶促 PBAT 水解的速率降低。辐照 PBAT 薄膜的酶水解产物的质谱分析为两个对苯二甲酸单元的基于自由基的交联提供了证据，这导致了苯并酮样分子的形成。在一个原理验证实验中，我们证明了向 PBAT 薄膜中添加光稳定剂可以减轻 UV 辐照对 PBAT 酶促水解性的负面影响。这项工作推进了对光诱导变化对脂肪族-芳香族聚酯的酶介导水解的理解，因此对可生物降解塑料的开发具有重要意义。
