Gabirondo Elena, Maiz-Iginitz Ainhoa, Ximenis Marta, Świderek Katarzyna, Andrés-Sanz Daniel, Moliner Vicent, Cabedo Luis, Westlie Andrea H, Chen Eugene Y-X, Cerrón-Infantes Daniel Alonso, Unterlass Miriam M, López-Gallego Fernando, Etxeberria Agustin, Sardon Haritz
POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU Donostia-San Sebastián 20018 Spain
Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA) Paseo de Miramon 182 San Sebastián Spain.
Chem Sci. 2025 Jul 4. doi: 10.1039/d5sc02196k.
Polyhydroxyalkanoates (PHAs) are receiving significant attention due to their biobased origin, biodegradability, and excellent barrier properties. However, their high cost compared to traditional plastics necessitates the development of recycling technologies to retain their value post-use. Despite being thermoplastics, PHAs are difficult to recycle mechanically due to their narrow processing window, particularly for polyhydroxybutyrate (PHB), and conventional chemical recycling routes often lead to non-selective degradation and dehydration to crotonic acid, yielding complex product mixtures with limited valorization potential. In contrast, this study presents a selective chemical recycling method for PHB that suppresses dehydration pathways by using naturally occurring taurine as an organocatalyst. Taurine outperforms other catalyst families, such as Brønsted acids and bases, in terms of depolymerization yield and selectivity, achieving 98% enantiomerically pure 3-hydroxybutyric acid (HBA) in the optimized process. Density functional theory (DFT) calculations provided insights into the pH-dependent HBA elimination mechanisms demonstrating that taurine does not play a role in this process under very basic nor acidic conditions. A liquid-liquid extraction technique was developed to separate HBA from by-product crotonic acid, successfully maintaining the -enantiomeric form of the recovered HBA. This method is applicable to both synthetic PHB and biological PHB samples, including copolymers and blends. Overall, this taurine-catalyzed PHB depolymerization approach inhibits the formation of dehydrated by-products and offers a promising solution for selective recycling of PHB into valuable chiral building blocks.
聚羟基脂肪酸酯(PHA)因其生物基来源、可生物降解性和优异的阻隔性能而受到广泛关注。然而,与传统塑料相比,它们的成本较高,因此需要开发回收技术以在使用后保留其价值。尽管PHA是热塑性塑料,但由于其加工窗口狭窄,特别是对于聚羟基丁酸酯(PHB),机械回收难度较大,而传统的化学回收路线往往导致非选择性降解和脱水生成巴豆酸,产生具有有限增值潜力的复杂产物混合物。相比之下,本研究提出了一种用于PHB的选择性化学回收方法,该方法通过使用天然存在的牛磺酸作为有机催化剂来抑制脱水途径。在解聚产率和选择性方面,牛磺酸优于其他催化剂家族,如布朗斯特酸和碱,在优化过程中可实现98%对映体纯的3-羟基丁酸(HBA)。密度泛函理论(DFT)计算深入了解了pH依赖性HBA消除机制,表明牛磺酸在非常碱性或酸性条件下在该过程中不起作用。开发了一种液-液萃取技术,用于从副产物巴豆酸中分离HBA,成功保持了回收HBA的对映体形式。该方法适用于合成PHB和生物PHB样品,包括共聚物和共混物。总体而言,这种牛磺酸催化的PHB解聚方法抑制了脱水副产物的形成,为将PHB选择性回收为有价值的手性结构单元提供了一种有前景的解决方案。