Polylactide (PLA) is a biobased synthetic polyester with diverse commercial applications. Nevertheless, PLA has been deemed unfavorable owing to its constrained processability, impact resistance, and biodegradability. Therefore, this study aimed at engineering novel biodegradable modifiers based on a highly chiral enantiopure D-lactate (D-LA)-based polyester called poly[D-LA-co-(R)-3-hydroxybutyrate (3HB)] (LAHB) to improve the physical properties of PLA. High-molecular-weight (hmw) LAHB was synthesized from the chemoautotrophic Cupriavidus necator in substantial quantities. The tailor-made overproduction of LAHB was achieved by using a minimal medium containing glucose and retaining the intrinsic synthetic pathway for the 3HB homopolymer in C. necator, which produced the highest yields, reaching up to 27 g/L/48 h. The molecular weight of LAHB substantially elevated up to 1.1 × 10⁶ g/mol and was termed ultrahigh-molecular-weight (uhmw) LAHB. The LA faction in LAHB was modulated via a synergistic optimized combination of the lactate dehydrogenase and propionyl-coenzyme A transferase variants as well as by effective shut-off of the D-LA escape route. Combination of PLA and the two selected biodegradable uhmw-/hmw-LAHBs as demand-oriented biodegradable modifiers allowed improved processability and impact resistance of PLA while retaining transparency. These benefits of LAHB are distinguishable from those of conventional biobased modifiers, including 3HB-based polymers.

中文翻译：

---

用于定制生产可生物降解聚丙交酯改性剂的微生物平台：超高分子量乳酸酯聚酯 LAHB

聚丙交酯 (PLA) 是一种具有多种商业应用的生物基合成聚酯。然而，由于其加工性、抗冲击性和生物降解性有限，PLA 被认为是不利的。因此，本研究旨在设计基于高度手性对映体纯 D-乳酸 (D-LA) 聚酯的新型可生物降解改性剂，称为聚[D-LA- co- ( R )-3-羟基丁酸酯 (3HB)] (LAHB)改善PLA的物理性能。高分子量 (hmw) LAHB 是由化能自养性Cupriavidus necator大量合成的。通过使用含有葡萄糖的基本培养基并保留C. necator中 3HB 均聚物的固有合成途径，实现了 LAHB 的定制过量生产，其产量最高，达到 27 g/L/48 h。 LAHB的分子量大幅提高至1.1×10 ⁶ g/mol，被称为超高分子量（uhmw）LAHB。 LAHB 中的 LA 部分是通过乳酸脱氢酶和丙酰辅酶 A 转移酶变体的协同优化组合以及有效关闭 D-LA 逃逸途径来调节的。 PLA 与两种选定的可生物降解超高分子量/高分子量 LAHB 的组合作为以需求为导向的可生物降解改性剂，可以提高 PLA 的加工性能和抗冲击性，同时保持透明度。 LAHB 的这些优点与传统生物基改性剂（包括 3HB 基聚合物）的优点截然不同。