Given their ubiquity in modern society, the development of biodegradable and renewably sourced plastics is essential for the creation of an environmentally sustainable society. One of the drawbacks for currently available biodegradable plastics such as poly(l-lactic acid) (PLLA) and polyhydroxyalkanoates (PHAs) is that it is difficult to simultaneously achieve mechanical flexibility and certain crystallization behavior in these materials, which limits their use as replacements for established petroleum-based plastics such as isotactic polypropylene (iPP). Here, we report the synthesis and characterization of a new biodegradable plastic, poly(3-hydroxy-2-methylbutyrate) [P(3H2MB)], which is a member of the bacterial PHA family whose members include an α-methylated monomer unit. Biosynthesis of P(3H2MB) was achieved using recombinant Escherichia coli expressing an engineered pathway. Biosynthesized P(3H2MB) exhibited the highest melting temperature (197 °C) among the biosynthesized PHAs and improved thermal resistance. It also exhibited improved crystallization behavior and mechanical flexibility nearly equal to those of iPP. The primary nucleation rate of P(3H2MB) was faster than that of P(3HB), and the spherulite morphology of P(3H2MB) was much finer than that of P(3HB). This crystal morphology may result in more rapid crystallization behavior, increased transparency, and enhanced mechanical properties. The superior physical properties of P(3H2MB) have the potential to open new avenues for the production of high-performance biodegradable plastics for replacing petroleum-based bulk commodity plastics.

鉴于它们在现代社会中无处不在，开发可生物降解和可再生来源的塑料对于建立环境可持续的社会至关重要。当前可用的可生物降解塑料的缺点之一，例如聚（l）-乳酸）（PLLA）和聚羟基链烷酸酯（PHA）的特点是很难在这些材料中同时实现机械柔韧性和某些结晶行为，这限制了它们用作替代等规聚丙烯（iPP）等成熟的石油基塑料的用途。在这里，我们报告了一种新型的可生物降解的塑料，聚（3-羟基-2-甲基丁酸酯）[P（3H2MB）]的合成和表征，它是细菌PHA家族的成员，其成员包括一个α-甲基化的单体单元。P（3H2MB）的生物合成使用重组实现大肠埃希氏 杆菌表达工程途径。在生物合成的PHA中，生物合成的P（3H2MB）表现出最高的熔融温度（197°C），并且具有更高的耐热性。它还表现出改善的结晶行为和机械柔韧性，几乎与iPP相同。P（3H2MB）的一次成核速率比P（3HB）的成核速率快，P（3H2MB）的球晶形貌比P（3HB）的球晶形更好。这种晶体形态可以导致更快的结晶行为，增加的透明度和增强的机械性能。P（3H2MB）的优异物理性能有可能为生产高性能的可生物降解塑料以替代石油基大宗商品塑料开辟新的途径。