As concerns increase regarding sustainable industries and environmental pollutions caused by the accumulation of non-degradable plastic wastes, bio-based polymers, particularly biodegradable plastics, have attracted considerable attention as potential candidates for solving these problems by substituting petroleum-based plastics. Among these candidates, polyhydroxyalkanoates (PHAs), natural polyesters that are synthesized and accumulated in a range of microorganisms, are considered as promising biopolymers since they have biocompatibility, biodegradability, and material properties similar to those of commodity plastics. Accordingly, substantial efforts have been made to gain a better understanding of mechanisms related to the biosynthesis and properties of PHAs and to develop natural and recombinant microorganisms that can efficiently produce PHAs comprising desired monomers with high titer and productivity for industrial applications.

Recent advances in biotechnology, including those related to evolutionary engineering, synthetic biology, and systems biology, can provide efficient and effective tools and strategies that reduce time, labor, and costs to develop microbial platform strains that produce desired chemicals and materials. Adopting these technologies in a systematic manner has enabled microbial fermentative production of non-natural polyesters such as poly(lactate) [PLA], poly(lactate-co-glycolate) [PLGA], and even polyesters consisting of aromatic monomers from renewable biomass-derived carbohydrates, which can be widely used in current chemical industries.

In this review, we present an overview of strain development for the production of various important natural PHAs, which will give the reader an insight into the recent advances and provide indicators for the future direction of engineering microorganisms as plastic cell factories. On the basis of our current understanding of PHA biosynthesis systems, we discuss recent advances in the approaches adopted for strain development in the production of non-natural polyesters, notably 2-hydroxycarboxylic acid-containing polymers, with particular reference to systems metabolic engineering strategies.

由于对不可降解塑料废料的积累引起的可持续工业和环境污染的关注日益增加，生物基聚合物，特别是可生物降解的塑料，已成为替代石油基塑料解决这些问题的潜在候选者，引起了相当大的关注。在这些候选物中，聚羟基链烷酸酯（PHA）是在多种微生物中合成和积累的天然聚酯，被认为是有前途的生物聚合物，因为它们具有与商品塑料相似的生物相容性，生物降解性和材料特性。因此，

生物技术的最新进展，包括与进化工程，合成生物学和系统生物学有关的进展，可以提供有效而有效的工具和策略，从而减少开发生产所需化学物质和材料的微生物平台菌株所需的时间，劳动力和成本。以系统的方式采用这些技术已使微生物发酵生产非天然聚酯，例如聚乳酸[PLA]，聚乳酸-乙醇酸共聚物[PLGA]，甚至包括由可再生生物质-衍生的碳水化合物，可广泛用于当前的化学工业中。

在本文中，我们概述了用于生产各种重要天然PHA的菌株开发概况，这将使读者了解最新进展，并为工程微生物作为塑料细胞工厂的未来发展方向提供指标。根据我们对PHA生物合成系统的当前了解，我们讨论在生产非天然聚酯（尤其是含2-羟基羧酸的聚合物）中用于菌株开发的方法的最新进展，特别是参考系统代谢工程策略。