利用生物可降解塑料替代传统石油基塑料成为从源头解决塑料污染的新路径，聚羟基脂肪酸酯（PHA）是目前唯一一类从前体物到产品均由微生物合成的有机高分子聚合物。同时，PHA具备良好的可降解性能且符合制备塑料产品要求。本论文使用混合菌群以废弃有机物（餐厨废物、白酒废水）为底物进行PHA合成工艺优化研究，针对现有工艺中PHA产品性能不足以及产率低等问题开展研究：首先，餐厨废物在不同接种微生物条件下合成中链脂肪酸（MCFA），其中污泥和窖泥混合后作为接种物厌氧发酵效能最优，显著高于污泥和窖泥接种物单独发酵，混合接种物具有较高的脂肪酸生物合成以及碳水化合物代谢基因更有利于MCFA合成。另外，两阶段发酵相比一阶段发酵的MCFA浓度提高了4.3 gCOD/L。分析厌氧发酵产物代谢途径发现丁醇、己醇的生成和己酸合成产生了代谢竞争。然后，建立两个序批式富集反应器SBR1（无菌产酸液）和SBR2富集PHA合成菌群，富集稳定后SBR1的PHA积累能力显著高于SBR2。微生物群落在属水平上显示优势菌种均为PHA合成菌（Paracoccus和Thauera），而且PHA合成菌在富集过程的微生物生态网络中主要起核心和模块间连接作用。在不同底物合成实验中丁酸型产酸液作为底物表现出最高的YPHA/S和qPHA，仅有己酸作为底物能合成3HHx单体，3HHx单体能显著提高PHA的分子量、热力学和力学性能。另外，建立序批式生物膜反应器（SBBR）和SBR进行菌群高密度培养和稳定富集实验，SBBR稳定运行的活性生物量浓度和PHA积累率分别为13.9 g/L和35.2 wt%均显著高于SBR。此外，SBBR在中负荷条件下（6000 mg COD/L/d）富集效率最高，菌群中PHA合成菌群高度富集，PHA功能菌相对丰度达到为73.6%。此外，SBBR中酰化高丝氨酸内酯（AHL）的积累促进了PHA合成菌的富集。PHA积累率主要是受微生物组成以及AHL影响，而菌群生物量浓度主要受SVI影响。最后，在PHA合成实验中接种生物量为10 g/L时YPHA/S和YX/S最高，连续流补料更有利于高生物浓度进行PHA合成。开展PHA提取实验，菌群经过超声和热提取法预处理后PHA回收效率显著升高。高压破碎在20 MPa条件下提取效率最高，氯仿和碳酸二甲酯的PHA回收效率高于其它有机溶剂，而SDS消解联合超声处理的最优条件为SDS浓度为5 g/L消解30 min。相较于物理法，化学法NaClO提取会导致PHA样品热稳定性和分子量显著下降。

Using biodegradable plastics to replace traditional petroleum-based plastics has become a new approach to solve plastic pollution at the source. Polyhydroxyalkanoates (PHA) are currently the only type of organic polymer synthesized by microorganisms from precursors to products, with good degradability and meeting the requirements for the preparation of plastic products. In this paper, the mixed flora is used to optimize the PHA synthesis process with waste organic matter (food waste, liquor wastewater) as substrate, and research was carried out on the problems such as insufficient performance and low yield of PHA products in the existing process:Firstly, the synthesis of medium-chain fatty acids (MCFA) from food waste under different microbial inoculation conditions, the anaerobic fermentation efficiency of sludge and pit mud as mixed inoculants was the best, significantly higher than the fermentation of sludge and pit mud inoculants alone. The mixed inoculants had higher fatty acid biosynthesis and carbohydrate metabolism genes, which were more conducive to MCFA synthesis. Additionally, the concentration of MCFA in two-stage fermentation was 4.3 gCOD/L higher than that in one-stage fermentation. The production of butanol and hexanol and the synthesis of caproic acid in the fermentation reactor formed metabolic competition.Then, two sequential batch reactor (SBR) systems were established to enrich PHA-synthesizing bacterial communities, SBR1 (sterile substrate) and SBR2. After stable enrichment, the PHA accumulation capacity of SBR1 was significantly higher than that of SBR2. At the genus level, the dominant bacterial species in the microbial community were PHA-synthesizing bacteria (Paracoccus and Thauera), and PHA-synthesizing bacteria mainly played a role in connecting the core and modules in the microbial ecological network during the enrichment process. In different substrate synthesis experiments, butyrate-fermentation broth as a substrate showed the highest YPHA/S and qPHA, and only caproate as a substrate could synthesize 3HHx monomer, which could significantly improve the molecular weight, thermodynamic and mechanical properties of PHA.In addition, the establishment of sequencing batch reactor (SBBR) and SBR for high-density cultivation and stable enrichment experiments of bacterial communities showed that the stable operating active biomass concentration and PHA accumulation rate of SBBR were 13.9 g/L and 35.2 wt%, respectively, significantly higher than those of SBR. Additionally, SBBR had the highest enrichment efficiency under medium organic load conditions (6000 mgCOD/L/d), with a high enrichment of PHA synthesis bacteria in the bacterial community, and the relative abundance of PHA functional bacteria reached 73.6%. In addition, the accumulation of acylated homoserine lactone (AHL) in SBBR promoted the enrichment of PHA synthesis bacteria. Therefore, the PHA accumulation rate was mainly affected by microbial composition and AHL, while the bacterial biomass concentration was mainly affected by SVI.Finally, in the PHA synthesis experiment, YPHA/S and YX/S were the highest when the inoculation biomass was 10 g/L, and continuous flow feeding was more conducive to high biomass for PHA synthesis.In the PHA extraction experiment, the recovery efficiency of PHA significantly increased after the microbial community was pretreated by ultrasonic and thermal extraction methods.High-pressure crushing had the highest extraction efficiency at 20 MPa, and the extraction efficiency of PHA with chloroform and dimethyl carbonate was higher than that of other organic solvents. The optimal condition for SDS digestion combined with ultrasonic treatment was SDS concentration of 5 g/L for 30 minutes. Compared with physical wall-breaking methods, chemical extraction with NaClO resulted in significant decreases in thermal stability and molecular weight of PHA samples.