采用复合菌群以剩余污泥水解液为基质合成生物可降解塑料——聚羟基脂肪酸酯（PHA），对于降低PHA生产成本、实现污泥的减量化和资源化具有十分重要的意义，但是水解液高碳不限氮的基质特点，以及成分的复杂和不稳定性，给实际应用造成了困难。因此，研究水解液基质条件下复合菌群合成PHA的规律及影响因素，对于该项技术的发展具有重要的理论价值和实践指导意义。本文首先以水解液的主要产物挥发性脂肪酸（VFAs）为基质，研究了复合菌群在高碳（TOC>2000mg/L）不限氮（C/N=10）条件下PHA的积累规律。结果表明：在丰盛-饥饿模式下，最高PHA合成率PHAs%（62.43%，以细胞干重计）和合成量（0.71gPHA/L）于碳源殆尽时获得，N、P营养元素处于过剩状态并影响活细胞生物量的变化，动力学分析表明PHA积累占主导（YP/S≈3YX/S）。复合菌群优先利用偶数碳酸合成HB，然后利用奇数碳酸合成HV。硝化抑制剂硫脲对PHA合成有一定促进作用。其次，VFAs组成对PHA合成过程及产品中HV的比例有重要影响。以乙酸、丙酸、丁酸、戊酸单独作为碳源，发现四种酸的利用速率和PHAs%乙酸>丁酸>丙酸>戊酸，说明菌群优先利用短链和偶数碳酸进行PHA合成。以不同摩尔比（1:3、1:1、3:1）的乙酸/丙酸、丁酸/戊酸混合物作为碳源，HV单体比例随着奇数碳酸的比例升高而升高，表明奇数碳酸的增加有利于生成HV。乙/丙酸组的PHA产率YP/S均高于丁/戊酸组，表明短链酸有利于提高底物-PHA转化率。最后，水解液中非VFAs物质（蛋白质、糖类等）对于碳源在细胞生长和PHA积累两过程中的分配有重要影响。以牛血清蛋白BSA、葡萄糖作为模式物质研究发现，非VFAs比例的增加（0~50%）不利于PHA的积累，但可促进细胞生长。相同非VFAs比例下，糖类为主要非VFAs的水解液合成PHA要优于以蛋白质为主要非VFAs的水解液。葡萄糖、BSA、酵母粉三种非VFAs单独作为碳源时，均不能很好的积累PHA，说明其不是该菌群合成PHA的理想碳源。综上，VFAs比例较高且奇数碳酸较多的污泥水解液，有利于获得较高的合成率以及品质较好的产品，此外，应综合平衡菌体生长和PHA积累两过程确定合理的收菌时间以获得较高的PHA产量。
It is of great significance to synthesize polyhydroxyalkanoates (PHA) by bacterial consortium from the excess sludge fermentation liquid which will greatly lower the cost of PHA production and result in the sludge reduction and recycling. However, the high initial carbon concentration without limit of nitrogen in sludge fermentation liquid and its complexity and instability of components limits the hydrolysate application in actual PHA production. Therefore, it is important to study the laws and kinetics of PHA production by bacterial consortium from sludge fermentation liquid in order to provide theoretical guidance and technical support for the technology development.Firstly, the laws of PHA accumulation by bacterial consortium under high initial carbon source concentration and nitrogen-unlimited conditions were studied in substrate of mixed violatile fatty acids (VFAs), which were the main components of fermented liquid. It shows that under feast and famine regime, the highest PHA content (62.43%, of cell dry weight) and PHA yield (0.71g/L) were obtained when carbon was exhausted. The surplus nitrogen and phosphorus as the essential elements influenced the active cell growth. Kinetics analysis indicated that PHA accumulation was the predominant in the process comparing with the cell growth(YP/S≈3YX/S). The consortium was prior to utilize even number carbon acids to synthesize HB and then the odd number carbon acids for HV. The thiourea, one kind of nitrification inhibitors, could facilitate the PHA synthesis.Secondly, the composition of VFAs played an important role in the PHA synthesis as well as the HV content in the PHA. When acetic acid, propionic acid, butyric acid and iso-valeric acid was adopted as the sole carbon source separately, both of the substrate uptake rate and PHAs% were acetic acid > butyric acid > propionic acid > iso-valeric acid, indicating that the bacteria consortium was prior to use short-chain and even-number carbon sources for PHA synthesis. When the mixture of acetate/propionic acids and butyric/iso-valeric acids were adopted as carbon source, the HV monomer ratio increased with the ratio of odd-number carbon acids(1:3, 1:1, 3:1) in substrates, indicating that odd-number carbon acids favored HV synthesis. The group using acetic acid and propionic acid as carbon source presented a higher yield of PHA (YP/S) than that of butyric acid and pentanoic acid, indicating that short chain VFAs were favorable for the transformation from substrates to PHA. Finally, the non-VFAs in sludge fermentation liquid (such as soluble proteins and carbohydrates, etc) played an important role in the allocation of carbon source between cell growth and PHA accumulation. Taking the bovine serum albumin (BSA) and glucose as model substrates, it showed that an increase of non-VFAs content (0~50%) facilitated the cell growth while restrained the PHA accumulation. With the same non-VFAs content, the sludge fermentation liquid with carbohydrates as the main non-VFAs will be better for PHA synthesis than that with the protein as the main non-VFAs. When using the glucose, BSA and yeast extract as the sole carbon substrate separately, none of the consortium accumulated PHA well, indicating none of these carbon sources was ideal substrate for the bacteria consortium to accumulate PHA.In conclusion, sludge fermentation liquid with higher content of VFAs and odd-number carbon acids, will probably obtain a relatively high content as well as a better quality of the PHA product. Besides, a balance should be found between cell growth and PHA accumulation in order to achieve a relative high PHA yield.
