调节剩余污泥营养结构增强L-乳酸发酵效能及其代谢调控机理研究

The optical purity of synthetic monomer L-lactic acid determines the strength and stability of the biodegradable plastic poly-lactic acid. However, the preparation of L-lactic acid requires costly organic carbon. Thus, it is an attractive topic to researchers to convert organic waste to optically pure L-lactic acid. Waste activated sludge (WAS) generated from waste water treatment plant is a typical organic waste, which contains plenty of protein and various strains for hydrolysis and fermentation. Nevertheless, L-lactic acid is consumed easily in the WAS system which undermines its accumulation. Meanwhile, to improve the optical purity of L-lactic acid, studies often implemented meso- or thermo-condition as well as L-lactic acid bacterial inoculation. There are few studies on regulation of optically pure L-lactic acid using native strains at ambient temperature. According to the points mentioned above, the current study is to balance the trophic structure of WAS via supplementing carbohydrate and lipids, which might improve synergistic hydrolysis of sludge and promote accumulation of L-lactic acid. Base on which, WAS is to be balanced by another kind of organic waste, i.e., food waste and fermentative factors is regulated to enhance the optical purity of L-lactic acid. The mechanism of metabolic regulation towards optically pure L-lactic acid is established from the view of metabolism pathway, hydrolysis and acidification enzyme activity, structure of bacteria and transcript of functional gene and etc. The current study is to enrich the theory of metabolic regulation of L-lactic acid from organic waste fermentation, which provides a new technique of resource recovery for promoting the fermentation of WAS to L-lactic acid. Therefore, it is practical and has certain academic value.

生物可降解塑料聚乳酸的强度及稳定性取决于合成单体L-乳酸的光学纯度，但光学纯L-乳酸的制备需要昂贵的有机碳源，因此有机废物发酵光学纯L-乳酸引起了研究者的广泛关注。污水厂产生的剩余污泥是典型的有机废物，含丰富的蛋白质及水解发酵菌群，但L-乳酸在污泥发酵系统中容易消耗无法积累；同时，现阶段的研究多采用中、高温发酵条件并补加L-乳酸菌以提高L-乳酸光学纯度，少有关于调控土著菌群常温发酵产光学纯L-乳酸的研究。针对上述问题，本项目拟通过碳水化合物及油脂调节剩余污泥营养结构，提高污泥水解并促进L-乳酸积累；进而利用另一类有机废物餐厨垃圾调节剩余污泥，在常温条件下调控发酵因子提高L-乳酸光学纯度；从代谢途径及酶活性、菌群演变及功能基因转录等方面，研究光学纯L-乳酸的代谢调控机理。本项目可丰富有机废物发酵L-乳酸的代谢调控理论，提供促进剩余污泥发酵L-乳酸的资源化技术，具有一定的现实意义与学术价值。

本项目聚焦于有机废物联合发酵制备高纯度乳酸及不同构型的研究中。通过碳水化合物及油脂调节剩余污泥营养结构，提高污泥水解并促进L-乳酸积累；进而利用餐厨垃圾调节剩余污泥，在常温条件下调控发酵因子提高L-乳酸光学纯度；从代谢途径及酶活性、菌群演变及功能基因转录等方面，研究光学纯L-乳酸的代谢调控机理。经过大量实验研究，发现不同底物浓度对产乳酸的发酵影响规律，探索了发酵温度与pH对乳酸构型的交互影响规律，在最佳的发酵条件下，深入研究了ZVI电子传递系统对手性乳酸构型的影响，发现微生物混合菌群体系在还原性零价铁体系中，可以实现较强的水解酸化过程。根据电子势能传递理论，其零价铁缓释体系可以强化水解酸化代谢酶活性。同时利用电发酵体系，说明了发酵代谢系统中电子传递对乳酸构型的代谢计量学影响及机理。在该项目的资助下，实验成果从实验室转化到了中试实验，项目负责人顺利完成了由博士生到初级研究者的转变，为未来的研究打下极为重要的研究基础。本项目的研究成果可丰富有机废物发酵L-乳酸的代谢调控理论及有机废物发酵L-乳酸的资源化技术，具有一定的现实意义与学术价值。