Structural extracellular polymeric substances (SEPS) as valuable biopolymers, can be extracted from waste activated sludge (WAS). However, the extraction yield is typically low, and detailed information on SEPS characterizations, as well as proper treatment of the sludge after SEPS extraction, remains limited. This study aimed to optimize the conditions of heating-Na2CO3 extraction process to increase the yield of SEPS extracted from WAS. Subsequently, SEPS were characterized, and, for the first time, insights into their protein composition were uncovered by using proteomics. A maximum SEPS yield of 209 mg g-1 volatile solid (VS) was obtained under optimal conditions: temperature of 90 °C, heating time of 60 min, Na+ dosage of 8.0 mmol/g VS, and pH required to precipitation of 4.0, which was comparable to that from the aerobic granular sludge reported in literature. Proteomics analysis unveiled that the proteins in SEPS primarily originated from microorganisms involved in nitrogen fixation and organic matter degradation, including their intracellular and membrane-associated regions. These proteins exhibited various catalytic activities and played crucial roles in aggregation processes. Besides, the process of SEPS extraction significantly enhanced volatile fatty acid (VFA) production during the anaerobic fermentation of residual WAS after SEPS extraction. A maximum VFA yield of 420 ± 14 mg COD/g VSadded was observed in anaerobic fermentation of 10 d, which was 77.2 ± 0.1 % higher than that from raw sludge. Mechanism analysis revealed that SEPS extraction not only improved WAS disintegration and solubilization but also reduced the relative activity of methanogens during anaerobic fermentation. Moreover, SEPS extraction shifted the microbial population during anaerobic fermentation in the direction towards hydrolysis and acidification such as Fermentimonas sp. and Soehngenia sp. This study proposed a novel strategy based on SEPS extraction and VFA production for sludge treatment, offering potential benefits for resource recovery and improved process efficiency.

中文翻译：

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一种废弃活性污泥处理的新策略：结构性细胞外聚合物物质的回收和挥发性脂肪酸的发酵生产


结构性细胞外聚合物 （SEPS） 作为有价值的生物聚合物，可以从废弃活性污泥 （WAS） 中提取。然而，提取率通常较低，并且有关 SEPS 特征以及 SEPS 提取后污泥适当处理的详细信息仍然有限。本研究旨在优化加热-Na2CO3 提取工艺的条件，以提高从 WAS 中提取的 SEPS 的产量。随后，对 SEPS 进行了表征，并首次通过使用蛋白质组学揭示了对其蛋白质组成的见解。在最佳条件下，温度为 90 °C，加热时间 60 min，Na+ 剂量为 8.0 mmol/g VS，沉淀所需 pH 值为 4.0，与文献报道的好氧颗粒污泥相当，获得 209 mg g-1 挥发性固体 （VS） 的产量。蛋白质组学分析显示，SEPS 中的蛋白质主要来源于参与固氮和有机物降解的微生物，包括它们的细胞内和膜相关区域。这些蛋白质表现出各种催化活性，并在聚集过程中发挥关键作用。此外，SEPS 提取过程显著增强了 SEPS 提取后残留 WAS 厌氧发酵过程中挥发性脂肪酸 （VFA） 的产生。厌氧发酵 10 d 时，观察到 14 mg COD/g VSadded 的最大 VFA 产率为 420 ± 14 mg COD/g VSadded，比原污泥高 77.2 ± 0.1 %。机制分析表明，SEPS 提取不仅改善了 WAS 的崩解和溶解，而且降低了厌氧发酵过程中产甲烷菌的相对活性。 此外，SEPS 提取使厌氧发酵过程中的微生物种群向水解和酸化方向移动，例如 Fermentimonas sp. 和 Soehngenia sp.本研究提出了一种基于 SEPS 提取和 VFA 生产的新污泥处理策略，为资源回收和提高工艺效率提供了潜在的好处。