Composition and distribution of extracellular polymeric substances in aerobic flocs and granular sludge
Composition and distribution of extracellular polymeric substances in aerobic flocs and granular sludge
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DOI：
10.1128/aem.71.2.1051-1057.2005
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发表时间：
2005-02-01
影响因子：
4.4
通讯作者：
Wilderer, PA
中科院分区：
文献类型：
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作者：
McSwain, BS;Irvine, RL;Wilderer, PA
在两个剪切力相同但沉淀时间不同的序批式反应器中，对絮凝颗粒污泥和好氧颗粒污泥中的胞外聚合物(EPS)进行了定量。比较了几种提取EPS的方法，研究了不同方法对EPS化学特性的影响，并使用荧光染色对完整样品和20微米冰冻切片中的EPS进行了可视化。反应器1(运行10min)主要浓缩絮凝污泥，污泥体积指数(SVI)为120+/-12mlg(-1)，反应器2(停留时间2min)形成致密好氧颗粒，SVI为50+/-2mlg(-1)。阳离子交换树脂提取EPS表明，所有样品中蛋白质含量高于多糖，颗粒状EPS的蛋白质含量比絮凝性EPS高50%。氢氧化钠和热浸提细胞裂解产物中的蛋白质和多糖含量较高。颗粒的EPS原位染色显示，细胞和多糖定位于颗粒的外缘，而颗粒的中心主要由蛋白质组成。这些观察证实了化学提取数据，并表明颗粒的形成和稳定性依赖于非细胞的蛋白质核心。EPS方法的比较解释了显著的细胞裂解和死亡生物体的污染如何导致不同和相反的结论。
Extracellular polymeric substances (EPS) were quantified in flocculent and aerobic granular sludge developed in two sequencing batch reactors with the same shear force but different settling times. Several EPS extraction methods were compared to investigate how different methods affect EPS chemical characterization, and fluorescent stains were used to visualize EPS in intact samples and 20-mum cryosections. Reactor 1 (operated with a 10-min settle) enriched predominantly flocculent sludge with a sludge volume index (SVI) of 120 +/- 12 ml g(-1), and reactor 2 (2-min settle time) formed compact aerobic granules with an SVI of 50 +/- 2 ml g(-1). EPS extraction by using a cation-exchange resin showed that proteins were more dominant than polysaccharides in all samples, and the protein content was 50% more in granular EPS than flocculent EPS. NaOH and heat extraction produced a higher protein and polysaccharide content from cell lysis. In situ EPS staining of granules showed that cells and polysaccharides were localized to the outer edge of granules, whereas the center was comprised mostly of proteins. These observations confirm the chemical extraction data and indicate that granule formation and stability are dependent on a noncellular, protein core. The comparison of EPS methods explains how significant cell lysis and contamination by dead biomass leads to different and opposing conclusions.