McSwain B S, Irvine R L, Hausner M, Wilderer P A
Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN, USA.
Appl Environ Microbiol. 2005 Feb;71(2):1051-7. doi: 10.1128/AEM.71.2.1051-1057.2005.
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.
在两个具有相同剪切力但沉降时间不同的序批式反应器中培养的絮凝和好氧颗粒污泥中，对胞外聚合物（EPS）进行了定量分析。比较了几种EPS提取方法，以研究不同方法如何影响EPS的化学特性，并使用荧光染料对完整样品和20微米冷冻切片中的EPS进行可视化。反应器1（沉降10分钟）主要富集了污泥体积指数（SVI）为120±12毫升/克的絮凝污泥，反应器2（沉降时间为2分钟）形成了SVI为50±2毫升/克的致密好氧颗粒。使用阳离子交换树脂提取EPS表明，在所有样品中蛋白质比多糖更占主导地位，颗粒状EPS中的蛋白质含量比絮凝状EPS高50%。NaOH和热提取从细胞裂解中产生了更高的蛋白质和多糖含量。颗粒的原位EPS染色表明，细胞和多糖位于颗粒的外缘，而中心主要由蛋白质组成。这些观察结果证实了化学提取数据，并表明颗粒的形成和稳定性取决于非细胞的蛋白质核心。EPS方法的比较解释了细胞裂解和死生物质污染的程度如何导致不同且相反的结论。
