Composition and Distribution of Extracellular Polymeric Substances in Aerobic Flocs and Granular Sludge
AUTOR(ES)
McSwain, B. S.
FONTE
American Society for Microbiology
RESUMO
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-μm 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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=546788Documentos Relacionados
- Bacterial survival and association with sludge flocs during aerobic and anaerobic digestion of wastewater sludge under laboratory conditions.
- Composition of Extracellular Polymeric Substances (EPS) produced by Flavobacterium columnare isolated from tropical fish in Brazil
- Bacteriological composition and structure of granular sludge adapted to different substrates.
- Importance of Extracellular Polymeric Substances from Thiobacillus ferrooxidans for Bioleaching
- Sequencing batch reactor operation for treating wastewater with aerobic granular sludge