Comparison of extraction methods for quantifying extracellular polymers in activated sludges

The efficacies of extracting, extracellular polymeric substances (EPS) from aerobic activated sludge samples using five commonly used extraction methods - steaming extraction, heating (80 degrees C), EDTA extraction, cation exchange resin, and formaldehyde plus NaOH were compared. EPS extraction yields were represented by total organic carbon (TOC), and the amount of cell lysis during the extractions was indicated by DNA concentration. Results show that heat treatment was most effective in extracting, EPS for all sludges, and only 0.5-0.7 % of DNA in the sludge samples were detected, suggesting the extracted EPS were not contaminated by intracellular substances. Among the extraction methods, the heat treatment extraction gave the highest carbohydrate and protein yields, followed by the steaming extraction method, whereas the other three extraction methods gave approximately equivalent amounts of carbohydrates and proteins for the three sludge samples.