Effect of ultrasonic power density on extracting loosely bound and tightly bound extracellular polymeric substances

Ultrasonication has been widely used for bound extracellular polymeric substance (EPS) extraction. However, the used ultrasonic power density is quite different in literature, which makes their results non-comparable. In this study, the effects of different ultrasonic power densities on extracting bound EPS were assessed via analyzing carbohydrates, proteins, humic acids and DNA. Experimental results proved that ultrasonication power density had a significant effect on loosely bound EPS (LB-EPS) extraction, and an appropriate power density termed critical power density was found to be 35 W/10 mL according to the variations of DNA which represented the intactness or damage of cell membrane. Nevertheless, carbohydrates, proteins and humic acids did not change obviously in tightly bound EPS (TB-EPS) until a very high power density was applied. The critical power density was determined as 65 W/10 mL for TB-EPS extraction. The results indicated that a critical power density should be used in order to extract maximal EPS but not to damage cell membrane intactness. (C) 2013 Elsevier B.V. All rights reserved.