Method evaluation of extracellular polymeric substances extraction from Anammox granular sludge with compact structure

As a major component of the matrix in granular sludge (GS), extracellular polymeric substance (EPS) is crucial in formation and stabilization of compact structure. Thus, the selection of appropriate extraction methods is of great importance, affecting the yield, composition, and the properties of EPS. However, there is still lack of the standard methods for EPS extraction. In present study, several commonly used methods were applied for extracting EPS from anaerobic ammonium oxidation (Anammox) GS, and the effectiveness of these methods were evaluated. The methods of heating, and formaldehyde with NaOH were found to obtain a higher EPS yield rate, compared to the other methods. The collected EPS was found to mainly consist of proteins (PN) and polysaccharides (PS). The high PN/PS values obtained in most methods indicated that protein content was substantially enriched in the granules. Moreover, the dominance of amide bands and/or polysaccharide -associated bands in the EPS was also revealed in the results of Attenuated total reflectance-Fourier transform infrared spectra.