Extracellular Polymeric Substances Extraction Research Articles

Extraction of extracellular polymeric substances (EPS) from biofilms using a cation exchange resin

A cation exchange resin was used to extract water soluble EPS material from different sewer biofilms and a biofilm monoculture of P.putida. The extraction method seemed to be especially suitable for extracting humic substances and proteins from biofilms but also carbohydrate could be extracted, depending on the nature of the sample. Extraction conditions must be well defined because the extraction efficiency was dependent on stirring intensity, amount of cation exchange resin and extraction time. Up to 20% of the total biofilm protein was found in the DOWEX-extractable fraction. No significant cell-lysis up to 2 hours of extraction time could be detected by acridine orange (AO) direct counts. The same was true when applying the extraction method to a batch culture of P.putida. However, the number of viable cells in the batch culture as recorded by plate count technique was reduced to 28 % after 30 min of extraction. In conclusion, proteins and humic substances can be extracted from biofilm EPS in considerable amounts and should be investigated more in detail when analysing the properties of the EPS matrix of a biofilm.

Enzymatic activity in the activated-sludge floc matrix.

The enzymatic activity of activated sludge was investigated with special emphasis on the localization of the enzymes in the sludge floc matrix. Activated sludge from an advanced activated-sludge treatment plant, performing biological N and P removal, was used. An enzymatic fingerprint was established using a panel of six different enzymes. The fingerprint revealed peptidase as the most dominating specific enzyme tested. By monitoring sludge bulk enzymatic activity over a 3-month period using fluorescein diacetate as an enzyme substrate, considerable variations in activity were observed even over short periods (a few days). The variation in esterase activity was to some extent correlated to the presence of humic compounds in the sludge, but not to the sludge protein content. Comparison of full sludge enzyme activity to the activity of a batch-grown sludge culture indicated that enzymes accumulated in sludge flocs. A large proportion of the exoenzymes were immobilized in the sludge by adsorption in the extracellular polymeric substances (EPS) matrix. This was demonstrated by extraction of EPS from the activated sludge using cation exchange. Contemporary to the release of EPS a very large fraction of the exoenzymes was released into the water. This showed that the exoenzymes should be considered to be an integrated part of the EPS matrix rather than as direct indicators of the microbial activity or biomass.

Extraction of extracellular polymeric substances (EPS) from biofilms using a cation exchange resin

A cation exchange resin was used to extract water soluble EPS material from different sewer biofilms and a biofilm monoculture of P.putida. The extraction method seemed to be especially suitable for extracting humic substances and proteins from biofilms but also carbohydrate could be extracted, depending on the nature of the sample. Extraction conditions must be well defined because the extraction efficiency was dependent on stirring intensity, amount of cation exchange resin and extraction time. Up to 20% of the total biofilm protein was found in the DOWEX-extractable fraction. No significant cell-lysis up to 2 hours of extraction time could be detected by acridine orange (AO) direct counts. The same was true when applying the extraction method to a batch culture of P.putida. However, the number of viable cells in the batch culture as recorded by plate count technique was reduced to 28 % after 30 mm of extraction. In conclusion, proteins and humic substances can be extracted from biofilm EPS in considerable amounts and should be investigated more in detail when analysing the properties of the EPS matrix of a biofilm.