temperature (25 8C, 40 8C and 60 8C) all surfaces exhibit a more or
less inhomogeneous adlayer. In all cases, black ovals or circles
occurr indicating EPS-or carbohydrate-free areas. In addition, the
grooves due to the grinding process of sample preparation are still
visible. This implies that EPS or in this case the FM-detectable
carbohydrates only adsorb to small extent and form a patchy layer.
3.2 Behaviour of the adsorbates in liquid phase
In order to study the stability of the layer in liquid phase the EPStreated
samples were mounted as set of three samples into a
bottle (250 mL) containing sterile PGC nutrient solution and kept
at 30 8C in the dark for three days. Each bottle contained only
samples treated for EPS adsorption at the same temperature. All
samples were immersed totally in the liquid. Figure 3 shows FMimages
characteristic for the given adsorption temperature.
Whereas the images of the upper half show only small intensities
the images of the lower half exhibit strong intensity indicating the
presence of the adsorbate even after exposure to nutrient solution
for 3 days. This shows that some part of the EPS stays stable on
the surface. In addition, readsorption of probably dissolved
adsorbates on the upper part of the samples does not occur.
Figure 4 shows magnified views of the right column of Fig. 3. Thesamples treated with EPS at 40 or 60 8C reflect a surface with a
layer of higher density when compared to those achieved at 25 8C.