Extraction of EPS - extracellular polymeric substances, formaldehyde extraction mechanism

Water and Wastewater.com Help Forum - What does formaldehyde do to EPS?

Question by wilfred

What does formaldehyde do to EPS?

Whenever measuring EPS content, formaldehyde is always used for extraction. But so far i didn't figure out what function formaldehyde play in this extraction process.


Answer by Victor Santa Cruz

EPS, or the more technical term glycocalyx, is defined as that polysaccharide-containing material lying outside of the cell. The glycocalyx varies in composition and can include polyalcohols, different polysaccharides, as well as amino sugars. This said, formaldehyde is an electrophile and perhaps a strong carbocation with the C compounds present in the glycocalyx.

Answer

To be a suitable solvent this should fulfill two major goals

- having superior solubilizing properties (high uptake rate and capacity)
- solubilize other compounds as little as possible.

I never had the task to optimize this myself, however, some general points.

while glucose is highly soluble in water their is a range of other solvents with even better solvent properties, especially when solubilization of polymeric carbohydrates is the task.

Superior in this respect are polar organic solvents with high dipol momentum but lacking the ability of self association by hydrogen bond formation, namely
aldehydes (formaldehyde, glutaraldehyde), formamide, NMP (n-methyl pyrrolidone), DMSO (dimethyl sulfoxide). This solvents lead to optimal solvation of the carbohydrates by forming hydrogen bonds with the hydroxylgroups of these polymers.

Unfortunately, the aldehydes strongly denaturate proteins which also constitute a part of the EPS. By the same reason these are related to severe health risk. It is beyond my knowledge why DMSO or NMP are not used as more benign solvents.

For sure, a lot of researchers have dealt with the comparison of different extraction methods,
for example see http://www.iwaponline.com/wst/03907/wst039070211.htm.

Kind regards
T. Sobisch