Why does my water smell like mold

15.11.2007 11:11

Scruffy, earthy, musty: bacteria cause repulsive smells in fish and drinking water

Dr. Elisabeth Hoffmann Press and public relations
Technical University Carolo-Wilhelmina in Braunschweig

Researchers at the TU Braunschweig decipher the biosynthesis of methyl isoborneol

Sometimes it smells like fresh earth, sometimes scruffy, musty and unpleasant: methyl isoborneol. In addition to the soil, the substance can also accumulate in drinking water and fish. Even in the smallest concentrations of only ten nanograms per liter, our noses can smell it. The chemical compound is produced exclusively by bacteria. Now the working group of Prof. Stefan Schulz at the Institute for Organic Chemistry at the Technical University of Braunschweig has demonstrated for the first time how the microorganisms produce the fragrance ("Biosynthesis of the off-flavor 2-Methylisoborneol by the Myxobacterium Nannocystis exedens" in: Angewandte Chemie 2007, 119, pp. 8436-8439 (German) and Angewandte Chemie International Edition 2007, 46 pp. 8287-8290 (English)).

This substance is not harmful to humans. But almost everyone finds their odor in connection with drinking water extremely unpleasant and off-putting. Even fresh water is considered inedible as soon as the methyl isoborneol is noticed in it. Utility companies therefore remove this at great expense when treating drinking water. The volatile substance can also accumulate in fish, which is then considered inedible due to the typical "sludge aroma". The food industry is accordingly interested in research results.

On the basis of the results that the Institute for Organic Chemistry has developed together with scientists at the Helmholtz Center for Infection Research in Braunschweig and at the University of Saarbr├╝cken, researchers can now search for the genes that are responsible for the synthesis of methylisoborneol, and later for example, inhibit the corresponding production mechanisms in the bacteria involved.

In search of the meaning of smells and aromas

In addition to these possible applications, chemists are fundamentally interested in the biosynthesis of aromas. "We want to know exactly why bacteria produce odors," explains Schulz. "Who thinks of bacteria when they enjoy a good cheese and a glass of red wine, when they carry out the stinking organic waste or when they get that earthy smell of methylisoborneol while walking? All these smells and aromas are produced by bacteria do they meet in nature and how have the taste and smell receptors in humans adjusted to them in the course of evolution? " How and why flavors are created has so far only been researched in areas of the food industry. Schulz's vision is to map all the fragrances produced by bacteria and to research their function in the interaction between living things.

He developed a hypothesis for the unpleasant effects of methyl isoborneol on humans. "Obviously the smell in connection with everything we want to eat and drink scares us off so vehemently because it sends out a drastic warning signal. But what is the point of this warning if the substance is harmless in itself?" asks Schulz. "Interestingly, some of the bacteria that also produce methyl isoborneol simultaneously produce highly toxic substances for humans. Cyanobacteria, also known as blue-green algae and found in standing water, can produce very dangerous toxins that cannot be smelled Over the course of evolution learned to interpret the penetrating smell as a warning signal for this danger. "

Prof. Dr. Stefan Schulz
Technical University of Braunschweig
Institute for Organic Chemistry
Hagenring 30
38106 Braunschweig
Tel .: +49 531 / 391-5271
Fax: +49 531 / 391-5272
Email: [email protected]

Features of this press release:
Biology, chemistry, information technology, sea / climate, environment / ecology
Research results, research projects