Conventional methods of filtering waste water in sewage treatment plants are unable to completely remove medicine residues such as the estrogens in birth control pills. These residues then find their way into rivers and lakes and also accumulate in our drinking water. For fish and other aquatic life, estrogens can lead to reproductive and developmental disorders and even to the formation of female characteristics in males. The potential long-term consequences for human beings -- declining sperm counts, infertility, various cancers, and osteoporosis -- are still largely unknown.

Students from the Bielefeld University's Center for Biotechnology have now developed a biological filter in which specific enzymes (so-called laccases) break down these medicine residues. One known source of particularly efficient laccases is the turkey tail, a type of fungus that grows on trees. Using methods from synthetic biology, the students succeeded in synthesizing this enzyme and applying it to filter material.

'We didn't want to invent something totally crazy with our project -- just because it's technically feasible. We wanted to do something that could actually be put to use in the near future, perhaps in 20 years, and be a real benefit', explains Robert Braun, a master student of molecular biotechnology. 'The biofilter is such a project. And we have shown that our idea works. In principle, a company could now come along and develop our filter further. We ourselves have got to get back to our studies -- most of us have rather neglected them for the last 6 months. However, the experiences we have gathered more than compensate for that'.