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Updated: Jun 12, 2026

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
Published on: October 7, 2020
Anaerobic testosterone degradation in Steroidobacter denitrificans--identification of transformation products
Michael Fahrbach1, Martin Krauss, Alfred Preiss
1Eawag, Swiss Federal Institute of Aquatic Science and Technology, Uberlandstrasse 133, CH-8600 Dübendorf, Switzerland. michael.fahrbach@web.de
Abstract:
The transformation of the androgenic steroid testosterone by gammaproteobacterium Steroidobacter denitrificans was studied under denitrifying conditions. For the first time, growth experiments showed that testosterone was mineralized under consumption of nitrate and concurrent biomass production. Experiments with cell suspensions using [4-(14)C]-testosterone revealed the intermediate production of several transformation products (TPs). Characterisation of ten TPs was carried out by means of HPLC coupled to high resolution mass spectrometry with atmospheric pressure chemical ionization as well as (1)H and (13)C NMR spectroscopy. 3beta-hydroxy-5alpha-androstan-17-one (trans-androsterone) was formed in the highest amount followed by 5alpha-androstan-3,17-dione. The data suggests that several dehydrogenation and hydrogenation processes take place concurrently in ring A and D because no consistent time-resolved pattern of TP peaks was observed and assays using 2 TPs as substrates resulted in essentially the same TPs. The further transformation of testosterone in S. denitrificans seems to be very efficient and fast without formation of detectable intermediates.
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