## 3 Microbiological Degradation of EDCs
In addition, hydroxylation at position 4 of the 17\(\beta\)-estradiol ring and conversion of 4-hydroxy-17\(\beta\)-estradiol to 4-hydroxyestrone were also observed [10; 50]. [PERSON] et al. [37] described 17\(\beta\)-estradiol degradation by a mixed culture of _Rhodococcus equi_ DSSKP-R-001 and _Comomonas testosterone_ QYY20150409 and by individual strain. These authors showed that each strain degrades the hormone in a different pathway. 17\(\beta\)-estradiol degradation with the use of the strain QYY20150409 led through 2,6-dihydroxy-8-(7\(\alpha\)-methyl-1,5-dioxocotadhy-inden-4-yl)-7-oxoocata-2,4-dienoic acid to succinic acid and 3-(7\(\alpha\)-methyl-1,5-dioxocotadhy-1H-inden-4-yl)propanal. The strain DSSKP-R-001 degraded 17\(\beta\)-estradiol to 5-hydroxyhex-2-endioic acid. During the degradation of 17\(\beta\)-estradiol by the mixture of strains the new intermediates pent-4-enol; 3-(1,5-dihydroxy-7\(\alpha\)-methyl-octahydro-inden-4-yl)-propionic acid and 13-ethyl-3,4,16-trihydroxy-6,7,8,9,11,12,13,14,15,16-decahydro-17H-cyclopenta[\(\alpha\)] phenanthne-17-one appeared. Cooperation of the strains allowed 17\(\beta\)-estradiol to break down into non-aromatic products. The mechanisms of estrogen degradation by bacteria are shown in Figures 2 and 3. [PERSON] et al. [51] described the estradiol degradation strategy that is based on the conversion of estrogens to androgens and the subsequent degradation by the anaerobic 2,3-seco pathway. _Denitrations_ sp. strain DHT3 converts estrogens into androgens through the cobalamin-dependent methylation of estrogen, including the formation of a nucleophilic carboanion at C-10 on the phenolic A-ring. Androgenic intermediates are catabolized to 9,17-diox-1,2,3,4,10,19-hexanorandrostan-5-oic acid (HIP) [51; 52]. The _Comanonas testosteronei_ strain not only shows the ability to degrade estrogen derivatives, but also testosterone by the 9,10-seco pathway. The first step of testosterone degradation by this pathway is the dehydrogenation of the 17\(\beta\)-hydroxyl group to androst-4-en-3,17-dione, which is converted to androsta-1,4-diene-3,17-dione. The degradation of the sterane ring begins with the introduction of a hydroxyl group at position 9 of the aromatic ring, which leads to the formation of an unstable intermediate. As a result of the B ring cleavage and aromatization of the A ring of this compound, a secosterol (3-hydroxy-9,10-seco-androsta-1,3,5(10)-triene-9,17-dione) is formed. Further degradation steps include hydroxylation of the A ring in position 4 and its cleavage by 3,4-dioxygenase to 4,5-9,10-diseco-3-hydroxy-5,9,17-trioxoandrosta-1(10),2-diene-4-oic acid (4,9-DHSA) [27]. These compounds may undergo decomposition to  
Figure 2: Estrogens biodegradation by bacteria; the 4,5-seco pathway reactions are shown in blue; HIP–9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid [10; 12; 21; 25; 50]. 2-Hydroxyhexa-2,4-dienoate, and next to compounds incorporated into the central metabolism. Moreover, 4,9-DHSA may be also transformed to HIP. The degradation of this last one leads to the cleavage of both aromatic rings and, as a consequence, to the forming of propionyl-CoA and succinyl-CoA [9; 54]. The degradation pathway of testosterone by the _Comamonas testosterone_ strain is shown in Figure 4.  
Figure 4: Testosterone biodegradation by bacteria in aerobic conditions; 3-HSA–3-hydroxy-9,19-seco-androsta-1,3,5(10)-triene-9,17-dione; 3,4-DHSA-3,4-dihydroxy-9,10-seco-androsta-1,3,5(10)-triene-9,17-dione; 4,9-DHSA-3-hydroxy-5,9,17-trioxo-4,5-9,10-diseco-androsta-1(10),2-diene-4-oic acid; HIP degradation pathway; HIP–9,17-dioxo-1,2,3,4,10,19-hexanorandrosta-5-oic acid [9; 53; 54].