## 3 Microbiological Degradation of EDCs
Figure 3: HIP degradation pathway; HIP--9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid; HIP-CoA--9,17-dioxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid CoA ester; 9 OH-HIP-CoA--9-hydroxy-17-oxo-1,2,3,4,10,19-hexanorandrostan-5-oic acid CoA ester; HIP-CoA--9-hydroxy-17-oxo-1,2,3,4,10,19-hexanorandrost-6-en-5-oic acid CoA ester; 7,9 OH-HIP-CoA--7,9-dihydroxy-17-oxo-1,2,3,4,10,19-hexanorandrost-6-en-5-oic acid CoA ester; 7-oxo-9 OH-HIP-CoA--7-oxo-9-hydroxy-17-oxo-1,2,3,4,10,19-hexanorandrost-6-en-5-oic acid CoA ester; 9 OH-HIP-CoA--9-hydroxy-17-oxo-1,2,3,4,5,6,10,19-octanorandrostan-7-oic acid CoA ester; 9-oxo-HIC-CoA--9-oxo-17-oxo-1,2,3,4,5,6,10,19-octanorandrostan-7-oic acid CoA ester; 9-oxo-HIC-CoA--9-oxo-17-oxo-1,2,3,4,5,6,10,19-octanorandrostan-7-oic acid CoA ester; 9,17-dioxo-1,2,3,4,5,6,10,19-octanorandrost-8(14)-en-7-oic acid CoA ester; COCHEA-CoA--9-oxo-1,2,3,4,5,10,19-octanor-13,17-secoandrost-8(14)-ene-7,17-dioic acid CoA ester [9; 53]. A similar pathway has been characterized for progesterone degradation. This compound may be transformed to testosterone after a side-chain breakdown. Moreover, progesterone may undergo hydroxylation, hydrogenation and dehydrogenation to 3\(\beta\)-hydroxy-5\(\alpha\)-pregnant-20-one, 3,20-allo-preganedione and 1,4-pregnadiene-3,20-dione, respectively. These compounds were earlier observed during progesterone transformation by microalgae [55]. [PERSON] et al. [55] also observed the cleavage of the progesterone B ring between C9-C10 to 1-acetyl-4-[2-(5-hydroxy-2-methyl-phenyl)ethyl]-7\(\alpha\)-methyl-octahydro-1\(H\)-inden-5-one (Figure 5). Testosterone can also be degraded under anaerobic/anoxic conditions by denitrifiers, including _Steroidobacter denitrificans_, _Sterolibacterium denitrificans_ and _Thuera terenica_. Denitrification of the strain _Steroidobacter denitrificans_ oxidized testosterone to 1-dehydrotostosterone and probably also to androst-4-en-3,17-dione under anoxic condition. The NAD\({}^{+}\)-dependent enzyme, responsible for testosterone dehydrogenation is probably similar to 17\(\beta\)-hydroxysteroid dehydrogenases. The compounds obtained are then transformed to androsta-1,4-diene-3,17-dione. This pathway is similar to the testosterone degradation 9,10-seco pathway in aerobic conditions observed in _Comamonas testosterone_, however, due to the lack of oxygen there is no cleavage of the ring with the participation of dioxygenases [56]. However, androgens may also be degraded through the oxygenase-independent 2,3-seco pathway. The key intermediate in this pathway is 1-testosterone, which is dehydrogenated to 1,17-dihydroxy-androstan-3-one and in the next step to 17-hydroxy-androstan-1,3-dione. This compound is probably cleaved to 17-hydroxy-1-oxo-2,3-seco-androstan-3-oic acid (2,3-SAOA). The carboxylic group of 2,3-SAOA at position C-3 is activated by CoA. The C2 side chain at position C-5 of the activated compound is removed via retro-aldol reaction. The aliphatic chain of this compound is degraded by reactions analogous to \(\beta\)-oxidation (Figure 6) [28; 51; 53; 57]. Microalgae remove hormones through three mechanisms--bioadsorption, bioaccumulation and biodegradation/biotransformation. The ability of microalgae to accumulate pollution is related to their cell volume and surface area. In addition, the efficiency of endocrine substance adsorption on cell surfaces depends on the type of hormones. It was shown that more degradation-resistant diethylstilbestrol is easily adsorbed compared to 17\(\beta\)-estradiol. Despite the ability to adsorb and accumulate in the wall of the microalgae, it appears that the main process for hormone removal is biotransformation/b biodegradation [11; 26]. Enzymes such as peroxidase, glutathione S-transferase and cytochrome P450 are mainly involved in the biotransformation processes of these compounds [11]. Figure 5: Proposed progesterone biotransformation by algae [55]. [PERSON] et al.