Monitoring estrogen and androgen residues from livestock farms in Phayao Lake, Thailand.

The aim of the present study was to investigate steroid hormone residues from livestock farms and assess their risks to the surface water of Phayao Lake. These steroid hormones are endocrine-disrupting compounds (EDCs), which can be found in natural and synthetic forms. This research focused on examining the residues of seven steroid hormones (five estrogens and two androgens-estrone (E1), 17α-estradiol (αE2), 17ß-estradiol (ßE2), estriol (E3), 17α-ethinyl estradiol (EE2), testosterone (T), and 17α-methyltestosterone (MT)) from four types of livestock farms around Phayao Lake, Thailand. The samples collected from the livestock farms included feces, soil, and wastewater and were extracted by the solid phase extraction (SPE) technique and analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). The risks from the residual steroid hormones were also characterized by estradiol equivalents (EEQs), testosterone equivalents (TEQs), and risk quotients (RQs). The results indicated that most hormone contamination from the farms' livestock was due to the estrogen hormones E1 (1.38-97.10 ng/g), ßE2 (10.08-1366 ng/g), and EE2 (1.50-99.92 ng/g), which originate from the natural excretion and admixture of steroids in feedstock or medicines. Steroid hormones were not detected in the wastewater from cleaning processes on farms with wastewater treatment plants, whereas farms without wastewater treatment plants showed high values of estrogen hormone contamination, with EEQs of 128.8-472.9 ng/L and RQs of 208.3-294.3. However, the analysis of steroid hormone residues in Phayao Lake demonstrated that the residues did not severely affect aquatic organisms (with RQs of 0.002-144.5), and no estrogen or androgen residues were observed in the water treatment plant or tap water.

Degradation of 17α-methyltestosterone by Rhodococcus sp. and Nocardioides sp. isolated from a masculinizing pond of Nile tilapia fry.

17α-Methyltestosterone (MT), a synthetic anabolic androgenic steroid, is widely used in aquafarming for the production of an all male fish population such as Nile tilapia. This study isolated, identified and characterized MT-degrading bacteria in the sediment and water from a masculinizing pond of Nile tilapia fry. Based on the phylogeny, physiological properties and cell morphology, the three isolated MT-degrading bacteria were related closely to Rhodococcus equi, Nocardioides aromaticivorans, and Nocardioides nitrophenolicus. Growth of the three isolated strains was found to be inhibited for MT concentrations in the range of 1.0-10mg/L. The inhibition of cell growth was found to be modeled using the Haldane's substrate inhibition model. The kinetic constants ranged from 0.13 to 0.19h(-1) for µ(max), 0.7-24.8mg/L for K(s) and 19.6-76.2mg/L for K(i). Androgenic activity using ß-galactosidase assay showed that all strains degraded MT to the products with no androgenic potency.

Biotransformation of 17α-methyltestosterone in sediment under different electron acceptor conditions.

17α-Methyltestosterone (MT), an anabolic androgenic steroid, is used widely in inducing an all male population in aquaculture farming of fish, such as Nile tilapia (Oreochromis niloticus). Current understanding of the occurrence and fate of MT in the sediments and the surrounding areas of the aquaculture ponds are very limited. Bioassay tests showed that MT was biotransformed under aerobic and sulfate-reducing conditions with a half-life of 3.8d and 5.3d, respectively, with complete disappearance of androgenic activity. However, under methanogenic condition, MT was found to biotransform but the androgenic activity continued to persist even after 45 d of incubation. In contrast, MT was found to transform slowly under iron(III)-reducing condition and was hardly transformed under nitrate-reducing condition. A possible reason for the lack of transformation of MT under nitrate-reducing condition is the presence of the methyl group at the C-17 position. The results of this study suggest that MT and its degradation products with androgenic activity may potentially accumulate in the sediments of fish farming ponds under iron(III)-reducing, nitrate-reducing and methanogenic conditions.

Biodegradation of 17alpha-methyltestosterone and isolation of MT-degrading bacterium from sediment of Nile tilapia masculinization pond.

The fast growing and highly tolerant fish Nile tilapia is one of the most commonly raised fish in the aquaculture industry. To produce an all-male population, a common practice is to feed the Nile tilapia fry with 17alpha-methyltestosterone (MT)-impregnated food. Uneaten fish food with MT may accumulate in the masculinization ponds and be released into the receiving waters. Not much is known about the fate of MT in the fish farms and in the receiving streams. The objective of this study is to investigate the biodegradation of MT under aerobic condition and to isolate responsible microorganisms. Aerobic biodegradation tests were conducted with MT concentrations of 0.3, 1.0, 5.0, 7.0, and 10.0 mg/L using sediment from the masculinization pond as microbial seed. The results suggested that MT is biodegradable. Lag phase was not observed in all cases. With initial concentrations of 0.3, 1.0, 5.0, 7.0, and 10.0 mg/l, the first-order degradation rates were 0.52, 0.23, 0.17, 0.13 and 0.10 day(-1), respectively. Degradation rates were found to decrease with an increase in the initial MT concentration. Analysis of 16S rRNA gene sequences of a strain isolated from the sediment indicated that the strain was highly similar to Pimelobacter simplex strain S151 (100%) which is in the genus Nocardioidaceae. Using this strain, MT is degraded with a first-order degradation rate of 0.044 h(-1) excluding the lag phase. This is the first work reporting biodegradation of MT and isolation of MT-degrading bacterium from environment.