Isolation and Characterization of a Novel Diethylstilbestrol-Degrading Bacillus subtilis JF and Biochemical Degradation Metabolite Analysis.

Weiqin Deng,Shuliang Liu,Shujuan Chen,Xinjie Hu,Yong Yang,Kaidi Hu,Xiaolin Ao,Li He,Likou Zou,Yun Zhao

doi:10.3389/fmicb.2019.02538

Abstract

Diethylstilbestrol (DES) can adversely affect the immune system of developing fetuses or even elicit toxic responses such as nerve toxicity and genotoxicity in human beings, thereby warranting methods to remove DES from the environments. The present study characterized a novel DES-degrading Bacillus subtilis JF and analyzed the degradation metabolites. The strain was collected at the China General Microbiological Culture Collection Center (Collection number: CGMCC 7950). The environmental effects, such as DES concentrations, pH levels, and temperature, on the strain’s degradation ability were tested. Degradation metabolites of DES by strain JF were analyzed via high performance liquid chromatography (HPLC) and liquid-chromatography time of flight mass spectrometry (LC-TOF-MS). Results indicated that B. subtilis JF can effectively degrade DES within a concentration of 25–200 mg/L. Increasing pH levels (pH > 7) are reported to increase the degradation rate of DES by the strain. The optimal temperature for strain JF to degrade DES was identified as 45°C. In this study, 4, 4′-hexene estrogen quinones (DESQ) and DES-4-semiquinone were speculated as two degradation metabolites of DES, and both can be completely degraded by strain JF. A slight reduction of DES in the blank system [DES cultured in Luria-Bertani (LB) medium without strain JF] was observed in this study. The reduction trend in the blank system only occurred during the first few days (about 4 days) and was considerably lesser than the decomposition and transformation effect of DES via strain JF. Furthermore, the metabolite DESQ could not be further decomposed in blank LB medium without strain JF. All the results demonstrate that complete degradation of DES in the fermentation broth occurs due to the function of strain JF rather than organic decomposition. In conclusion, the high efficiency of degradation and the potential to degrade DES completely indicates that strain JF has potential for the bioremediation of DES-contaminated environments (soil, river, and so on) and fermented foods.

Highlights

Diethylstilbestrol (DES) is a synthetic non-steroidal estrogen, previously used to prevent habitual abortion in pregnant women from 1940 to 1970 in the United States
Few studies reported that DES can improve the growth rate of animals and increase the protein content as it was once used to promote growth in livestock and aquaculture (Du and Xu, 2000; Liu et al, 2008); subsequent researches identified that the accumulation of DES in animal products such as liver, eggs, and milk, which are consumed by expectant mothers, may lead to crucial endocrine disorders and obesity in the offspring (Newbold et al, 2009)
The result is similar to the results of DES degradation ability of JF inoculated in Mineral salt medium (MSM) medium; the residual DES in blank group and treatment group is 1.654 and 1.639 mg/L, respectively

Summary

Introduction

Diethylstilbestrol (DES) is a synthetic non-steroidal estrogen, previously used to prevent habitual abortion in pregnant women from 1940 to 1970 in the United States. Despite its positive effect in preventing habitual abortion or even premature birth in expectant mothers, further research revealed that there would be higher incidence of abortion and premature birth when women were exposed to DES (Dieckmann et al, 1953; Brackbill and Berendes, 1978). Few studies reported that DES can improve the growth rate of animals and increase the protein content as it was once used to promote growth in livestock and aquaculture (Du and Xu, 2000; Liu et al, 2008); subsequent researches identified that the accumulation of DES in animal products such as liver, eggs, and milk, which are consumed by expectant mothers, may lead to crucial endocrine disorders and obesity in the offspring (Newbold et al, 2009). DES has gained immense social attention, and several countries have banned the use of DES as a growth promoter due to its toxic effects (Judson et al, 2009)

Methods

Results

Discussion

Conclusion