Hormesis-Like Effects of Tetrabromobisphenol A on Anaerobic Digestion: Responses of Metabolic Activity and Microbial Community

Abstract

Tetrabromobisphenol A (TBBPA) has extensive applications in various fields; its release into ecosystems and the potential toxic effects on organisms are becoming major concerns. Here, we investigated the effects of TBBPA on anaerobic digestion, whose process is closely related to the carbon cycles under anaerobic conditions. The results revealed that TBBPA exhibited dose-dependent hormesis-like effects on methane production from glucose, i.e., the presence of 0.1 mg/L TBBPA increased the methane production rate by 8.79%, but 1.0−4.0 mg/L TBBPA caused 3.45−28.98% of decrement. We found that TBBPA was bound by the tyrosine-like proteins of the extracellular polymeric substances of anaerobes and induced the increase of reactive oxygen species, whose slight accumulation stimulated the metabolism activities but high accumulation increased the apoptosis of anaerobes. Owing to the differences between individual anaerobes in tolerance, TBBPA at 0.1 mg/L stimulated the acidogenesis and hydrogenotrophic methanogenesis, whereas higher levels (i.e., 1.0−4.0 mg/L) severely restrained all of the processes of acidogenesis, acetogenesis, and methanogenesis. Along with the accumulation of bisphenol A (BPA) produced from TBBPA by Longilinea sp. and Pseudomonas sp., the methanogenic pathway was partly shifted from acetate-dependent to hydrogen-dependent direction, and the activities of carbon monoxide dehydrogenase and acetyl-CoA decarbonylase/synthase were inhibited, while acetate kinase and F420 were hormetically affected. These findings elucidated the mechanism of anaerobic syntrophic consortium responses to TBBPA, supplementing the potential environmental risks of brominated flame retardants.

1-Butyl-3-methylimidazolium Chloride Affects Anaerobic Digestion through Altering Organics Transformation, Cell Viability, and Microbial Community

“…The pH in all the digesters was adjusted to 7.0 ± 0.1. After being stirred for 10 min, the digesters were flushed with N 2 for 5 min, sealed, and incubated in the air-bath shaker (35 ± 1 °C, 120 rpm) for 24 h. After the experiment, the mixtures were determined using three-dimensional excitation–emission matrix spectroscopy (EEM), ultraviolet–visible spectroscopy (UV–vis), and Fourier-transform infrared spectroscopy (FTIR), with the methods in accordance with published literature studies. , The fluorescence quenching process was quantitively analyzed by the Stern–Volmer equation (Supporting Information). …”

“…TS, VS, VFAs, carbohydrates, and proteins were estimated by the methods reported previously. − Methane and hydrogen were measured using a gas chromatograph (GC112A, China) based on the published literature studies . The membrane fluidity of microbial cells was analyzed via flow cytometry, with the analysis process being detailed in our previous studies. , An analysis of variance with least significant difference test was applied to evaluate the significance of results, and p < 0.05 was treated as statistically significant.…”

“…15,22 The composition of BA medium was designed according to the reference. 16,21 Then, BmimCl was injected into these digesters to obtain their predetermined concentrations (i.e., 0, 1, 5, 10, 15, and 20 mg/L). Among them, the digester without BmimCl addition was used as the control, while 1−20 mg/L was selected depending on the environmental levels.…”

“…30 The membrane fluidity of microbial cells was analyzed via flow cytometry, with the analysis process being detailed in our previous studies. 16,32 An analysis of variance with least significant difference test was applied to evaluate the significance of results, and p < 0.05 was treated as statistically significant.…”

“…It was reported that Rm and λ were closely related to microbial activity and acute toxicity, respectively. 16,18 Thus, the results presented above suggested that BmimCl inhibited anaerobic syntrophic consortia activity.…”