Untitled

Abstract

Tetrabromobisphenol-A is a reactive flame retardant used in the production of many plastic polymers. In previous research, it was demonstrated that anaerobic microorganisms from contaminated sediment debrominate tetrabromobisphenol-A to bisphenol-A, but an enrichment culture was not established. The current study was carried out to identify the intermediate metabolites in this process and to determine the factors facilitating enrichment of debrominating microorganisms. During the enrichment process in an anaerobic semi-continuous batch reactor, tetrabromobisphenol-A debromination gradually slowed down with concurrent accumulation of three intermediate products. These compounds were tentatively identified using GC-MS as tri-, di-, and mono-brominated bisphenol-A. GC-MS and HPLC analyses showed one dominant metabolite of dibromobisphenol-A, and NMR analysis identified it as 2,2'-dibromobisphenol-A. Addition of sterile sediment (15% wt/wt) to the reactor stimulated debromination of tetrabromobisphenol-A. Furthermore, different solid amendments such as surface soil and pulverized gray chalk from the site subsurface (100 m below ground) were also stimulating agents. We conclude that organic matter is involved in stimulation since the stimulation effect of the sediment, soil and gray chalk was abolished after it was heat-treated to 550 degrees C. Our study suggests that the debrominating culture requires some organic components found in the sediment, soil, and chalk in order to sustain activity and perhaps to survive. The possible mechanisms of stimulation by these solids are discussed.

Biochar and activated carbon act as promising amendments for promoting the microbial debromination of tetrabromobisphenol A

“…1). Only one diBBPA isomer (3,3′-diBBPA) was detected, supporting the premise that biological reductive dehalogenation of TBBPA is position-dependent, as previously proposed in Arbeli and Ronen (2003). Indeed, if debromination of the three bromines on 3,3′,5-triBBPA was equally favorable, we would expect the proportion of 3,3′-diBBPA to be 50% of the two dibrominated BPA isomers.…”

“…No further BPA degradation occurred in the biotic reactors. This finding is not surprising as BPA accumulation has been commonly observed under anoxic conditions (Arbeli and Ronen, 2003; Chang et al, 2012; Liu et al, 2013; Lefevre et al, 2016), and is attributed to the presence of a methylene linker joining the two BPA molecule aromatic rings, preventing their cleavage by anaerobic microorganisms (Chang et al, 2012). Yet, anaerobic biotransformation of TBBPA to BPA ultimately brings the TBBPA degradation process closer to complete mineralization, since subsequent mineralization of BPA can rapidly occur if aerobic conditions are provided, thus making the contaminant well-suited to a two-stage treatment process (Liu et al, 2013).…”

“…Our previous study (Lefevre et al, 2016), which used the same reactor settings without the addition of carbonaceous materials, showed a similar distribution of TBBPA by-products to that presently observed in the control reactor. A transient accumulation of the dihalogenated congener during the microbial reductive debromination of TBBPA, or even TCBPA (tetrachlorobisphenol A), has been previously reported in the literature (Arbeli and Ronen, 2003; Chang et al, 2012; Sun et al, 2014). These observations suggest that the transformation of 3,3′-diBBPA to 3-monoBBPA may be the limiting step of TBBPA reductive debromination.…”

“…These observations suggest that the transformation of 3,3′-diBBPA to 3-monoBBPA may be the limiting step of TBBPA reductive debromination. A possible explanation for this finding is that the presence of an unequal number of halogens on each phenolic ring creates a stronger positive dipole moment of the tri- and monoBBPA molecules, which makes them more susceptible to undergo nucleophilic attack compared to diBBPA (Arbeli and Ronen, 2003). Thus, mono- and triBBPA are in theory more easily debrominated compared to diBBPA.…”

Tetrabromobisphenol A – Toxicity, environmental and occupational exposures

“…Badania eksperymentalne nad moż-liwością mikrobiologicznej degradacji TBBPA w osadach w warunkach ograniczonej dostępności tlenu sugerują, że TBBPA może ulegać całkowitej dehalogenacji do bisfenolu A, a następnie procesom mineralizacji w warunkach tlenowych. Dodatkowo w badaniu tym oznaczono produkty metabolizmu TBBPA, takie jak monobromobisfenol A, dibromobisfenol A i tribromobisfenol A [42].…”