Isolation ofPseudomonassp. Strain HB01 Which Degrades the Persistent Brominated Flame Retardant γ-Hexabromocyclododecane

Abstract

In this study, we isolated Pseudomonas sp. strain HB01 from a soil sample contaminated with brominated pollutants, and found that it degraded -hexabromocyclododecane (-HBCD). The strain degraded 81% of 1 mM -HBCD within 5 d of culture. Furthermore, it demonstrated biodegradation of structurally related (bromo) alkanes. To the best of our knowledge, this is the first report that outlines the isolation of a bacterial strain that degrades -HBCD.Key words: hexabromocyclododecane; brominated flame retardants; Pseudomonas; biodegradation; -HBCD Brominated flame retardants (BFRs) are routinely added to various consumer products to aid in the reduction of fire-related injury and property damage. Hexabromocyclododecane (HBCD) is an additive BFR present in extruded and expanded polystyrene foams (over 85% of total volume), and it forms a common component of the insulation materials used in the building and upholstery industries.1) Approximately 16,700 tons of HBCD were produced worldwide in 2001, and thus it is now identified as a high productionvolume chemical.2) Recently, a great deal of concern over risk of HBCD has arisen, as monitoring studies have demonstrated that HBCD pollution has expanded, and that residual levels in both the environment and vertebrates at higher levels in the food chain have increased over the last decade.3) Furthermore, several studies suggest toxic effects of HBCD on mammals. 2,3)In 2007, HBCD was defined as a persistent, bioaccumulative, and toxic (PBT) chemical. 4) Despite this, no suitable alternatives are presently available. Moreover, high concentrations of HBCD are also often detected in test samples, including sediment and fish that are collected within close proximity of production and handling sites.5) Thus the development of a microbial degradation system can be a solution to aid in the reduction of HBCD levels released into the environment. In the present study, we aimed to isolate a bacterial strain that is able to degrade HBCD.Technical HBCD consists of a mixture of three diastereomers, , and forms of 1,2,5,6,9,10-HBCD (Fig. 1).6) -HBCD forms the major component of the technical product (75-89%), while -HBCD and -HBCD are present in lower amounts (10-13% and 1-12% respectively).3) Hence we focused on -HBCD in this study. For screening of microorganisms that demonstrate potential -HBCD degradation activity, enrichment culture was performed as described previously, 7) with the exception of using 0.1% -HBCD (a kind gift from Manac Co., Ltd., Fukuyama, Japan) rather than 2,4,6-tribromophenol. For the culture of bacteria, a single colony was first inoculated into 10 ml of medium A (1.0 g of glucose, 5.0 g of polypeptone, 5.0 g of yeast extract, and 10 g of NaCl per liter, pH 7.0) in a 100-ml conical flask, after adding 100 ml of 100 mM -HBCD solution dissolved in dimethyl sulfoxide. The inoculants were then incubated by placing the flasks on a reciprocal shaker and shaking them at 150 rpm at 28 C, and -HBCD was recovered by ether extraction, as described previously.7) For rapid analys...

Study of novel pure culture HBCD-1, effectively degrading Hexabromocyclododecane, isolated from an anaerobic reactor

“…A strain of Pseudomonas sp. has been reported that it degraded 81% of 1 mM c-HBCD within 5 days treatment (Yamada et al, 2009). However, in this study, a pure culture of Achromobacter sp.…”

Debromination of Hexabromocyclododecane by Anaerobic Consortium and Characterization of Functional Bacteria

“…The dibromocyclododecadiene (DBCD, 322 m/z), a typical debromination product, was detected using UHPLC/Q-TOF-MS during reactive process (Supplementary Figure S1 ). Comparison of HBCD biodegradation and bromide generation, it could be deducted that bromide released from HBCD reduction by debromination process, which was consistent to the previous reports ( Yamada et al, 2009 ). Transformation and correlation of VSS and TOC indicated that on the one hand, during 12 days cultivation, microbial growth experienced lag phase, log phase, and stationary phase, sequentially ( Figure 2F ; Fang and Jia, 1999 ); on the other hand, the biodegradation process with the generation of bromide was significantly negative correlated with the TOC analysis.…”

“…The previous report about the acclimation of microbial communities to mineralize the organic compounds indicated that some of enriched microorganism may be utilized to degrade the treated hazardous materials ( Xiao and Roberts, 2013 ). Based on this, it can be speculated that the microbial enriched during the HBCD acclimated process may have a potential capability of degrading HBCD, just like Pseudomonas , which has been described previously ( Yamada et al, 2009 ).…”

“…To date, microorganisms have been reported to degrade HBCD both in aerobic and anaerobic conditions, such as Pseudomonas sp. Strain HB01, isolated from soil, can remove 81% of 1 mM γ-HBCD within 5 days of culture ( Yamada et al, 2009 ). Under the anaerobic condition, a broken-down of technical HBCD mixture has been reported, (±)-a-HBCD exhibited an almost doubled half-life compared to (±)-β-HBCD and (±)-γ-HBCD ( Davis et al, 2004 ; Gerecke et al, 2006 ).…”

Microbial Degradation of Some Halogenated Compounds: Biochemical and Molecular Features

“…HB01 [45]. Since bromide atom was not detected after degradation reaction, such transformation might not through haloelimination.…”