The HBCDs biodegradation using a Pseudomonas strain and its application in soil phytoremediation

Area of Science:

• Environmental Science
• Microbiology
• Biotechnology

Background:

• Hexabromocyclododecanes (HBCDs) are widely used brominated flame retardants with known adverse health effects.
• Limited information exists regarding the bacterial degradation pathways of HBCDs.
• HBCDs pose risks including inappropriate antidiuretic hormone syndrome and potential carcinogenicity.

Purpose of the Study:

• To isolate and characterize a bacterial strain capable of degrading HBCDs.
• To elucidate the metabolic pathways involved in HBCD degradation by the isolated strain.
• To evaluate the efficacy of the bacterial strain in the bioremediation of HBCD-contaminated soil and plants.

Main Methods:

• Isolation and identification of HBCD-degrading bacteria, specifically Pseudomonas aeruginosa HS9.
• Quantification of HBCD removal by strain HS9 over 14 days.
• Metabolite identification to determine degradation pathways, including debromination and hydroxylation.
• Bioremediation trials in soil and plant (maize) systems.
• Microbial diversity analysis using 16S rRNA gene sequencing.

Main Results:

• Pseudomonas aeruginosa HS9 effectively removed 69% of HBCDs in liquid culture within 14 days.
• Two distinct degradation pathways were identified: sequential debromination to cyclododecatriene derivatives and simultaneous debromination/hydroxylation yielding novel pentabromocyclododecanols.
• In soil bioremediation, strain HS9 reduced HBCDs by 87.6% (4.08 mg/g to 0.1 mg/g).
• In maize plants, HBCDs were reduced by 25% (0.1 mg/g).
• Application of strain HS9 promoted the abundance of beneficial soil bacteria.

Conclusions:

• Pseudomonas aeruginosa HS9 demonstrates significant potential for the bioremediation of HBCDs.
• The identified degradation pathways provide crucial insights into microbial metabolism of HBCDs.
• The study highlights the dual benefit of HBCD reduction and enhancement of beneficial microbial communities in contaminated soils.