Effluent decontamination by the ibuprofen-mineralizing strain, Sphingopyxis granuli RW412: Metabolic processes

Area of Science:

• Environmental Microbiology
• Bioremediation
• Pharmaceutical Pollution Control

Background:

• Ibuprofen is a widely used pharmaceutical pollutant detected in aquatic systems due to incomplete removal by conventional wastewater treatment plants (WWTPs).
• The environmental and public health risks associated with emerging contaminants like ibuprofen necessitate advanced treatment technologies.
• Biopurification systems utilizing contaminant-degrading bacteria offer a sustainable and cost-effective approach for water decontamination.

Purpose of the Study:

• To isolate, characterize, and evaluate an ibuprofen-mineralizing bacterial strain for its efficacy in remediating ibuprofen-polluted environments.
• To elucidate the genetic and enzymatic pathways involved in ibuprofen biodegradation by the identified bacterial strain.
• To assess the strain's performance in various matrices, including laboratory media, biopurification systems, and real WWTP effluent.

Main Methods:

• Isolation and identification of ibuprofen-degrading bacteria from environmental samples (River Elbe sediments).
• Genomic analysis of the isolated strain (RW412, identified as Sphingopyxis granuli) to identify key biodegradation genes (ipf genes).
• Enzymatic assays to confirm the function of ipf genes in ibuprofen mineralization pathway.
• Microbial degradation experiments in liquid cultures, biopurification systems, and spiked WWTP effluent.

Main Results:

• Strain RW412 (Sphingopyxis granuli) possesses a 4.48 Mb genome with plasmids containing ipf genes responsible for initiating ibuprofen mineralization.
• The identified enzymes catalyze CoA ligation, aromatic ring activation, and retroaldol cleavage, producing intermediates for further degradation.
• Strain RW412 efficiently eliminated over 2 mM ibuprofen in 74 hours in lab conditions and rapidly remediated repeated doses in biopurification systems.
• The strain prevented metabolite accumulation and demonstrated a 7-fold faster ibuprofen removal rate in WWTP effluent compared to indigenous microbiota.

Conclusions:

• Sphingopyxis granuli RW412 is a robust bacterium capable of effectively mineralizing ibuprofen under diverse conditions.
• The identified ipf genes and their encoded enzymes provide a mechanistic understanding of ibuprofen biodegradation.
• This bacterial strain represents a promising bio-augmentation tool for enhancing ibuprofen removal efficiency in urban wastewater treatment systems, mitigating environmental contamination.