Naproxen as an emerging environmental contaminant: Microbial degradation mechanism and optimization strategies

Naproxen, a non-steroidal anti-inflammatory drug (NSAID), has emerged as a contaminant of concern due to its environmental persistence, incomplete removal by conventional wastewater treatment processes, and associated ecological risks. It has been detected at concentrations ranging from nanograms to micrograms per liter in surface waters, wastewater effluents, and, in some cases, drinking water, particularly in regions with limited treatment infrastructure. Several bacterial genera, such as Pseudomonas and Bacillus, have been reported to transform naproxen through hydroxylation and ring-modification reactions catalyzed by specific enzymes. Microbial consortia, when provided with optimal pH, temperature, oxygen, and nutrient conditions, demonstrate greater degradation efficiency compared to single strains. Despite extensive research on pharmaceutical pollution, a comprehensive understanding of naproxen biodegradation and the environmental factors influencing its removal remains limited. This review synthesizes current knowledge on the occurrence of naproxen in aquatic environments, microbial degradation pathways, and the influence of the combined effects of microbial characteristics and abiotic parameters, including pH, temperature, oxygen availability, and nutrient supply, on degradation efficiency. Several key knowledge gaps remain, including an incomplete understanding of metabolic pathways utilized by diverse microbial communities, the impact of emerging contaminants on naproxen degradation, and the long-term ecological implications of residual naproxen in treated effluents. In addition, challenges related to scaling laboratory findings to real-world applications and integrating biodegradation with other treatment technologies require further investigation. By integrating dispersed findings into a unified conceptual framework, this review identifies critical knowledge gaps and proposes future research directions to advance biologically based strategies for pharmaceutical wastewater treatment.