Microbial dehalogenation: A critical review on the detoxification paradox and the steering of metabolic pathways

Microbial dehalogenation plays an important role in tackling the global environmental concern of halogenated organic pollutant (HOP) contamination. While traditionally thought to be a detoxifying process, microbial dehalogenation is now reevaluated due to complex metabolism which may generate toxic intermediates. The accumulation of transient, hydrophilic, and sometimes more toxic metabolites can be a serious threat to ecosystems and human health. This review discusses the recent advances regarding the formation, fate, and ecotoxicological effects of dehalogenation intermediates under anaerobic and aerobic conditions. Key factors including microbial community structures, enzyme specificity and physicochemical parameters contributing to the divergence between complete mineralization and partial dehalogenation are discussed. In addition, we highlight innovative approaches capable of redirecting the metabolic flux of microbes away from detrimental pathways, including biomolecular engineering of dehalogenases, rational construction of synthetic microbial consortia and integrated biotic–abiotic systems. This review establishes a transformative framework to advance bioremediation from an empirically driven practice to a precisely targeted technology, paving the way for unequivocal detoxification of HOPs.