Bacterial laccases for green remediation of contaminants of emerging concern: from molecular cloning to metagenomic and computational insights.

Contaminants of emerging concern (CECs) are increasingly recognized for their persistence, widespread occurrence, and potential risks to environmental and human health. Their frequent detection in wastewater, surface water, drinking water, and food chains underscores the urgent need for sustainable remediation strategies. Laccases, versatile multicopper oxidases, have demonstrated strong potential for degrading organic pollutants through oxidative mechanisms that transform complex contaminants into less toxic products. While fungal laccases have been extensively studied, bacterial laccases are gaining attention due to their structural simplicity, stability under alkaline conditions (pH 7.5-9.0), and limited requirement for post translational modifications. Recent studies indicate that bacterial laccases can transform approximately 60-80% of industrial dyes, a major class of CECs, even in complex wastewater matrices. Despite notable progress, broader application of bacterial laccases remains constrained by limited enzyme stability under industrial operating conditions, reduced catalytic performance under high salinity, extreme pH, and mixed pollutant environments, and frequent dependence on costly redox mediators, highlighting the need for more robust enzymes and sustainable mediator alternatives. This review summarizes recent advances in bacterial laccase research, with emphasis on structural and substrate specific insights, molecular cloning, heterologous expression, and optimized purification strategies. It also highlights emerging approaches such as metagenomics and machine learning for identifying robust, thermostable, and alkali resistant bacterial laccases suitable for large scale applications. Collectively, these advances support green chemistry principles and contribute to multiple United Nations Sustainable Development Goals by enhancing wastewater treatment efficiency, reducing energy and chemical inputs, and promoting sustainable waste valorization.