Heterologous expression of anaerobic reductive dehalogenases: host nanoarchitectonics and synthetic biology...

Organohalide-respiring bacteria (OHRB) can efficiently degrade organohalides in anoxic environments. However, their application is limited by the slow growth rates, oxygen sensitivity, and substrate specificity. Heterologous expression of dehalogenases - the core catalytic components in robust hosts, such as Escherichia coli and Bacillus megaterium, has emerged as a transformative approach to overcome these limitations. This review summarizes current advances in the catalytic mechanisms and cofactor dependencies of reductive dehalogenases (RDases), with particular emphasis on cobalamin and iron-sulfur cluster requirements. The cobalamin salvage system exemplified by E. coli enables rapid protein production, but faces challenges related to exogenous cobalamin dependence and oxidative folding pathways. In contrast, hosts equipped with de novo cobalamin biosynthesis systems and secretion capabilities represent an advantageous yet underexplored alternative. To facilitate rational system design, a "host-enzyme-environment" evaluation framework is proposed to assess the heterologous expression of dehalogenases, emphasizing cofactor supply, stress resilience, and environmental adaptability. Additionally, future optimization directions are also outlined, including information mining at the genetic level, enzymatic modification, and the development of highly efficient degradation artificial systems using modified microorganisms. Overall, this review provides a comprehensive perspective on the current limitations and emerging solutions for heterologous expression, offering a foundation for the development of efficient and scalable biocatalytic systems for organohalide remediation.