Engineering the microbial architects: a genetic revolution in bio-electrochemical hydrogen production.

Microorganisms, endowed with extraordinary metabolic versatility and environmental adaptability, represent a transformative frontier for addressing global sustainability imperatives. Engineering microbial systems through regulatory network rewiring and synthetic biology-driven functional augmentation substantially amplifies their biotechnological utility. Herein, we review the convergence of synthetic biology, bio-electrocatalysis, and reactor engineering as an integrated framework for sustainable biohydrogen production. Comparative analysis with conventional hydrogen generation strategies underscores the superiority of bioelectrochemical systems (BESs), which simultaneously enable wastewater valorisation and clean hydrogen production through microbially driven electron transfer cascades. Moreover, the mechanistic electron generation-to-hydrogen conversion continuum highlights the indispensable dominance of biotic catalysis. Furthermore, CRISPR-Cas9-mediated multiplex genome editing is examined as a precision tool surpassing traditional mutagenesis approaches for pathway optimisation. Key electrogenic taxa, their electrochemical interfaces and influences within BESs architectures, prevailing technological bottlenecks in scalability, techno-economic feasibilitites and forward-looking strategies toward wholly biological, scalable hydrogen production systems are critically featured.