The increase in global carbon footprints forced mankind to look for alternative carbon‐free fuels. Biohydrogen is an ideal fuel, free of carbon footprint, which has the potential to replace fossil fuels. Its high energy content per gram has a great commercial value. Bacteria, cyanobacteria, and algae are developed with various cellular machineries for hydrogen production. Detailed information on these hydrogen‐producing cellular machineries, their mechanism of catalysis, and modern genetic engineering and fabrication studies for the enhancement of hydrogen production are reviewed and discussed.

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