ABSTRACT
Hydrogen gas is considered to be one of the most desired alternate sources of the limited fossil energy resources of today. It shows great promise as a non-polluting fuel, but to reduce carbon dioxide releases hydrogen gas will need to be produced from renewable sources. The limited fossil fuel prompts the prospecting of various unconventional energy sources to take over the traditional fossil fuel energy source. Photosynthetic microbes can produce hydrogen using the nature plentiful resources, sunlight, the included greens, and blue-green algae [Cyanobacteria], either via direct or indirect biophotolysis. In addition, Cyanobacteria produced hydrogen through decomposing the organic compounds [Photodecomposition]. The hydrogen production by green algae could be considered as an economical and sustainable method, water utilization as a renewable resource and recycling CO[2], a greenhouse gas. Rates of hydrogen production by photoheterotrophic bacteria are higher in the case of immobilized cells than that of the suspended cells. Cyanobacteria are highly promising microorganism for hydrogen production. Cyanobacterial hydrogen production is commercially viable, in comparison to the traditional ways of hydrogen production [chemical, photoelectrical]. The present review shows the basic biology of microalgae and bacterial hydrogen production and its future prospects. While integrating the existing knowledge and technology, much future improvement and progress is to be done before hydrogen is accepted as a commercial primary energy source