Recent advances in reuse of waste material as substrate to produce biohydrogen by purple non-sulfur (PNS) bacteria

Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and non-polluting nature. Biological hydrogen production processes, mostly mediated photosynthetic bacteria, are more favorable candidates for biological hydrogen production due to their high conversion efficiency and versatility in the substrates (including wastewater) they can utilize. The potential utilization of waste material is being investigated extensively with suitable bioprocess technologies for providing cheaper raw materials with simultaneous waste treatment and bioremediation. Thus, this review article summarizes the biohydrogen production metabolism of purple non-sulfur (PNS) bacteria and research works involving biohydrogen production using various wastes such as tofu wastewater, palm oil mill effluent, olive mill wastewater, brewery wastewater, etc. by photosynthetic PNS bacteria. Waste materials used, yields and rates are reviewed, together with a discussion of the economics and perspectives of biohydrogen production from waste materials.