Biological hydrogen production from organic wastes is a less expensive, less energy-demanding, and environmental-friendly process. Pure monoculture delivers low H₂ content and low yield; these limitations are overcome by a defined co-culture system, which outperforms mixed cultures with increased H₂ yield. The strategies used in co-culture systems for increasing H₂ production have been discussed in this review. The strategies include hydrolysis of a variety of complex substrates, such as cellulose, molasses, crude glycerol, and algal biomass into simple fermentable sugars for increased H₂ yield by eliminating the use of exogenous enzymes. The strategies can bring geographically distant isolated microorganisms from different sources to coexist for simultaneous utilization of substrate and end metabolites into H₂ production of 99.99% purity without the expenses of reducing agents. In the case of maximum hydrogen production using co-culture strategies, Clostridium, Enterobacter, and photo-fermenting bacteria in a consolidated bioprocess system will result in increased H₂ yield. A co-culture system is more feasible to achieve theoretical H₂ yield with high conversion efficiency of organic wastes, enhance the economic viability of H₂ production, provide better effluent treatment quality, and concurrently address the limitations of H₂ production. Copyright © 2015 John Wiley & Sons, Ltd.

Enhanced biological hydrogen production from industrial wastes through a co-culture system with two or more pure cultures has several advantages over monoculture. With co-culture strategies, hydrolysis of complex substrate, process improvements, use of immobilization technique, end metabolite utilization, co-substrate supplementation, and combined dark and photo-fermentation resulted in increased hydrogen production. In case of maximum hydrogen production using co-culture strategies, Clostridium, Enterobacter, and photo-fermenting bacteria are the best choice of microorganism.