Screening for biohydrogen production by cyanobacteria isolated from the Baltic Sea and Finnish lakes

Cyanobacteria are the only bacteria capable of performing oxygenic photosynthesis in which they harness solar energy and convert it into chemical energy stored in carbohydrates. Under specific conditions, cyanobacteria can use solar energy to produce also molecular hydrogen.Biodiversity among cyanobacteria for H2 production has not been efficiently studied. Here we report the screening of 400 cyanobacterial strains isolated from the Baltic Sea and Finnish lakes for efficient H2 producers. Approximately 50% of these strains produced detectable amounts of H2. Ten strains produced similar or up to 4 times as much of H2 as the hydrogenase mutants of Anabaena PCC 7120 and Nostoc punctiforme ATCC 29133 specifically engineered in different laboratories to produce higher amounts of H2. All ten H2 producers are N2-fixing filamentous, heterocystous strains, seven of them are benthic and three are planktonic strains. Different culturing parameters, such as light intensity, cell density, pH and temperature had a pronounced effect on the H2 production rates of the two good H2 producers, Calothrix 336/3 and XPORK 5E strains. Notably, the culture conditions for optimal H2 production varied between different cyanobacterial strains.