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The genetic background and activities of the enzymes involved in H-2 production were investigated from ten distinct H-2 producing cyanobacteria, revealed by a recent screening. All strains are N-2- ...

Screening of the University of Helsinki Culture Collection for naturally good H2 producing cyanobacteria recently revealed several promising strains. One of the superior strains is Calothrix 336/3, an N2-fixing heterocystous filamentous cyanobacterium. Making use of an important feature of the Calothrix 336/3 cells to adhere to the substrate, we applied an immobilization technique to improve H2 production capacity of this strain. We examined the basic properties of immobilization in Ca2+-alginate films in response to the production of H2 of the Calothrix 336/3 strain and as reference strains we used a model organism Anabaena PCC 7120 and its uptake hydrogenase mutant, ΔhupL, that allow us to compare the responses of different strains to alginate entrapment. Immobilization of the Calothrix 336/3 and ΔhupL mutant cells in Ca2+-alginate resulted in prolonged H2 production over several cycles. Immobilization of the Calothrix 336/3 cells was most successful and production of H2 could be measured even after 40 days after immobilization.

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 H 2 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 H 2 producers. Approximately 50% of these strains produced detectable amounts of H 2 . Ten strains produced similar or up to 4 times as much of H 2 as the hydrogenase mutants of Anabaena PCC 7120 and Nostoc punctiforme ATCC 29133 specifically engineered in different laboratories to produce higher amounts of H 2 . All ten H 2 producers are N 2 -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 H 2 production rates of the two good H 2 producers, Calothrix 336/3 and XPORK 5E strains. Notably, the culture conditions for optimal H 2 production varied between different cyanobacterial strains.