Extended H_2 photoproduction by N_2-fixing cyanobacteria immobilized in thin alginate films

摘要

Screening of the University of Helsinki Culture Collection for naturally good H_2 producing cyanobacteria recently revealed several promising strains. One of the superior strains is Calothrix 336/3, an N_2-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 H_2 production capacity of this strain. We examined the basic properties of immobilization in Ca~(2+)-alginate films in response to the production of H_2 of the Calothrix 336/3 strain and as reference strains we used a model organism Anabaena PCC 7120 and its uptake hydrogenase mutant, △hupL, that allow us to compare the responses of different strains to alginate entrapment. Immobilization of the Calothrix 336/3 and AhupL mutant cells in Ca~(2+)-alginate resulted in prolonged H_2 production over several cycles. Immobilization of the Calothrix 336/3 cells was most successful and production of H_2 could be measured even after 40 days after immobilization.