초록
<P><B>Abstract</B></P><P>Screening of the University of Helsinki Culture Collection for naturally good H<SUB>2</SUB> producing cyanobacteria recently revealed several promising strains. One of the superior strains is <I>Calothrix</I> 336/3, an N<SUB>2</SUB>-fixing heterocystous filamentous cyanobacterium. Making use of an important feature of the <I>Calothrix</I> 336/3 cells to adhere to the substrate, we applied an immobilization technique to improve H<SUB>2</SUB> production capacity of this strain. We examined the basic properties of immobilization in Ca<SUP>2+</SUP>-alginate films in response to the production of H<SUB>2</SUB> of the <I>Calothrix</I> 336/3 strain and as reference strains we used a model organism <I>Anabaena</I> PCC 7120 and its uptake hydrogenase mutant, Δ<I>hupL</I>, that allow us to compare the responses of different strains to alginate entrapment. Immobilization of the <I>Calothrix</I> 336/3 and Δ<I>hupL</I> mutant cells in Ca<SUP>2+</SUP>-alginate resulted in prolonged H<SUB>2</SUB> production over several cycles. Immobilization of the <I>Calothrix</I> 336/3 cells was most successful and production of H<SUB>2</SUB> could be measured even after 40 days after immobilization.</P> <P><B>Highlights</B></P><P>► The <I>Calothrix</I> 336/3 cells entrapped in Ca<SUP>2+</SUP>-alginate films produce substantially more H<SUB>2</SUB> at much longer time course. ► Immobilization in Ca<SUP>2+</SUP>-alginate films stabilizes the filamentous cells, has a positive effect on cell viability, and reduces the growth of cells. ► CO<SUB>2</SUB> is an important determinant for efficient H<SUB>2</SUB> production in immobilized <I>Calothrix</I> 336/3 cultures.</P>