초록
<P><B>Abstract</B></P> <P>H<SUB>2</SUB> produced by cyanobacteria is one of the interesting alternative energy carriers for the future. The filamentous N<SUB>2</SUB>-fixing cyanobacterium <I>Anabaena siamensis</I> TISTR 8012 is a potential microorganism for H<SUB>2</SUB> production. It can produce H<SUB>2</SUB> via both photosynthesis and nitrogen fixation processes. This study aimed to increase the efficiency of H<SUB>2</SUB> production by immobilization of <I>A. siamensis</I> cells. The result showed that H<SUB>2</SUB> production rate by <I>A. siamensis</I> grown in BG11<SUB>0</SUB> medium was higher than that in BG11 and Allen-Arnon media due to an increase of the heterocyst cells. The sulfur deprivation during adaptation period for 24 hours increased its H<SUB>2</SUB> production rate. The optimal conditions for H<SUB>2</SUB> production by immobilized cells were immobilization with alginate and using 150 gel beads in 20 mL glass vial. In immobilized cells, an addition of 0.5% fructose resulted in a 2-fold increase of H<SUB>2</SUB> production rate. Finally, the reducing agents β–mercaptoethanol and methylviologen enhanced H<SUB>2</SUB> production rate with 3.092 and 2.426 µmolH<SUB>2</SUB> mg chl a<SUP>-1</SUP> h<SUP>-1</SUP>, respectively, in <I>A. siamensis</I> immobilized cells whereas NADH, dithiothreitol and sodium dithionite were not capable of increasing H<SUB>2</SUB> production rate.</P>