초록
<P><B>Abstract</B></P> <P>The biological H<SUB>2</SUB> production industry would be independent from other industries if it has its own supply of organic materials especially in non-agricultural countries. In this study, acid hydrolyzed biomass of the potent extracellular polysaccharides (EPSs) producing cyanobacterium <I>Nostoc commune</I> and glycogen (as intracellular polysaccharide) enriched <I>Anabaena variabilis</I> NIES-2095 were used as a cheap organic carbon feedstock for biological H<SUB>2</SUB> production by two stages dark fermentation by <I>Escherichia coli</I> strain MWW and <I>Clostridium acetobutylicum</I> DSM-792 or <I>Clostridium beijerinckii</I> DSM-1820 and photofermentation by <I>Rhodobacter capsulatus</I> JCM-21090 under anaerobic conditions. Acid hydrolysis of air dried cyanobacterial biomass was conducted at optimum conditions of 4 M HCl at 120 °C in an autoclave for 30 min and subsequently neutralized and used as an organic carbon source for first stage dark fermentation followed by a second stage photofermentation. The facultative anaerobe <I>Escherichia coli</I> strain MWW was used for maintaining anaerobiosis. <I>Escherichia coli</I> strain MWW was isolated and identified by morphological and biochemical characterizations as well as molecular biological phylogenetic analysis of its 16S rDNA sequence. <I>Nostoc commune</I> was identified by morphological and microscopic characterizations and by 16S rDNA sequence phylogenetic analysis. The two stages dark fermentation by <I>Escherichia coli</I> and <I>Clostridium acetobutylicum</I> or <I>Clostridium beijerinckii</I> and photofermentation by <I>Rhodobacter capsulatus</I> produced in total 5.9 and 5.6 mol H<SUB>2</SUB>/mole reducing sugars of acid hydrolyzed <I>Nostoc commune</I> EPSs/biomass, respectively and 5.43 and 5 mol H<SUB>2</SUB>/mole reducing sugars of acid hydrolyzed biomass of glycogen enriched <I>Anabaena variabilis</I>, respectively. These results indicate a high potency of using cyanobacterial polysaccharides/biomass (extracellular polysaccharides and intracellular glycogen) as an organic carbon source for H<SUB>2</SUB> production which would be of importance for non-agricultural countries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>N. commune</I> extracellular polysaccharides/biomass was efficient for H<SUB>2</SUB> production. </LI> <LI> Intracellular glycogen enriched <I>Anabaena</I> biomass was efficient for H<SUB>2</SUB> production. </LI> <LI> <I>E. coli</I> was used for maintaining anaerobiosis for H<SUB>2</SUB> production by <I>Clostridium</I>. </LI> <LI> H<SUB>2</SUB> production was efficiently conducted by two stages dark and photo-fermentation. </LI> <LI> Cyanobacterial polysaccharides would be useful for non-agricultural countries. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>