Dark and photofermentation H 2 production from hydrolyzed biomass of the potent extracellular polysaccharides producing cyanobacterium Nostoc commune and intracellular polysaccharide (glycogen) enriched Anabaena variabilis NIES-2095 Fatthy Mohamed Morsy a,b,* , Medhat Elbadry a,c , Wael S. El-Sayed a,d , Deia Abd El-Hady e,f a Biology Department, Faculty of Science, Taibah University, Medina, Saudi Arabia b Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut, Egypt c Microbiology Department, Faculty of Agriculture, Fayoum University, Cairo, Egypt d Microbiology Department, Faculty of Science, Ain Shams University, Cairo, Egypt e Chemistry Department, Faculty of Science, University of Jeddah, Jeddah, Saudi Arabia f Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt article info Article history: Received 22 March 2019 Received in revised form 25 April 2019 Accepted 4 May 2019 Available online xxx Keywords: Anabaena variabilis Biohydrogen Clostridium Cyanobacterial polysaccharides Nostoc commune Rhodobacter capsulatus abstract The biological H 2 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 Nostoc commune and glycogen (as intracellular polysaccharide) enriched Anabaena variabilis NIES-2095 were used as a cheap organic carbon feedstock for biological H 2 production by two stages dark fermentation by Escherichia coli strain MWW and Clos- tridium acetobutylicum DSM-792 or Clostridium beijerinckii DSM-1820 and photofermentation by Rhodobacter capsulatus 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 Escherichia coli strain MWW was used for maintaining anaerobiosis. Escherichia coli strain MWW was isolated and identified by morphological and biochemical characterizations as well as molecular biological phylogenetic analysis of its 16S rDNA sequence. Nostoc commune was identified by morphological and microscopic characteriza- tions and by 16S rDNA sequence phylogenetic analysis. The two stages dark fermentation by Escherichia coli and Clostridium acetobutylicum or Clostridium beijerinckii and photo- fermentation by Rhodobacter capsulatus produced in total 5.9 and 5.6 mol H 2 /mole reducing sugars of acid hydrolyzed Nostoc commune EPSs/biomass, respectively and 5.43 and 5 mol H 2 /mole reducing sugars of acid hydrolyzed biomass of glycogen enriched Anabaena vari- abilis, respectively. These results indicate a high potency of using cyanobacterial poly- saccharides/biomass (extracellular polysaccharides and intracellular glycogen) as an * Corresponding author. Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut, 71516, Egypt. E-mail address: fmorsy@aun.edu.eg (F.M. Morsy). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (xxxx) xxx https://doi.org/10.1016/j.ijhydene.2019.05.024 0360-3199/© 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article as: Morsy FM et al., Dark and photofermentation H 2 production from hydrolyzed biomass of the potent extra- cellular polysaccharides producing cyanobacterium Nostoc commune and intracellular polysaccharide (glycogen) enriched Anabaena variabilis NIES-2095, International Journal of Hydrogen Energy, https://doi.org/10.1016/j.ijhydene.2019.05.024