Thermophilic biohydrogen production from energy plants by Caldicellulosiruptor saccharolyticus and comparison with related studies

Air-dried samples of sweet sorghum, sugarcane bagasse, wheat straw, maize leaves and silphium were utilized without chemical pretreatment as sole energy and carbon sources for H-2 production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus. The specific H-2 production rates and yields were determined in the batch fermentation process. The best substrate was wheat straw, with H-2 production capacity of 44.7 L H-2 (kg dry biomass)(-1) and H-2 yield of 3.8 mol H-2 (mol glucose)(-1). Enzymatically pretreated maize leaves exhibited H-2 production of 38 L H-2 (kg dry biomass)(-1). Slightly less H-2 was obtained from homogenized whole plants of sweet sorghum. Sweet sorghum juice was an excellent H-2 source. Silphium trifoliatum was also fermented though with a moderate production. The results showed that drying is a good storage method and raw plant biomass can be utilized efficiently for thermophilic H-2 production. The data were critically compared with recently published observations. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.