[Show abstract][Hide abstract] ABSTRACT: 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 H2 production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus. The specific H2 production rates and yields were determined in the batch fermentation process. The best substrate was wheat straw, with H2 production capacity of 44.7 L H2 (kg dry biomass)−1 and H2 yield of 3.8 mol H2 (mol glucose)−1. Enzymatically pretreated maize leaves exhibited H2 production of 38 L H2 (kg dry biomass)−1. Slightly less H2 was obtained from homogenized whole plants of sweet sorghum. Sweet sorghum juice was an excellent H2 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 H2 production. The data were critically compared with recently published observations.
Full-text · Article · May 2009 · International Journal of Hydrogen Energy
[Show abstract][Hide abstract] ABSTRACT: The biopolymers agarose and alginic acid, and hemicellulose-rich pine tree wood shavings, frequently discarded as waste, proved to be utilized as energy sources for hydrogen production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus. The addition of 0.5% (w/v) pine wood shavings to the growth medium yielded a 14-fold increase in hydrogen production over a period of 55 days relative to cultures grown in the same medium without wood shavings (average rate was about 0.45 ml H2 ml culture−1 day−1). The shavings were also shown to be degraded by C. saccharolyticus in the absence of any other carbohydrate source.
A study on storage of the cells at 42 °C in the presence of either agarose or alginic acid cultures immobilized on granulated activated carbon, wood shavings or perlite revealed that the immobilization improved both the storability and hydrogen evolving capacity of the cells. From these carriers the soft wood shavings showed the best performance. The relevance of these findings for biohydrogen production is discussed.
Full-text · Article · Jan 2008 · International Journal of Hydrogen Energy
[Show abstract][Hide abstract] ABSTRACT: A brief overview is given of recent results on theory revision with queries for propo-sitional formulas, such as monotone and unate DNF, Horn formulas, read-once formulas, and threshold functions. Several open problems are formulated for revision in propositional and predi-cate logic, and finite automata.