Monday, May 4, 2009
11-25
Hydrogen production from COSLIF-treated cellulosic feedstocks
Steve Harvey1, Amanda E.1, and Percival Zhang2. (1) Research & Technology Directorate, USA Army RDECOM, ECBC, E5183 Blackhawk Road, Aberdeen Proving Ground, MD 21010, (2) Biological Systems Engineering Department, Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech University, 210-A Seitz Hall, Blacksburg, VA 24061
Clostridium phytofermentans is a recently-discovered anaerobe, previously reported to hydrolyze cellulose and to ferment five and six carbon sugars and starch into ethanol. We developed a chemically-defined medium in which to grow C. phytofermentans and observed that after a very long lag time, C. phytofermentans would fix its own nitrogen from N2 gas. The native strain was inoculated into a 5 L chemostat in defined medium with N2 as the sole source of nitrogen for growth (conditions designed to select for mutants with increased nitrogenase activity). The culture was continuously mutated in a loop run past a UV light under conditions yielding about 90% killing. The growth rate increased dramatically over this time and a variant (cpnit-1), with a 33% increased growth rate under nitrogen fixing conditions. Experiments with cpnit-1 have produced two moles of H2 per mole of glucose under N2 fixation conditions. H2 production has been shown to be inversely proportional to ammonia concentration, consistent with enhanced or deregulated nitrogenase activity as the source of H2. Experiments with cellulosic feedstocks including Phragmites australis show greatly increased H2 production from Cellulose and Organic Solvent-based Lignocellulose Fractionation (COSLIF) treated feedstock as compared to untreated material.