title: Hydrogen generation through indirect biophotolysis in batch cultures of the nonheterocystous nitrogen-fixing cyanobacterium Plectonema boryanum.
abstract: The nitrogen-fixing nonheterocystous cyanobacterium Plectonema boryanum was used as a model organism to study hydrogen generation by indirect biophotolysis in nitrogen-limited batch cultures that were continuously illuminated and sparged with argon/CO(2) to maintain anaerobiosis. The highest hydrogen-production rate (i.e., 0.18 mL/mg day or 7.3 micromol/mg day) was observed in cultures with an initial medium nitrate concentration of 1 mM at a light intensity of 100 micromol/m(2) s. The addition of photosystem II (PSII) inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) did not reduce hydrogen-production rates relative to unchallenged controls for 50 to 150 h, and intracellular glycogen concentrations decreased significantly during the hydrogen generation period. The insensitivity of the hydrogen-production process to DCMU is indicative of the fact that hydrogen was not derived from water splitting at PSII (i.e., direct biophotolysis) but rather from electrons provided by intracellular glycogen reserves (i.e., indirect biophotolysis). It was shown that hydrogen generation could be sustained for long time periods by subjecting the cultures to alternating cycles of aerobic, nitrogen-limited growth and anaerobic hydrogen production.
authors.affiliation: Marine Sciences Laboratory, Pacific Northwest National Laboratory, 1529 West Sequim Bay Road, Sequim, WA 98382, USA. michael.huesemann@pnl.gov
authors.forename: Michael H
authors.initials: MH
authors.lastname: Huesemann
authors.forename: Tom S
authors.initials: TS
authors.lastname: Hausmann
authors.forename: Blaine M
authors.initials: BM
authors.lastname: Carter
authors.forename: Jared J
authors.initials: JJ
authors.lastname: Gerschler
authors.forename: John R
authors.initials: JR
authors.lastname: Benemann
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D003470:Culture Media / Q000737:chemistry; D046508:Culture Techniques / Q000379:methods*; D004237:Diuron / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006859:Hydrogen / Q000378:metabolism*; D008027:Light; D009566:Nitrates / Q000494:pharmacology; D009586:Nitrogen Fixation; D010782:Photolysis; D046938:Plectonema / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D003470:Culture Media; D009566:Nitrates; D006859:Hydrogen; D004237:Diuron