Journal
APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY
Volume 162, Issue 1, Pages 208-220Publisher
HUMANA PRESS INC
DOI: 10.1007/s12010-009-8741-6
Keywords
Indirect biophotolysis; Cyanobacteria; Glycogen; DCMU
Funding
- Department of Energy National Energy Technology Laboratory
- Department of Energy Office of Science
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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 A mu mol/mg day) was observed in cultures with an initial medium nitrate concentration of 1 mM at a light intensity of 100 A mu mol/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.
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