Hydrogen Generation Through Indirect Biophotolysis in Batch Cultures of the Nonheterocystous Nitrogen-Fixing Cyanobacterium <Emphasis Type="Italic">Plectonema boryanum</Emphasis> |
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Authors: | Michael H Huesemann Tom S Hausmann Blaine M Carter Jared J Gerschler John R Benemann |
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Institution: | (1) Marine Sciences Laboratory, Pacific Northwest National Laboratory, 1529 West Sequim Bay Road, Sequim, WA 98382, USA;(2) Benemann Associates, 3434 Tice Creek Drive, #1, Walnut Creek, CA 94595, USA |
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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/CO2 to maintain anaerobiosis. The highest hydrogen-production rate (i.e., 0.18 mL/mg day or 7.3 μmol/mg day) was observed in
cultures with an initial medium nitrate concentration of 1 mM at a light intensity of 100 μmol/m2 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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