CONTROL OF PHOTOSYNTHETIC REDUCTANT: THE ROLE OF LIGHT AND TEMPERATURE ON SUSTAINED HYDROGEN PHOTOEVOLUTION BY Chlamydomonas sp. IN AN ANOXIC, CARBON DIOXIDE‐CONTAINING ATMOSPHERE*

Graves, Duane; Tevault, C. V.; Greenbaum, Elias

doi:10.1111/j.1751-1097.1989.tb05566.x

Cited by 16 publications

(7 citation statements)

References 21 publications

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“…In the absence of O 2 both ATP production by oxidative phosphorylation, and the formation of NADH/NADPH are inhibited [67]. Under these conditions, certain microalgae, such as C. reinhardtii reroute the energy stored in carbohydrates such as starch to the chloroplast hydrogenase [63,111] to facilitate ATP production via photophosphorylation and to keep the electron transport chain from over-reduction (see [96,151] for a review; Fig.…”

Section: Algal Biohydrogen Productionmentioning

confidence: 99%

Second Generation Biofuels: High-Efficiency Microalgae for Biodiesel Production

et al. 2008

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The use of fossil fuels is now widely accepted as unsustainable due to depleting resources and the accumulation of greenhouse gases in the environment that have already exceeded the "dangerously high" threshold of 450 ppm CO 2 -e. To achieve environmental and economic sustainability, fuel production processes are required that are not only renewable, but also capable of sequestering atmospheric CO 2 . Currently, nearly all renewable energy sources (e.g. hydroelectric, solar, wind, tidal, geothermal) target the electricity market, while fuels make up a much larger share of the global energy demand (∼66%). Biofuels are therefore rapidly being developed. Second generation microalgal systems have the advantage that they can produce a wide range of feedstocks for the production of biodiesel, bioethanol, biomethane and biohydrogen. Biodiesel is currently produced from oil synthesized by conventional fuel crops that harvest the sun's energy and store it as chemical energy. This presents a route for renewable and carbon-neutral fuel production. However, current supplies from oil crops and animal fats account for only approximately 0.3% of the current demand for transport fuels. Increasing biofuel production on arable land could have severe consequences for global food supply. In contrast, producing biodiesel from algae is widely regarded as one of the most efficient ways of generating biofuels and also appears to represent the only current renewable source of oil that could meet the global demand for transport fuels. The main advantages of second generation microalgal systems are that they: (1) Have a higher photon conversion efficiency (as evidenced by increased biomass yields per hectare): (2) Can be harvested batch-wise nearly all-year-round, providing a reliable and continuous supply of oil: (3) Can utilize salt and waste water streams, thereby greatly reducing freshwater use: (4) Can couple CO 2 -neutral fuel production with CO 2 sequestration: (5) Produce non-toxic and highly biodegradable biofuels. Current limitations exist mainly in the harvesting process and in the supply of CO 2 for high efficiency production. This review provides a brief overview of second generation biodiesel production systems using microalgae. AbbreviationsBTL biomass to liquid CFPP cold filter plugging point CO 2 -e-CO 2 equivalents of greenhouse gases NEB net energy balance LHC light harvesting complex OAE oceanic anoxic event PS photosystem

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Section: Algal Biohydrogen Productionmentioning

confidence: 99%

Second Generation Biofuels: High-Efficiency Microalgae for Biodiesel Production

et al. 2008

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“…When such algae are exposed to light, the water-splitting complex of Photosystem II (PS II) provides reducing equivalents for the photoproduction of molecular hydrogen (catalyzed by hydrogenase), instead of carbon fixation. Chlamydomonas reinhardtii is another algal species that possesses the ability to perform biophotolysis of water (Reeves and Greenbaum 1985, Graves et al 1988, Greenbaum 1988b, Graves et al 1989.…”

Section: Introductionmentioning

confidence: 99%

“…At the • same time, of course, CO 2 is the key reagent of the Calvin cycle as the terminal electron acceptor and activator of crucial enzymes (Lorimer et al 1976). Under anaerobiosis, the Calvin cycle competes with hydrogenase for electrons activated by Photosystems I and II (PS I and II) and overwhelms it when high amounts of CO 2 (1% in helium) are present (Graves et al 1989). By titrating the CO: concentration in an algal environment, a value was sought such that enough inorganic CO 2 would be present to maintain relatively high PET rates while restricting supply of the basic reagent of the Calvin cycle.…”

Section: Introductionmentioning

confidence: 99%

The role of carbon dioxide in light-activated hydrogen production by Chlamydomonas reinhardtii

1993

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Light-activated hydrogen and oxygen evolution as a function of CO2 concentration in helium were measured for the unicellular green alga Chlamydomonas reinhardtii. The concentrations were 58, 30, 0.8 and 0 ppm CO2. The objective of these experiments was to study the differential affinity of CO2/HCO 3 (-) for their respective Photosystem II and Calvin cycle binding sites vis-à-vis photoevolution of molecular oxygen and the competitive pathways of hydrogen photoevolution and CO2 photoassimilation. The maximum rate of hydrogen evolution occurred at 0.8 ppm CO2, whereas the maximum rate of oxygen evolution occurred at 58 ppm CO2. The key result of this work is that the rate of photosynthetic hydrogen evolution can be increased by, at least partially, satisfying the Photosystem II CO2/HCO 3 (-) binding site requirement without fully activating the Calvin-Benson CO2 reduction pathway. Data are presented which plot the rates of hydrogen and oxygen evolution as functions of atmospheric CO2 concentration in helium and light intensity. The stoichiometric ratio of hydrogen to oxygen changed from 0.1 at 58 ppm to approximately 2.5 at 0.8 ppm. A discussion of partitioning of photosynthetic reductant between the hydrogen/hydrogenase and Calvin-Benson cycle pathways is presented.

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“…Anaerobically maintained Chlamydomonas generates H 2 in the light or dark through photosynthetic and fermentative pathways, respectively. Transient H 2 photoproduction is observed after illumination of dark, anaerobically acclimated cells grown in nutrient-replete medium (4,21,23,24,26,42). However, H 2 production rates rapidly diminish as the O 2 , generated from photosynthesis increases to inhibitory levels.…”

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confidence: 97%

Anaerobic Acclimation in Chlamydomonas reinhardtii

Mus

Dubini

Seibert

et al. 2007

Journal of Biological Chemistry

279

156

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Both prokaryotic and eukaryotic photosynthetic microbes experience conditions of anoxia, especially during the night when photosynthetic activity ceases. In Chlamydomonas reinhardtii, dark anoxia is characterized by the activation of an extensive set of fermentation pathways that act in concert to provide cellular energy, while limiting the accumulation of potentially toxic fermentative products. Metabolite analyses, quantitative PCR, and high density Chlamydomonas DNA microarrays were used to monitor changes in metabolite accumulation and gene expression during acclimation of the cells to anoxia. Elevated levels of transcripts encoding proteins associated with the production of H 2 , organic acids, and ethanol were observed in congruence with the accumulation of fermentation products. The levels of over 500 transcripts increased significantly during acclimation of the cells to anoxic conditions. Among these were transcripts encoding transcription/translation regulators, prolyl hydroxylases, hybrid cluster proteins, proteases, transhydrogenase, catalase, and several putative proteins of unknown function. Overall, this study uses metabolite, genomic, and transcriptome data to provide genome-wide insights into the regulation of the complex metabolic networks utilized by Chlamydomonas under the anaerobic conditions associated with H 2 production.

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CONTROL OF PHOTOSYNTHETIC REDUCTANT: THE ROLE OF LIGHT AND TEMPERATURE ON SUSTAINED HYDROGEN PHOTOEVOLUTION BY Chlamydomonas sp. IN AN ANOXIC, CARBON DIOXIDE‐CONTAINING ATMOSPHERE*

Cited by 16 publications

References 21 publications

Second Generation Biofuels: High-Efficiency Microalgae for Biodiesel Production

Second Generation Biofuels: High-Efficiency Microalgae for Biodiesel Production

The role of carbon dioxide in light-activated hydrogen production by Chlamydomonas reinhardtii

Anaerobic Acclimation in Chlamydomonas reinhardtii

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