Title |
Improved Photobiological H2 Production in Engineered Green Algal Cells*
|
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Published in |
Journal of Biological Chemistry, August 2005
|
DOI | 10.1074/jbc.m503840200 |
Pubmed ID | |
Authors |
Olaf Kruse, Jens Rupprecht, Klaus-Peter Bader, Skye Thomas-Hall, Peer Martin Schenk, Giovanni Finazzi, Ben Hankamer |
Abstract |
Oxygenic photosynthetic organisms use solar energy to split water (H2O) into protons (H+), electrons (e-), and oxygen. A select group of photosynthetic microorganisms, including the green alga Chlamydomonas reinhardtii, has evolved the additional ability to redirect the derived H+ and e- to drive hydrogen (H2) production via the chloroplast hydrogenases HydA1 and A2 (H2 ase). This process occurs under anaerobic conditions and provides a biological basis for solar-driven H2 production. However, its relatively poor yield is a major limitation for the economic viability of this process. To improve H2 production in Chlamydomonas, we have developed a new approach to increase H+ and e- supply to the hydrogenases. In a first step, mutants blocked in the state 1 transition were selected. These mutants are inhibited in cyclic e- transfer around photosystem I, eliminating possible competition for e- with H2ase. Selected strains were further screened for increased H2 production rates, leading to the isolation of Stm6. This strain has a modified respiratory metabolism, providing it with two additional important properties as follows: large starch reserves (i.e. enhanced substrate availability), and a low dissolved O2 concentration (40% of the wild type (WT)), resulting in reduced inhibition of H2ase activation. The H2 production rates of Stm6 were 5-13 times that of the control WT strain over a range of conditions (light intensity, culture time, +/- uncoupler). Typically, approximately 540 ml of H2 liter(-1) culture (up to 98% pure) were produced over a 10-14-day period at a maximal rate of 4 ml h(-1) (efficiency = approximately 5 times the WT). Stm6 therefore represents an important step toward the development of future solar-powered H2 production systems. |
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Country | Count | As % |
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United Kingdom | 2 | <1% |
Germany | 1 | <1% |
Indonesia | 1 | <1% |
Italy | 1 | <1% |
Netherlands | 1 | <1% |
Portugal | 1 | <1% |
India | 1 | <1% |
South Africa | 1 | <1% |
Other | 5 | 2% |
Unknown | 216 | 93% |
Demographic breakdown
Readers by professional status | Count | As % |
---|---|---|
Student > Ph. D. Student | 57 | 24% |
Researcher | 40 | 17% |
Student > Master | 31 | 13% |
Student > Bachelor | 24 | 10% |
Professor | 12 | 5% |
Other | 32 | 14% |
Unknown | 37 | 16% |
Readers by discipline | Count | As % |
---|---|---|
Agricultural and Biological Sciences | 84 | 36% |
Biochemistry, Genetics and Molecular Biology | 30 | 13% |
Chemistry | 27 | 12% |
Engineering | 17 | 7% |
Environmental Science | 10 | 4% |
Other | 27 | 12% |
Unknown | 38 | 16% |