New aspects of the interplay of proton, electron and metabolite supply for photosynthetic H2 production in C. reinhardtii

A. Doebbe, J. Beckmann, and O. Kruse

Department of Biology/AlgaeBioTech Group, University of Bielefeld, 33615 Bielefeld, Germany

Phototrophic organisms use photosynthesis to convert solar energy into chemical energy. A select group of green algae and cyanobacteria have evolved the ability to use solar energy to extract protons (H+) and electrons (e ) from water (H2O) and to recombine these via the hydrogenase (H2ase) enzymes, to produce H2 from H2O. The substrates for the hydrogenase enzymes, H+ and e- can be supplied either directly from the water splitting reaction of photosystem II (PS II) or, in a more indirect way, from stored carbohydrates (starch) to fuel H2 production. We introduced the HUP1 (hexose uptake protein) hexose symporter from Chlorella kessleri into the high H2 production mutant Stm6. The isolated strain Stm6Glc4 can use externally supplied glucose for heterotrophic growth in the dark and in the light. More importantly, external glucose supply (1 mM) was shown to increase the H2 production capacity in strain Stm6Glc4 to ~150% of that of the high-H2 producing strain Stm6. This mutant offers the opportunity to analyse metabolic fluxes by external feeding of isotope labelled glucose.

e-mail address of presenting author: anja.doebbe@uni-bielefeld.de