STABLY SUSTAINED HYDROGEN-PRODUCTION BY BIOPHOTOLYSIS IN NATURAL DAY NIGHT CYCLE/

Our photobiological hydrogen production system was successfully scaled up to a pilot plant scale in the photosynthetic starch accumulation a nd the fermentative production of organic compounds from starch by Chl amydomonas MGA 161 and the hydrogen photoproduction by Rhodovulum sulf idophilum W-1S from organic compounds produced by Chlamydomonas MGA 16 1 in the natural day/night cycle, The conversion yield of organic comp ounds from starch of Chlamydomonas MGA 161 was 80 to 100 % of the theo retical yield, but the molar yield of hydrogen photoproduction of Rv. sulfidophilum W-1S was approximately 40 %. One main cause for the low hydrogen yield of Rv. sulfidophilum W-1S was a competition between the accumulation of intracellular Poly (3-hydroxybutyric acid), PHB, and the hydrogen production under light anaerobic conditions. The PHB accu mulation was repressed and the hydrogen photoproduction was promoted b y enhancing the nitrogenase activity of Rv. sulfidophilum W-1S. (C) 19 97 Elsevier Science Ltd.