title: Outdoor H₂ production in a 50-L tubular photobioreactor by means of a sulfur-deprived culture of the microalga Chlamydomonas reinhardtii.
abstract: In the past decade, H₂ production using the green microalga Chlamydomonas reinhardtii has been extensively studied under laboratory-scale photobioreactors, while information on outdoor cultures is still lacking. In this paper, the results of experiments conducted with sulfur-deprived cultures of C. reinhardtii carried out in a 50-L horizontal tubular photobioreactor are presented. Hydrogen production experiments were carried out under both artificial and direct solar light. In both cases, the H₂ output attained was 18-20% of what obtained in the laboratory. However, no significant changes in the H₂ production were observed when cells grown outdoors were tested under laboratory conditions. Chlorophyll fluorescence measurements showed that outdoor cultures were subjected to strong photo-inhibition, due to the combination of high solar light intensity and sulfur-deprivation. Indeed, H₂ production was only achieved outdoors when cultures were previously acclimated to sunlight, a condition that caused a number of physiological changes, namely: (i) a decrease in the chlorophyll content per unit of dry weight; (ii) an increase in the photosynthesis and respiration rates, and (iii) a higher induction of the xanthophyll cycle pigments as compared to non-acclimated cultures. It was concluded that the reduced H₂ output achieved in the 50-L photobioreactor was due to the different illumination pattern to which the cultures were exposed (one-sided vs. two-sided illumination provided in the laboratory), as well as to the great difference in the mixing times (60 min vs. 15.5s achieved in the lab-scale photobioreactor). To the very best of our knowledge this is the first time that H₂ production with green algae has been achieved by means of solar light.
authors.affiliation: Istituto per lo Studio degli Ecosistemi del Consiglio Nazionale delle Ricerche (CNR-ISE), via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Scoma
authors.forename: Luca
authors.initials: L
authors.lastname: Giannelli
authors.forename: Cecilia
authors.initials: C
authors.lastname: Faraloni
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Torzillo
mesh_terms: D000064:Acclimatization; D001709:Biotechnology / Q000295:instrumentation* / Q000379:methods*; D002241:Carbohydrates / Q000032:analysis; D016825:Chlamydomonas reinhardtii / Q000254:growth & development / Q000378:metabolism*; D005453:Fluorescence; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007558:Italy; D014975:Lutein / Q000378:metabolism; D058086:Microalgae / Q000254:growth & development / Q000378:metabolism*; D058433:Photobioreactors / Q000382:microbiology*; D010788:Photosynthesis; D010940:Plant Proteins / Q000032:analysis; D012621:Seasons; D013455:Sulfur / Q000172:deficiency*; D024341:Xanthophylls / Q000378:metabolism
chemical_list: D002241:Carbohydrates; D010940:Plant Proteins; D024341:Xanthophylls; D013455:Sulfur; D006859:Hydrogen; D014975:Lutein