Effect of prolonged hypoxia in autotrophic conditions in the hydrogen production by the green microalga Chlamydomonas reinhardtii in photobioreactor

Abstract

In the context of hydrogen production by the green alga Chlamydomonas reinhardtii, the control of light attenuation conditions is used to set-up anoxia under illuminated and autotrophic conditions, without affecting photosynthetic capacities of cells (as with sulphur deprivation or PSII inhibitors like DCMU). This paper presents a full description of the protocol where the incident photons flux density (PFD) is adapted during cultivation in order to obtain a sufficiently low illuminated fraction γ under 0.25 leading to anoxic hydrogen producing conditions during several days. The protocol is validated in a torus-shape photobioreactor (PBR) revealing after few days of anoxic conditions a peak of hydrogen production (1.44 ml H2/h/l of culture; [0.8-1.0] ml H2/h/g of dry weight biomass) concomitant with a decrease of biomass concentration, protein content and maximal photosynthetic yield. Effect of over-accumulating starch, as being known to increase hydrogen production by the PSII-independent pathway, is also investigated.

Lumostatic strategy for microalgae cultivation utilizing image analysis and chlorophyll a content as design parameters

“…Microalgae have gained considerable attention and have been studied over the last decade by virtue of their high productivity, carbon sequestration potential and oil yield (Córdoba-Matson et al, 2010;Degrenne et al, 2011;Jena et al, 2011;Kliphuis et al, 2010). Microalgae are found to have higher photosynthetic efficiencies than most photoautotrophic organisms and have 10-50 times higher carbon removal efficiencies than other terrestrial plants (Li et al, 2008).…”

H2 production pathways in nutrient-replete mixotrophic Chlamydomonas cultures under low light. Response to the commentary article “On the pathways feeding the H2 production process in nutrient-replete, hypoxic conditions,” by Alberto Scoma and Szilvia Z. Tóth

“…In any case, the starch reserves do not seem to be linked to H 2 production [2, 3, 14]. Catabolism of proteins [2, 14] or acetate assimilation/dissimilation [3, 4, 10] are potential processes that can provide reductive power for PSII-independent H 2 production. However, conclusive results to characterizing the main electron source used for PSII-independent H 2 production under this condition are still missing.…”

Relevance of nutrient media composition for hydrogen production in Chlamydomonas

“…From studies in Chlamydomonas under autotrophic conditions, it is concluded that H 2 production is lower relative to mixotrophic conditions (Fouchard et al 2005;Tsygankov et al 2006;Kosourov et al 2007;Tolstygina et al 2009;Degrenne et al 2011), which reveal the importance of the presence of acetate in the medium composition.…”

“…This fact likely reflects the high NADH and electron demand of nitrate reductase and nitrite reductase, respectively, which contributes to the re-oxidation of the PEC and competes with HYDA for electrons. Improvement of the sustainability and efficiency of H 2 production under S deficiency using medium with different initial low S concentrations in mixotrophic (Fouchard et al 2009) and autotrophic (Degrenne et al 2011) cultures have been already performed. Similarly, continuous flow and readdition to the media of low S concentrations have been already assayed to optimize H 2 production Laurinavichene et al 2008;Tamburic et al 2013).…”