Effect of photon fluence rate, nitrogen limitation and nitrogen recovery on the !ei'el of phyeoerythrin in the unicellular alga. Rhoilo.uniu mariiuis fRhodophyeeael. -Physiol. Plant. 92: 521-527.Studies vvere canied out on the etfects of itTadiance and nitrogen sources on phycoerythrin accumulation in the unicellular Rhodophvcea. RhudoMtrus mayinus. The ability of this microalgal species for natural cell aggregation was used to separate easily the biomass from the culture medium, Afler the temsnal oi nitrogen from the growth mediutn. phycoerythrin content decreased with time, faster the higher the fluence rate. The results suggest that, in A", niarlnus, a large pan of the phycoerythrin content of N-sufficicn! cells is used for nitrogen storage. Restoration of nitrogen in the growth medium induced an increase of phycoerythrin contem. even when cells were maintained in darkness. Dilfeient inorganic and organic nitrogen sourees were shown to protnote also phycoerythrin recoverv in the dark.
International audienceHere we investigate the effect of environmental pH on biomass and hydrocarbon productivity in photoautotro-phic cultures of Botryococcus braunii SAG 30.81 (race A). Successive steady-states of continuous cultures were used to study the effects of pH controlled by carbon dioxide feeds in a closed photobioreactor. At a fixed dilution rate of 0.2 d −1 , hydrocarbon productivity was found to be pH-dependent in the range 5.5 to 8.0, with an optimum at pH 6.5. pH variations from pH 6.0 to pH 8.0 had little effect on biomass productivity, nutrient requirement for biomass production, photosynthetic yield and pigment ratios, whereas acidic pH 5.5 conditions induced a slight decrease in biomass and hydrocarbon productivities as well as stressing the cells. The pH effect occurred even after a threefold increase in nitrate and phosphate concentrations in the feed culture medium, resulting in bio-mass productivity up to 8.9 g m −2 d −1 and hydrocarbon productivity up to 0.5 g m −2 d −1. Dissolved inorganic carbon data suggest that a maximum hydrocarbon content of 5.7% dry weight was reached at and above 1 mmol L −1 dissolved CO 2 and that hydrocarbon production was linearly related to CO 2 up to 2.5 mmol L −1 , whatever the N and P enrichment of AF-6 culture medium
Outline 4.1 Introduction (Jack Legrand) 4.2 Methods for biomass global characterization (Catherine Dupré) 4.3 Methods for protein determination in microalgae (Marilyne Fauchon, Claire Hellio) 4.4 Methods for polysaccharides determination in microalgae (Guillaume Pierre, Clément Gaignard, Cédric Delattre, Céline Laroche, Philippe Michaud) 4.5 Methods for lipids determination in microalgae (Junko Ito, Makoto M. Watanabe) 4.6 Methods for pigments determination in microalgae (Benoît Serive) 4.7 Methods for secondary metabolites determination in microalgae (Telma Encarnação, Alberto A.C.C. Pais, Maria G. Campos, Hugh D. Burrows) 4.8 ReferencesSome of them have to be considered for characterizing biomass from some biomineralized microalgae, such as diatoms or calcareous species [38]. The large biodiversity and chemodiversity of microalgae is of great interest in tapping in never exploited natural molecules, thanks to recent and ongoing screening studies. However, such diversity implies that the standard analytical protocols for biomass characterization have to be critically examined for potential interference.
Over the last decades, production of microalgae and cyanobacteria has been developed for several applications, including novel foods, cosmetic ingredients and more recently biofuel. The sustainability of these promising developments can be hindered by some constraints, such as water and nutrient footprints. This review surveys data on N2-fixing cyanobacteria for biomass production and ways to induce and improve the excretion of ammonium within cultures under aerobic conditions. The nitrogenase complex is oxygen sensitive. Nevertheless, nitrogen fixation occurs under oxic conditions due to cyanobacteria-specific characteristics. For instance, in some cyanobacteria, the vegetative cell differentiation in heterocyts provides a well-adapted anaerobic microenvironment for nitrogenase protection. Therefore, cell cultures of oxygenic cyanobacteria have been grown in laboratory and pilot photobioreactors (Dasgupta et al., 2010; Fontes et al., 1987; Moreno et al., 2003; Nayak & Das, 2013). Biomass production under diazotrophic conditions has been shown to be controlled by environmental factors such as light intensity, temperature, aeration rate, and inorganic carbon concentration, also, more specifically, by the concentration of dissolved oxygen in the culture medium. Currently, there is little information regarding the production of extracellular ammonium by heterocytous cyanobacteria. This review compares the available data on maximum ammonium concentrations and analyses the specific rate production in cultures grown as free or immobilized filamentous cyanobacteria. Extracellular production of ammonium could be coupled, as suggested by recent research on non-diazotrophic cyanobacteria, to that of other high value metabolites. There is little information available regarding the possibility for using diazotrophic cyanobacteria as cellular factories may be in regard of the constraints due to nitrogen fixation.
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