title: Ammonium photo-production by heterocytous cyanobacteria: potentials and constraints.
abstract: 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.
authors.affiliation: a LUNAM, Université de Nantes, CNRS, GEPEA , 44602 Saint-Nazaire Cedex , France and.
authors.forename: Dominique
authors.initials: D
authors.lastname: Grizeau
authors.affiliation: a LUNAM, Université de Nantes, CNRS, GEPEA , 44602 Saint-Nazaire Cedex , France and.
authors.forename: Lan Anh
authors.initials: LA
authors.lastname: Bui
authors.affiliation: a LUNAM, Université de Nantes, CNRS, GEPEA , 44602 Saint-Nazaire Cedex , France and.|b Conservatoire National des Arts et Métiers, Ecole SITI, EP Sciences et Techniques de la Mer, CNRS, GEPEA , 50103 Cherbourg Cedex , France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Dupré
authors.affiliation: a LUNAM, Université de Nantes, CNRS, GEPEA , 44602 Saint-Nazaire Cedex , France and.
authors.forename: Jack
authors.initials: J
authors.lastname: Legrand
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D018533:Biomass; D018914:Cells, Immobilized; D000458:Cyanobacteria / Q000378:metabolism*; D008027:Light
chemical_list: D064751:Ammonium Compounds
keywords: Ammonium excretion; N2 fixation; biomass production; cell immobilization; heterocytous cyanobacteria; photoautotrophy; photobioreactor