title: Use of natural pH variation to increase the flocculation of the marine microalgae Nannochloropsis oculata.
abstract: Microalgae is largely used in aquaculture as feed. More recently, these microorganisms have been considered as an important feedstock for biodiesel production. However, the concentration of produced biomass represents a large parcel of production costs. In this study, we have evaluated the influence of natural pH variation of culture medium, caused by photosynthetic activity, on the flocculation of the marine microalgae Nannochloropsis oculata. Experiments were conducted with the same culture with different pH values (8.5 and 9.6), obtained after exposing the cells to different light conditions. For each pH value, different treatments were composed by adding 0, 5, 10, and 30 mM of NaOH and the flocculant Flopam® (FO4800 SH) at concentrations of 0, 0.5, 1, and 5 ppm. Higher flocculation efficiencies were obtained for the culture with pH 9.6 in comparison to 8.5 for the same NaOH and Flopam concentrations. Lower concentrations of base and flocculant were needed for flocculating the culture in higher pH, representing an economy of 20 % in the costs of crop harvesting.
authors.affiliation: Institute of Oceanography, Federal University of Rio Grande-FURG, Av. Italia, Km 08, CEP 96201-900, Rio Grande, RS, Brazil, rafael_ojs@hotmail.com.
authors.forename: Rafael
authors.initials: R
authors.lastname: Sales
authors.forename: Paulo Cesar
authors.initials: PC
authors.lastname: Abreu
mesh_terms: D000180:Acrylic Resins / Q000494:pharmacology*; D056804:Biofuels; D018533:Biomass; D003470:Culture Media / Q000737:chemistry; D005427:Flocculation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008027:Light; D058086:Microalgae / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D010788:Photosynthesis / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D012972:Sodium Hydroxide / Q000494:pharmacology*; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D056804:Biofuels; D003470:Culture Media; D012972:Sodium Hydroxide; D000099166:Polyacrylamides