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The filamentous cyanobacterium Arthrospira platensis is an attractive feedstock for carbohydrate-based biofuels because it accumulated up to 74% of carbohydrates when nitrogen stressed. Nitrogen stressed A. platensis also settled spontaneously, and this occurred simultaneously with carbohydrates accumulation, suggesting a link between both phenomena. The increased settling velocity was neither due to production of extracellular carbohydrates, nor due to degradation of gas vacuoles, but was caused by an increase in the specific density of the filaments as a result of accumulation of carbohydrates under the form of glycogen. Settling velocities of carbohydrate-rich A. platensis reached 0.64mh(-1), which allowed the biomass to be harvested using a lamella separator. The biomass could be concentrated at least 15 times, allowing removal of 94% of the water using gravity settling, thus offering a potential application as a low-cost and high-throughput method for primary dewatering of carbohydrate-rich A. platensis. publisher: Elsevier articletitle: Harvesting carbohydrate-rich Arthrospira platensis by spontaneous settling journaltitle: Bioresource Technology articlelink: http://dx.doi.org/10.1016/j.biortech.2014.12.084 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved. ispartof: Bioresource Technology vol:180 pages:16-21 ispartof: location:England status: published

In this study the combined effect of total ammoniacal nitrogen (TAN) concentration, initial biomass density and initial pH of the cultivation medium on growth of A. platensis was studied. The results indicate that TAN inhibition in relation to the initial biomass in unregulated pH cultures is neither a clearly biomass-independent nor biomass-dependent phenomenon. However, low biomass densities are more susceptible to ammonia inhibition than higher biomass densities. Higher biomass densities seems to mitigate ammonia inhibition through rapider assmimilation of TAN. In all cases studied the growth rates were lower compared to the cultures with nitrate as nitrogen source. It was observed that at low TAN concentration, although no ammonia inhibition occured the growth rates were decreased due to nitrogen limitation. Low TAN concentration triggered the accumulation of carbohydrates affecting thus significantly the biomass composition. Ammonia losses from the cultivation system were also determined. Ammonia losses ranged between 17% and 80%. publisher: Elsevier articletitle: Ammonia inhibition on Arthrospira platensis in relation to the initial biomass density and pH journaltitle: Bioresource Technology articlelink: http://dx.doi.org/10.1016/j.biortech.2014.05.040 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved. ispartof: Bioresource Technology vol:166 pages:259-265 ispartof: location:England status: published