Optimization of Arthrospira platensis (Spirulina) Growth: From Laboratory Scale to Pilot Scale

Abstract

Arthrospira platensis (Spirulina) is the most cultivated microalga worldwide. Improving its cultivation in terms of biomass productivity, quality, or production cost could significantly impact the Spirulina industry. The objectives of this paper were defined as to contribute to this goal. Spirulina biomass productivity was investigated through medium choice. A modified Zarrouk's medium was selected as it gave higher final dry weights and longer sustained growth than Hiri's and Jourdan's media. Then, in order to reduce Spirulina production cost, modified Zarrouk's medium was rationalized by testing different dilutions. It was found that modified Zarrouk's medium could be diluted up to five times without impacting the growth rates in a 28-days batch cultivation. Higher dry weights were even observed after 21 days of batch cultivation (1.21 g/L for 20%-modified Zarrouk's medium in comparison to 0.84 g/L for modified Zarrouk's medium). Iron uptake was then investigated as one of the major contributors to Spirulina nutritional quality. An increase in iron content was obtained by replacing iron sulfate by iron EDTA at a concentration of 10 mg Fe /L (2.11 ± 0.13 mg Fe /g biomass for EDTA-FeNa,3H 2 O at 10 mg Fe /L compared to 0.18 ± 0.13 for FeSO 4 ,6H 2 O at 2 mg Fe /L). Impact of light intensity on Spirulina biomass productivity was also investigated in a 2 L Photobioreactor (PBR). Specific growth rates were calculated for Photosynthetically Photon Flux Densities (PPFD) from 85 to 430 µmol/m 2 /s. At 430 µmol/m 2 /s, photoinhibition was not observed and the specific growth rate was maximum (0.12/day). Finally, a 40-day cultivation experiment was conducted in a 1000 L PBR giving a maximum daily areal productivity of 58.4 g/m 2 /day. A techno-economic analysis gave production cost two to 20 times higher for PBR (from 18.71 to 74.29 €/kg) than for open ponds (from 3.86 to 9.59 €/kg) depending on Spirulina productivity.

Long-Term Cultivation of a Native Arthrospira platensis (Spirulina) Strain in Pozo Izquierdo (Gran Canaria, Spain): Technical Evidence for a Viable Production of Food-Grade Biomass

“…Culture volumetric productivity varied between 0.04 and 0.08 g/L/day (overall mean value: 0.06 ± 0.012 g/L/day; Table 1), with the highest productivities recorded at the days 0-6 for the F phase and at the days 42-46 for the R phase (0.08 ± 0.002 and 0.07 ± 000.2 g/L/day, respectively). A negative correlation between productivity rate and initial culture concentration at each semi-continuous cycle was found (r = −0.83; p < 0.05), in accordance with previous reports that underline a reciprocal shadowing effect occurring at high cell densities [8,52]. Average productivity did not differ significantly between the two phases (mean value: 0.06 ± 0.016 and 0.06 ± 0.010 g/L/day for F and R phase, respectively).…”

“…Daily evaporation of the A. platensis BEA 1257B culture during the course of the experiment (mean value: 3.9 ± 1.0 mm for F and 3.0 ± 1.1 mm for R phase; p < 0.01) was lower than that recorded in open ponds located in arid or semi-arid areas ( 6 mm), likely due to an increased relative humidity in the surrounding atmosphere enabled from the greenhouse barrier [8,26,34]. This water-loss limitation accounts for more than a one-third reduction in the water demand due to evaporation, this latter being estimated around the 35% of the total water demand for freshwater microalgae cultivation [56].…”

“…Mesophilic, alkaliphilic cyanobacteria of the genus Arthrospira, commonly known as Spirulina, are by far the most cultivated photosynthetic microorganisms globally, with a worldwide production exceeding 10,000 tons of dry biomass annually [7][8][9]. The edible species Arthrospira platensis has been certified as a "Generally Recognized as Safe" (GRAS) supplement by the United States Food and Drug Administration Agency (FDA).…”

Growth Enhancement of Spirulina platensis through Optimization of Media and Nitrogen Sources

“…Salunke et al (2016), regarded that urea is more effective than KNO 3 for S. platensis. The previous studies demonstrated that the availability and concentration of nitrogen source influence the microalgal proteins content (Markou, 2015;Li et al, 2016) Delrue et al (2017 reported that when Spirulina was cultivated for 40 days cultivation in a 1000L-photobioreactor during spring 2015. This period of cultivation helped to increase the possibility of Spirulina growth in the photobioreactor and improving biomass productivity.…”

Spirulina platensis Protein as Sustainable Ingredient for Nutritional Food Products Development

“…In some trace minerals (Mn, Zn, and Se), the amounts were lower compared to the three sources previously mentioned [47]. The variation in microalgae biomass composition often results from different culture conditions such as the stress parameters (temperature and light intensity, among others) used for its cultivation [48]. Some studies have compared several environmental factors (nitrogen concentrations, pH, CO 2 , etc.)…”