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The objective of this research was to study the effects of different feed formulas on the growth of Spirulina and water quality in terms of temperature, pH and light intensity. The experiment was designed with completely randomized design (CRD), divided into 3 sets of treatments with different feed formulas with 3 replicates, using formula 1(Zarrouk’s medium as control formula); formula 2(Zarrouk’s medium mixed with 100 ml/1,000 ml of rice straw ferment liquid), and formula 3(Zarrouk’s medium mixed with 200 ml/1,000 ml of rice straw ferment liquid) with 10 days cultured period provided with 24-hour light cycle. The growth efficiency was measured by measuring the average of Optical Density (OD), using a spectrophotometer at the wavelength of 560 nm. The results showed that the growth rate of Spirulina cultured with formula 1 was a statistically significantly different level of 95 % confidence (p<0.05) with, the growth rate of Spirulina cultured with formula 2 and 3. While the growth rate of Spirulina cultured with formulas 2 and 3 was not statistically different at a statistical significance level of 95 % confidence (p>0.05). In terms of water quality throughout the Spirulina culture, the temperature and pH values were in the range of 26.80±0.53 - 32.40±0.30 °C and 9.46±0.05 - 10.12±0.09, while the light intensity values were in the range of 1,125 - 1,950 lux, respectively [ABSTRACT FROM AUTHOR]

Fresh Spirulina is more favorable than dried one, yet its ease of deterioration necessitates production of biomass that can be immediately consumed. We developed a prototype household photobioreactor and studied the semi-continuous cultivation and harvest conditions within 107 days. Three growth phases were observed featuring different growth rate and recovering time after harvest. Nutrients were consumed at rates of Fe > N > P > Mg > K. The pH mounted rapidly when below 9 and varied slowly between 9 and 10, whose variation positively correlated with that of biomass concentration. Bacterial load was at a constant level of about 2 × 104 CFU, indicating good sanitary condition. Harvesting efficiency improved with greater biomass and filtration sack mesh number until reaching 3.5 g·L−1 and 200, respectively. We hope this study can help the method development of fresh Spirulina cultivation in miniaturized systems.

Special properties and various applications of Spirulina species have led to the growing focus of biotechnology to the cost effective cultivation. Open ponds used in the most commercial cultivation have many deficiencies such as risk of contamination, lack of light penetration, inefficient mixing and low productivity. In this study, an innovative reactor was designed and manufactured. By adding a control area, it was possible to control some environmental conditions for a limited amount of open pond volume. The conventional pumping system was replaced by a new elevator system to reduce the damage of to the fragile cells. The baffles structure and aeration from bottom, contributed to better mixing system. The effect of tree factors (Circulation Cycle (Cir. Cyc.), Control Volume (Con.Vol.) and Irradiance Intensity (Irr. Int.) in units of hours, percentage and Lux respectively) on the quantity of biomass (Specific Growth Rate (SGR, day-1) and fifth and seventh day dry weight (g/L)) were evaluated using RSM-CCD. The maximum biomass dry weight (0.915 g/L) was achieved in longest circulation cycle (12 hours), 30% Con. Vol. and 7000 Lux light intensity. The optimal irradiance intensity to achieve the highest biomass was 8700 Lux. According to the results, due to the great influence of Con. Vol. and Cir. Cyc., it is possible to increase the productivity and enhance the culture dry weight by controlling a limited amount of ponds volume (20%), subject to economic considerations. These successful results can provide the context using a control zone for several open ponds to improve the overall efficiency.

Biomass and photosynthetic pigments production of cyanobacteria, in particular Spirulina (Arthrospira platensis), depend on light intensity. Production cost of Spirulina cultivation in photobioreactor illuminated with LED is strongly related to light cost. This work is aimed to evaluate the effects of light intensity and photoperiod on the energy efficiency of biomass and pigment production of Spirulina platensis UTEX 1926. Cultures illuminated with white light-emitting diodes (LED) were carried out in batch mode cultivation. Three lighting scenarios with different light intensities were tested: two with a constant light intensity at 80 and 160 μmol · m−2 · s−1 and one with modulated light intensity. Concerning photoperiod, three cycles of light:dark (h:h) (24:00, 20:04 and 16:08) were studied under light intensity at 160 μmol · m−2 · s−1. Concerning Spirulina biomass and pigment production (phycocyanin, chlorophyll and carotenoids), it is found that the lower intensity tested allows a substantial increase of the process energy efficiency. Concerning the influence of the photoperiod, it has been found that the longer the off time is (up to 08 h 00 a day), the higher is the energy efficiency for Spirulina biomass as well as for pigmentary production. [ABSTRACT FROM AUTHOR]

Fresh Spirulina is more favorable than dried one, yet its ease of deterioration necessitates production of biomass that can be immediately consumed. We developed a prototype household photobioreactor and studied the semi-continuous cultivation and harvest conditions within 107 days. Three growth phases were observed featuring different growth rate and recovering time after harvest. Nutrients were consumed at rates of Fe > N > P > Mg > K. The pH mounted rapidly when below 9 and varied slowly between 9 and 10, whose variation positively correlated with that of biomass concentration. Bacterial load was at a constant level of about 2 × 104 CFU, indicating good sanitary condition. Harvesting efficiency improved with greater biomass and filtration sack mesh number until reaching 3.5 g·L−1 and 200, respectively. We hope this study can help the method development of fresh Spirulina cultivation in miniaturized systems. [ABSTRACT FROM AUTHOR]

Spirulina ( Arthrospira ) platensis is the most commonly produced microalgae for commercial applications, such as nutraceuticals and feed. While crop productivity of commercial Spirulina farms is often compromised by grazers and contaminating microzooplanktons, the biodiversity and identity of the most harmful microzooplanktons in Spirulina farms have not been extensively studied. As China is the number one producer of Spirulina in the world, comprehensive information on the biodiversity and identity of microzooplanktons in Spirulina farms is essential for the long-term commercial viability of these farms. Therefore, we determined the biodiversity and identity of the major microzooplanktons that are present in eight commercial Spirulina cultivation sites throughout China. Furthermore, we identified the major grazers that appear to directly affect the productivity of Spirulina cultures. Among twenty-three species that include 2 flagellates, 2 amoebae, 15 ciliates, and 4 rotifers, Brachionus plicatilis , Frontonia sp. and one unknown Heterolobosean amoeba appeared to be the most harmful to Spirulina due to their high density and ability to graze Spirulina . The similarity of the biodiversity and abundance of the microzooplankton was > 80% among two out of eight mass cultivation sites (C and D), while the remaining cultivation sites exhibited their own unique microzooplankton biodiversity characteristics. Redundancy analysis (RDA) showed that there was a positive relationship between harmful species of Brachionus plicatilis and salinity, while the other two harmful species of Heterolobosean amoeba and Frontonia sp. had a positive relationship with oxidation-reduction potential (ORP). As this is the first report to identify the major harmful microzooplankton species in commercial Spirulina farms, our study not only provides a theoretical basis for the relationship between environmental factors and biodiversity of harmful grazers but also lays a scientific foundation for developing effective monitoring and management strategies for commercial Spirulina farms. [ABSTRACT FROM AUTHOR]

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 mgFe/L (2.11 ± 0.13 mgFe/gbiomass for EDTA-FeNa, 3 H2O at 10 mgFe/L compared to 0.18 ± 0.13 for FeSO4,6H2O at 2 mgFe/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/m2/s. At 430 µmol/m2/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/m2/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.

Spirulina (Arthrospira) is an important microalga that can generate a variety of commercial products. A semi-continuous mode of cultivation is often employed in microalgal cultivation. The traditional view, however, has been that cultures with recycled medium are more likely to be contaminated by microzooplankton, which is regarded as one of the critical problems in mass algal cultivation. In this study, the relationship between the population dynamics of contaminants and the medium conditions was investigated in Spirulina cultures. Spirulina platensis was cultivated in three groups of raceway ponds: one with fresh culture medium, one with medium that had been recycled for a month, and the third with medium recycled for six months. The results showed that totally 13 species of microzooplankton were observed by light microscopy, and 42 operational taxonomic units (OTUs) of prokaryotic contaminants were detected using amplicon sequencing. Out of all the contaminants, Brachionus plicatilis and Euplaesiobystra hypersalinica were observed to be the most harmful species in Spirulina cultures, while Proteobacteria were the most commonly found non-Cyanobacteria OTUs. On the initial day, more species of microzooplankton were introduced to the cultures that had recycled medium (9 species) than to those that had fresh medium (5 species). By the end of the cultivation, the algal biomass in the fresh medium group was the highest (2.8 g L−1), being almost 5 times higher than in the other two groups (around 0.50 g L−1). Our results proved that Spirulina can grow the best with fresh medium and that the more the culture medium is recycled, the stronger the inhibition on the growth of microalgae and microzooplankton. In order to improve large-scale Spirulina production, it is necessary to both subject the recycled medium to appropriate treatment to reduce the presence of harmful predators and to find effective ways to control contaminants. • Spirulina grew better in fresh medium with the maximum biomass of 2.8 g L−1. • More contaminants were introduced to the cultures with recycled medium. • Inhibition effect on biological growth increased with the recycle times of medium. [ABSTRACT FROM AUTHOR]