Draft genome sequence of Arthrospira platensis C1 (PCC9438)

Arthrospira platensis is a cyanobacterium that is extensively cultivated outdoors on a large commercial scale for consumption as a food for humans and animals. It can be grown in monoculture under highly alkaline conditions, making it attractive for industrial production. Here we describe the complete genome sequence of A. platensis C1 strain and its annotation. The A. platensis C1 genome contains 6,089,210 bp including 6,108 protein-coding genes and 45 RNA genes, and no plasmids. The genome information has been used for further comparative analysis, particularly of metabolic pathways, photosynthetic efficiency and barriers to gene transfer.     

Factors indicating culture status during cultivation of Spirulina (Arthrospira) platensis

Factors indicating culture status of two Spirulina platensis strains were monitored in a batch mode cultivation for 36 days. Changing mode in all factors showed a common turning point, indicating shift of cell or culture status. Mean biomass productivity was highly sustained until day 22, chlorophyll a concentration peaked on day 22, pH value was >12 on day 22, coil number was abruptly shortened on day 22, and floating activity was sustained at greater than 79% after day 22, indicating that day 22 is a criterion reflecting phase-transfer in cell physiology in a batch culture system. Many of these changes may have been caused by increased pH, suggesting that pH control is essential for mass production of S. platensis. Fluctuations in floating activity were likely induced by the number of cellular gas vacuoles. Consequently, coil number per trichome and floating activity of S. platensis could readily act as simple indicators for determination of culture status or harvesting time of cells.     

Repeated fed-batch cultivation of Arthrospira (Spirulina) platensis using urea as nitrogen source

Arthrospira (Spirulina) platensis (Nordstedt) Gomont was autotrophically cultivated for biomass production in repeated fed-batch process using urea as nitrogen source, with the aim of making large-scale production easier, increasing cell productivity and then reducing the production costs. It was investigated the influence of the ratio of renewed volume to total volume (R), the urea feeding time (t_f) and the number of successive repeated fed-batch cycles on the maximum cell concentration (X_m), cell productivity (P_x), nitrogen-to-cell conversion yield (Y_x/n), maximum specific growth rate (μ_m) and protein content of dry biomass. The experimental results demonstrated that R = 0.80 and t_f = 6 d were the best cultivation conditions, being able to simultaneously ensure, throughout the three fed-batch cycles, the highest average values of three of the five responses (X_m = 2101 ± 113 mg L^?1, P_x = 219 ± 13 mg L^?1 d^?1 and Y_x/n = 10.3 ± 0.8 g g^?1).     

Simultaneous use of urea and potassium nitrate for Arthrospira (Spirulina) platensis cultivation

Urea has been considered as a promising alternative nitrogen source for the cultivation of Arthrospira platensis if it is possible to avoid ammonia toxicity; however, this procedure can lead to periods of nitrogen shortage. This study shows that the addition of potassium nitrate, which acts as a nitrogen reservoir, to cultivations carried out with urea in a fed-batch process can increase the maximum cell concentration (X(m) ) and also cell productivity (P(X) ). Using response surface methodology, the model indicates that the estimated optimum X(m) can be achieved with 17.3 mM potassium nitrate and 8.9 mM urea. Under this condition an X(m) of 6077 ± 199 mg/L and a P(X) of 341.5 ± 19.1 mg L(-1) day(-1) were obtained.     

鄂尔多斯高原碱湖的钝顶螺旋藻光合生理研究

鄂尔多斯高原碱湖的钝顶螺旋藻光合色素含量高低排列为藻胆素>叶绿素a>类胡萝卜素;各色素具有特定的吸收光谱,活体吸收光谱体现出了各色素的吸收;各色素的荧光发射主峰波长约长于活体的13￣35nm,相对荧光强度约是活体的11倍。其光合速率的日变化呈单峰曲线,13:00时达到最高;光补偿点为28￣30μmol.m-2.s-1;光饱和点为220￣235μmol.m-2.s-1;光合作用的最适温度为35℃。呼吸速率日变化随温度的升高呈缓慢上升的趋势。     

Application of Arthrospira (Spirulina) platensis biomass for silver removal from aqueous solutions

The cyanobacterium Arthrospira (Spirulina) platensis was used to study the process of silver biosorption. Effects of various parameters such as contact time, dosage of biosorbent, initial pH, temperature, and initial concentration of Ag(I) were investigated for a batch adsorption system. The optimal biosorption conditions were determined as pH 5.0, biosorbent dosage of 0.4 g, and initial silver concentration of 30 mg/L. Equilibrium adsorption data were analyzed by the Langmuir and Freundlich models – however, the Freundlich model provided a better fit to the experimental data. The kinetic data fit the pseudo-second-order model well, with a correlation coefficient of 0.99. The analysis of thermodynamic parameters (ΔG°, ΔH° and ΔS°) revealed that the adsorption process of silver ion by spirulina biomass was exothermic and spontaneous (ΔG° < 0), and exothermic (ΔH° < 0) process. The biosorption capacity of biomass A. platensis serves as a basis for the development of green technology for environmental remediation.     

Photosynthetic and respiratory electron transport in the alkaliphilic cyanobacterium Arthrospira (Spirulina) platensis

Photosynthetic and respiratory electron transport and their interplay with ion transport have been studied in Arthrospira platensis, a filamentous alkaliphilic cyanobacterium living in hypersaline lakes. As typical for alkaliphiles, A. platensis apparently does not maintain an outward positive pH gradient at its plasma membrane. Accordingly, sodium extrusion occurs via an ATP-dependent primary sodium pump, in contrast to the Na⁺/H⁺ antiport in most cyanobacteria. A. platensis is strongly dependent on sodium/bicarbonate symport for the uptake of inorganic carbon. Sodium extrusion in the presence of the Photosystem II inhibitor diuron indicates that a significant amount of ATP is supplied by cyclic electron transport around Photosystem I, the content of which in A. platensis is exceptionally high. Plastoquinol is oxidized by two parallel pathways, via the cytochrome b ₆ f complex and a putative cytochrome bd complex, both of which are active in the light and in the dark. This revised version was published online in August 2006 with corrections to the Cover Date.     

Growth inhibition of the cyanobacterium Spirulina (Arthrospira) platensis by 1.7 MHz ultrasonic irradiation

Ultrasonic waves of high frequency (1.7 MHz) and low intensity (0.6 W cm^–2) were employed to prevent cyanobacterial cells from growing fast and the effects of this growth inhibition were investigated. At least five minutes of ultrasonic irradiation was essential for effective inhibition. The growth rate of irradiated cells was reduced to 38.9% of the control during short-term culture. Longer exposure did not significantly enhance the inhibition. For a particular level of energy input, distributed ultrasonic exposure (more short intermittent exposures) was more effective in inhibiting growth than fewer, but longer exposures. For instance, the final biomass decreased to 30.1% of the control after ultrasonic irradiation for 4 minutes every 3 days, whereas it only decreased to 60% of the control with exposure for 12 minutes every 11 days. It is suggested that distributed ultrasonic irradiation is a practical method to prevent cyanobacterial cells from fast growth. A possible explanation for the inhibition is discussed in relation to cell structure, the absorption spectrum of intact cells, chlorophyll level and oxygen evolution.     

Purification and characterization of phycoferritin from the blue-green alga, Arthrospira (Spirulina) platensis

Phycoferritin from the nutritionally important blue-green alga Arthrospira platensis has been isolated, by application of conventional biochemical techniques. The molecular mass, yield, iron and total neutral carbohydrate contents of the purified protein were 470 kDa, 0.044 mg g⁻¹ of Arthrospira, 1.4 and 20%, respectively. The iron content was much lower when compared to bacterial and mammalian ferritins. The P: Fe ratio of Arthrospira phycoferritin was 1: 3.5, a value akin to bacterioferritins. Native gel-electrophoresis revealed the presence of isoforms. Subunit analysis by SDS-PAGE and Western blotting showed a protein subunit with an apparent molecular mass of 18 kDa. Oligomeric forms of the protein subunit were also present. The phycoferritin exhibited cross-reactivity with anti-pea seed ferritin suggesting phylogenetic relationship with that of higher plants. Carbohydrate analysis of phycoferritin by GC-MS revealed the presence of sugars such as galactose, glucose and mannose similar to that of mammalian ferritins. Interestingly, the analysis also revealed sugars such as rhamnose, xylose and talose, which has not been reported in the structure of ferritins. Except for very low histidine content in phycoferritin, the rest of the amino acid composition resembled to ferritins of other species. UV-visible spectral analysis of the phycoferritin revealed the presence of haem groups, a property characteristic of bacterioferritins. The fluorescence intensity of phycoferritin was higher than equine spleen ferritin. Circular dichroic spectra revealed a lower degree of helicity.     

Polyhydroxyalkanoates and pigments coproduction by Arthrospira (Spirulina) platensis cultivated in crude glycerol

Journal of Applied Phycology - Valorization of industrial waste as an alternative carbon source for microalgae mixotrophic cultivation and co-production of high-value compounds are strategies to...     

Photosynthetic performance of a helical tubular photobioreactor incorporating the cyanobacterium spirulina platensis

The photosynthetic performance of a helical tubular photobioreactor ("Biocoil"), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape (0.9 m high) with a 0.25-m(2)basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6-cm inner diameter (volume = 12.1 L). The inner surface of the cylinder (area = 1.32 m(2)) was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation(PAR, 400 to 700 nm) into the photobioreactor was 2920 kJ per day. An air-lift system ncorporating 4%CO(2) was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 g dry biomass per day [0.51 g . d biomass/L . day, or 5.44 g . d biomass/m(2)(inner surface of cylindrical shape)/day] which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO(2) was efficiently removed from the gaseous stream; monitoring the CO(2) the outlet and inlet gas streams showed a 70% removal of CO(2) from the inlet gas over an 8-h period with almost maximum growth rate. (c) 1995 John Wiley & Sons, Inc.     

Effect of Microalgae (Arthrospira platensis and Chlorella vulgaris) Addition on 3D Printed Cookies

Rheological and textural characteristics of cookie doughs were measured to characterise the effect of two microalgae biomasses additions (Arthrospira platensis and Chlorella vulgaris) in 3D printed cookies. The rheological characteristics determined the addition of microalgae lead to a greater mechanical resistance and a predominance of the elastic component ahead of the viscous component, this behaviour was confirmed by the textural analysis that showed a greater force for the extrusion of microalgae-enriched doughs. Besides, the influence of processing parameters, including filament diameter (26 and 27 mm) and layer height (1.3 and 1.5 mm), on the geometric accuracy of a 3D printed food structure made of cookie dough before and after baking process, was evaluated. The addition of microalgae biomass in dough, for 3D printed cookies, improves the printability in terms of dimensional properties, achieving 3D structures more stable and resistant to baking.

     

Induction of axenic culture of Arthrospira (Spirulina) platensis based on antibiotic sensitivity of contaminating bacteria

Arthrospira platensis SAG 21.99 and the isolated bacteria (Halomonas spp., Staphylococcus sp., etc.) from the culture of A. platensis SAG 21.99 were treated with five antibiotics to determine the minimal lethal concentrations. The combination of a washing step and a consecutive treatment with antibiotics, imipenem (100 μg ml⁻¹), neomycin (100 μg ml⁻¹) and cycloheximide (20 μg ml⁻¹), treatment step was highly effective in eliminating bacteria. An axenic culture of A. platensis SAG 21.99 could be induced within 3 days using this method. This technique is a simple and rapid method for obtaining axenic cultures of filamentous cyanobacteria.     

Effects of phosphorus concentration and light intensity on the biomass composition of Arthrospira (Spirulina) platensis

This paper presents the effects of various phosphorus concentrations (10, 50, 250 and 500 mg l(-1) K(2)HPO(4)) on the biomass production and composition of Arthrospira (Spirulina) platensis in relation to light intensity (24, 42 and 60 μE m(-2) s(-1)). The maximum biomass production was 3,592 ± 392 mg l(-1) and this was observed in 250 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1) light intensity after 32 days of cultivation. A maximum specific growth rate (μ(max)) of 0.55 d(-1) was obtained in 500 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1). The protein, lipid and chlorophyll contents of the biomass varied from 33.59 to 60.57 %, 5.34 to 13.33 % and 0.78 to 2.00 %, respectively. The most significant finding was that phosphorus limitation (10 mg l(-1) K(2)HPO(4)) caused a drastic increase of the carbohydrate content (59.64 %). The effect of phosphorus limitation on the carbohydrate content was independent of the light intensity. The accumulated carbohydrates are proposed to be used as substrate for biofuel generation via one of the appropriate biomass energy conversion technologies. Also, it was observed that phosphorus removal is a function of biomass density, phosphorus concentration and light intensity.     

Harvest of Arthrospira platensis from Lake Kossorom (Chad) and its household usage among the Kanembu

In 1997 a survey was conducted among the Kanembu whoharvest Arthrospira (Spirulina) from LakeKossorom in the Prefecture of Lac (Chad). Informationon the amount of Arthrospira harvested and thepreparation and use of dihé was obtained byinterviewing the women who daily gather around thelake for the harvesting. Dihé is obtained byfiltering and sun drying the algal biomass on thesandy shores of the lake. The semi-dried dihé is then cut into small squares and taken tothe villages, where the drying is completed on mats inthe sun. Dihé is mainly used to prepare la souce, a kind of fish or meat and vegetable broth.Part of the harvest is sold to local consumers or towholesalers, who trade the product in the markets ofMassakori, Massaquet and N'Djamena and also across theborder of the country. The local trading valueof the dihé annually harvested from LakeKossorom (about 40 t) amounts to more than US$100,000, which represents an important contributionto the economy of the area.     

Carbon limitation enhances CO2 concentrating mechanism but reduces trichome size in Arthrospira platensis (cyanobacterium)

Arthrospira species grow well under highly enriched inorganic carbon concentrations, but little is known on the effects of inorganic carbon (Ci) limitation on its physiological performance. When Arthrospira platensis D-0083 was grown in a modified medium without NaHCO₃ under ambient air of 380 ppm CO₂, its trichomes became disassembled while the growth and photosynthetic rates were severely reduced. Phycocyanin and allophycocyanin contents decreased but the carotenoid content increased under the Ci limitation. Compared with the cells grown in Zarrouk medium, the trichomes grown under the Ci limitation increased their photosynthetic apparent affinity for Ci by about 14 times but photochemical quenching capacity was reduced. It appeared that A. platensis increased its CO₂ concentrating mechanism by inducing HCO₃ ^? transporters and reducing the trichome size which increased filamentous surface to volume ratio.     

Partial characterization of extracellular polysaccharides produced by cyanobacterium Arthrospira platensis

In this study, the physico-chemical characteristics of extracellular polysaccharides (EPS) produced by Arthrospira platensis were evaluated. Elemental analysis and a bicinchoninic acid (BCA) reaction indicated that the EPS were heteropolysaccharides that contain carbohydrate (13%) and protein (55%) moieties. Analysis of the infrared spectrum and elemental analysis revealed the presence of a sulfate group (0.5%). The UV-visible spectrum showed high UV absorption at 190∼230 nm and a shoulder at 260∼280 nm. In addition, this spectrum indicated that EPS can form aggregates with mycosporine-like amino acids and/or scytonemin. Gas chromatography analysis of the carbohydrate portion of the EPS indicated that it was composed of seven neutral sugars: galactose (14.9%), xylose (14.3%), glucose (13.2%), frucose (13.2%), rhamnose (3.7%), arabinose (1%), and mannose (0.3%) and two uronic acids, galacturonic acid (13.5%) and glucuronic acid (0.9%).