ABSTRACT
Cyanobacteria are known to exhibit their efficiency in producing high concentrations of compounds of commercial value. Arthrospira is one such cyanobacterium which is considered as important source of protein (65%) and other nutrients. In present study, chemical mutagenesis using N-methyl-N-Nitro-nitrosoguanidine (NTG), a proven potent mutagen for cyanobacteria was used to bring stable and desirable alteration in Arthrospira platensis ARM 730. Three morphological mutants (G-1, G-2, and SF) were selected and characterized. The G-1 and G-2 were helical, more bluish in pigmentation than the wild type strain where G-1 also showed enlarged cell size. The SF mutant was an altered straight-filament having maximum biomass. Among three mutants, higher protein and phycocyanin contents were observed in G-1 and G-2 mutants whereas chlorophyll was less in these mutants as compared to wild type strain indicating change in the pigment ratio. Carotenoid content was higher in SF mutant as compared to wild type and other mutants. Variation in total sugar content was not observed in comparison to wild type strain. The analysis of amino acid spectrum of all the mutants and wild type showed significant increase in proline content. Overall, it is revealed from the results that G-1 and G-2 mutants showed higher biomass, phycocyanin, and protein contents in comparison to wild type which indicated their great potential to be used in food and pharmaceutical industries.
Subject(s)
Bacterial Proteins/metabolism , Mutation , Phycocyanin/metabolism , Spirulina/isolation & purification , Spirulina/metabolism , Methylnitronitrosoguanidine/metabolism , Mutagenesis , Mutagens/metabolism , Spirulina/cytology , Spirulina/growth & developmentABSTRACT
CONTEXT: Algae have gained importance in cosmeceutical product development due to their beneficial effects on skin health and therapeutical value with bioactive compounds. Spirulina platensis Parachas (Phormidiaceae) is renowned as a potential source of high-value chemicals and recently used in skincare products. OBJECTIVE: This study develops and evaluates skin creams incorporated with bioactive S. platensis extract. MATERIALS AND METHODS: Spirulina platensis was cultivated, the aqueous crude extract was prepared and in vitro cytotoxicity of S. platensis extract in the range of 0.001-1% concentrations for 1, 3 and 7 d on HS2 keratinocyte cells was determined. Crude extracts were incorporated in skin cream formulation at 0.01% (w/w) concentration and in vitro wound healing and genotoxicity studies were performed. Immunohistochemical staining was performed to determine the collagen activity. RESULTS: 0.1% S. platensis extract exhibited higher proliferation activity compared with the control group with 198% of cell viability after 3 d. Skin cream including 1.125% S. platensis crude extract showed enhanced wound healing effect on HS2 keratinocyte cell line and the highest HS2 cell viability % was obtained with this concentration. The micronucleus (MN) assay results indicated that S. platensis extract incorporated creams had no genotoxic effect on human peripheral blood cells. Immunohistochemical analysis showed that collagen 1 immunoreactivity was improved by increased extract concentration and it was strongly positive in cells treated with 1.125% extract incorporated skin cream. CONCLUSIONS: The cell viability, wound healing activity and genotoxicity results showed that S. platensis incorporated skin cream could be of potential value in cosmeceutical and biomedical applications.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Antioxidants/pharmacology , Biological Products/pharmacology , Keratinocytes/drug effects , Skin Cream/pharmacology , Spirulina/chemistry , Wound Healing/drug effects , Anti-Inflammatory Agents, Non-Steroidal/adverse effects , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Antioxidants/adverse effects , Antioxidants/chemistry , Biological Products/adverse effects , Biological Products/chemistry , Cell Line , Cell Movement/drug effects , Cell Proliferation/drug effects , Cell Survival/drug effects , Cells, Cultured , Collagen/metabolism , Drug Evaluation, Preclinical , Fibroblasts/cytology , Fibroblasts/drug effects , Fibroblasts/metabolism , Humans , Keratinocytes/cytology , Keratinocytes/metabolism , Kinetics , Lymphocytes/cytology , Lymphocytes/drug effects , Microalgae/chemistry , Micronucleus Tests , Skin Cream/adverse effects , Spirulina/cytology , Spirulina/growth & developmentABSTRACT
Efficient cryopreservation conditions for the edible alkalophilic cyanobacterium Arthrospira (Spirulina) platensis were investigated using a model strain A. platensis NIES-39. As a result, it was found that more than 60% of cells were viable upon thawing, when they had been frozen at a cooling rate of approximately -1 °C min(-1) in the presence of 10% (v/v) dimethyl sulfoxide. Further examination with other Arthrospira strains showed that many of them had strain-dependent optimal conditions for cryopreservation. For example, the best freezing conditions for A. platensis SAG 21.99 were snap-freezing in liquid nitrogen in the presence of 5% (v/v) dimethyl sulfoxide, while they were slow cooling at approximately -1 °C min(-1) in the presence of 10% (v/v) methanol for A. platensis NIES-46, NIES-2308 and UTEX 1926. The variety of successful cryopreservation conditions presented in this study is useful when attempting to cryopreserve various Arthrospira strains.
Subject(s)
Cryopreservation/methods , Spirulina/cytology , Cell Proliferation , Cell Survival , Species SpecificityABSTRACT
In this study, the effect of Mougeotia nummuloides and Spirulina major on Vero cells (African green monkey kidney), C6 cells (rat brain tumor cells) and HeLa cells (human uterus carcinoma) was investigated in vitro. The antiproliferative effect of the methanol extract of M. nummuloides and S. major compared with 5-fluorourasil (5-FU) and cisplatin was tested at various concentrations using the BrdU Cell Proliferation ELISA. Both M. nummuloides and S. major extracts significantly inhibited the proliferation of Vero, HeLa and C6 cancer cell lines with IC50 and IC75 values. The M. nummuloides extract exhibited higher activity than 5-FU and cisplatin on Vero and C6 cells at high concentrations. The S. major extract revealed better antifproliferative activity than standards against Vero cells at 500 µg/mL. The compounds of methanol extracts were determined by GC-MS after the silylation process. Trehalose, monostearin and 1-monopalmitin were detected as major products in the M. nummuloides extract where as in the S. major extract; monostearin, 1-monopalmitin and hexyl alcohol were the main constituents.
Subject(s)
Biological Products/pharmacology , Cell Proliferation/drug effects , Mougeotia/chemistry , Spirulina/chemistry , Animals , Biological Products/chemistry , Biological Products/isolation & purification , Cell Line, Tumor , Cells, Cultured , Chlorocebus aethiops , Gas Chromatography-Mass Spectrometry , Glycerides/chemistry , Glycerides/isolation & purification , Glycerides/pharmacology , HeLa Cells , Humans , Inhibitory Concentration 50 , Methanol/chemistry , Molecular Structure , Mougeotia/cytology , Neoplasms/pathology , Rats , Spirulina/cytology , Trehalose/chemistry , Trehalose/isolation & purification , Trehalose/pharmacology , Vero CellsABSTRACT
Inducing an axenic culture of the edible cyanobacterium Arthrospira (Spirulina) platensis using differential filtration alone is never successful; thus, it has been thought that, in non-axenic cultures, a portion of contaminating bacteria is strongly associated with Arthrospira cells. However, examination of the behavior of these bacteria during filtration revealed that they were not associated with Arthrospira cells but with aggregates of exopolysaccharides present in the medium away from the Arthrospira cells. Based on this finding, a rapid and reliable method for preparing axenic trichomes of A. platensis was established. After verifying the axenicity of the resulting trichomes on enriched agar plates, they were individually transferred to fresh sterile medium using a handmade tool, a microtrowel, to produce axenic cultures. With this technique, axenic cultures of various A. platensis strains were successfully produced. The technique described in this study is potentially applicable to a wider range of filamentous cyanobacteria.
Subject(s)
Axenic Culture/methods , Heterotrophic Processes , Polysaccharides, Bacterial/metabolism , Spirulina/growth & development , Spirulina/metabolism , Extracellular Space/metabolism , Filtration , Spirulina/cytologyABSTRACT
This study dealt with the influence of both the feeding time and light intensity on the fed-batch culture of the cyanobacterium Spirulina (Arthrospira) platensis using ammonium chloride as a nitrogen source. For this purpose, a 2(2) plus star central composite experimental design combined with response surface methodology was employed, and the maximum cell concentration (X(m)), the cell productivity (P(X)), and the yield of biomass on nitrogen (Y(X/N)) were selected as the response variables. The optimum values of X(m) (1,833 mg L(-1)) and Y(X/N) (5.9 g g(-1)) estimated by the model at light intensity of 13 klux and feeding time of 17.2 days were very close to those obtained experimentally under these conditions (X(m) = 1,771 +/- 41 mg L(-1); Y(X/N) = 5.7 +/- 0.17 g g(-1)). The cell productivity was a decreasing function of the ammonium chloride feeding time and a quadratic function of the light intensity. The protein and lipid contents of dry biomass collected at the end of cultivations were shown to decrease with increasing light intensity.
Subject(s)
Ammonium Chloride/metabolism , Bioreactors/microbiology , Cell Culture Techniques/methods , Models, Biological , Spirulina/physiology , Spirulina/radiation effects , Cell Proliferation/radiation effects , Cell Survival/drug effects , Computer Simulation , Dose-Response Relationship, Radiation , Radiation Dosage , Spirulina/cytology , Time FactorsABSTRACT
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 microg ml(-1)), neomycin (100 microg ml(-1)) and cycloheximide (20 microg 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.
Subject(s)
Anti-Bacterial Agents/administration & dosage , Cell Culture Techniques/methods , Spirulina/classification , Spirulina/drug effects , Dose-Response Relationship, Drug , Species Specificity , Spirulina/cytologyABSTRACT
Internal loop airlift and bubble column photobioreactors (PBR) were compared with respect to their performances during cultivation of Artrospira platensis (Spirulina platensis). Culture conditions were kept the same and different parameters were examined through the experiments. It was observed that a higher dry biomass weight and chlorophyll-a concentration was obtained in the airlift PBR yielding a maximum growth rate of 0.45 day(-1), while 0.33 day(-1) was reached in the bubble column PBR. Subsequently, a 17-day of production was carried out in the selected PBR to fully determine the performance of the PBR. Maximum growth rate of 0.47 day(-1) was reached during long term cultivation.
Subject(s)
Bioreactors , Spirulina/cytology , Biomass , Chlorophyll/metabolism , Hydrogen-Ion Concentration , Spectrum AnalysisABSTRACT
In this study, effect of different 2,4 -dichlorophenoxyacetic acid (2,4-D) concentrations (0.0, 9.10(-5), 9.10(-4), 9.10(-3) and 9.10(-2) mM) on growth rate, content of protein and chlorophyll-a in Chlorella vulgaris and Spirulina platensis cells was investigated. The most stimulatory effect on growth rate, protein and pigment ratio of C. vulgaris and S. platensis was observed at 9.10(-4) mM concentrations of 2,4-D. The results show that low concentrations of 2,4-D have hormonal effect due to being a synthetic auxin. Cell number protein and pigment rates were inhibited at 9.10(-2) mM concentration in C. vulgaris. Such parameters were inhibited in S. platensis, both at 9.10(-3) and 9.10(-2) mM 2,4-D concentrations. This is due to herbicidal effect of high concentrations of 2,4-D. S. platensis was found to be more sensitive than S. vulgaris to 2,4-D applications. The use of algae as bio-indicators in herbicide contaminated fresh water habitats, was discussed.
Subject(s)
2,4-Dichlorophenoxyacetic Acid/toxicity , Chlorella vulgaris/drug effects , Chlorophyll/metabolism , Herbicides/toxicity , Nuclear Proteins/metabolism , Spirulina/drug effects , Water Pollutants, Chemical/toxicity , 2,4-Dichlorophenoxyacetic Acid/metabolism , Chlorella vulgaris/cytology , Chlorella vulgaris/growth & development , Chlorella vulgaris/metabolism , Chlorophyll A , Dose-Response Relationship, Drug , Fresh Water , Herbicides/metabolism , Kinetics , Pigments, Biological/antagonists & inhibitors , Pigments, Biological/metabolism , Spirulina/cytology , Spirulina/growth & development , Spirulina/metabolism , Water Pollutants, Chemical/metabolismABSTRACT
Morphological transformations in primitive organisms have long been observed; however, its biomechanical roles are largely unexplored. In this study, we investigate the structural advantages of dimorphism in Arthrospira platensis, a filamentous multicellular cyanobacterium. We report that helical trichomes, the default shape, have a higher persistence length (Lp), indicating a higher resistance to bending or a large value of flexural rigidity (kf), the product of the local cell stiffness (E) and the moment of inertia of the trichomes' cross-section (I). Through Atomic Force Microscopy (AFM), we determined that the E of straight and helical trichomes were the same. In contrast, our computational model shows that I is greatly dependent on helical radii, implying that trichome morphology is the major contributor to kf variation. According to our estimation, increasing the helical radii alone can increase kf by 2 orders of magnitude. We also observe that straight trichomes have improved gliding ability, due to its structure and lower kf. Our study shows that dimorphism provides mechanical adjustability to the organism and may allow it to thrive in different environmental conditions. The higher kf provides helical trichomes a better nutrient uptake through advection in aquatic environments. On the other hand, the lower kf improves the gliding ability of straight trichomes in aquatic environments, enabling it to chemotactically relocate to more favorable territories when it encounters certain environmental stresses. When more optimal conditions are encountered, straight trichomes can revert to their original helical form. Our study is one of the first to highlight the biomechanical role of an overall-shape transformation in cyanobacteria.
Subject(s)
Cell Shape/physiology , Spirulina/cytology , Spirulina/metabolism , Biochemical Phenomena , Biological Transport/physiology , Biomechanical Phenomena , Biophysics , Computer Simulation , Cyanobacteria/cytology , Cyanobacteria/metabolism , Cyanobacteria/physiology , Trichomes/physiologyABSTRACT
Spirulina is distinguished from other cyanobacteria by its spiral morphology; however, this cyanobacterium has frequently been observed with a linear morphology in laboratory and industrial conditions. In our laboratory conditions, the simultaneously presence of the linear and spiral forms has also been observed. In the present study, the two forms of S. platensis C1 were separated and grown as axenic cultures in order to study the proteins that were differentially expressed in the soluble and insoluble protein fractions of the spiral and the linear forms. Two dimensional-differential gel electrophoresis (2D-DIGE) was performed to separate differentially expressed proteins that were subsequently identified by mass spectrometry. The differentially expressed proteins suggested two points. First, the morphological change is possibly induced by various environmental stresses such as oxygen level, carbon dioxide level, nutrient availability, and light. Second, the change of cell-shape might be a result of the change in a cell shape determination mechanism. Thus, this study is the first to show evidence at the protein level that may explain this morphological transformation in Spirulina.
Subject(s)
Bacterial Proteins/metabolism , Morphogenesis , Spirulina/growth & development , Spirulina/metabolism , Bacterial Proteins/analysis , Electrophoresis, Gel, Two-Dimensional , Proteomics , Spirulina/cytologyABSTRACT
The interactive effects of light intensity and NaCl concentration were investigated for Spirulina two-step cultivation process using Full Factorial Design. In the experiment interval, light intensity had no effect while the NaCl concentration had significant effect on the enhancement of extracellular polymeric substances (EPS) production. Interestingly, results revealed a significant negative interaction between light and NaCl concentration indicating that high NaCl concentration (40gL-1) and low light intensity (10µmol photons m-2s-1) enhanced the EPS production. Under these conditions, EPS production reached a maximum of 1.02gg-1 of biomass (dry weight), which is 1.67-folds greater than EPS content under optimal growth conditions (10µmol photons m-2s-1, 1gL-1, 30°C). Desalting and deproteinezation steps of EPS were efficient to obtain polysaccharides (PS) with high carbohydrate (67.3±1.1%), low soluble proteins (5.14±0.32%), ash (5.85±0.71%) and sulfate (2.42±0.12%) contents. Rheological studies of PS at different concentrations (1%, 2.5% and 5%) revealed that the viscosity of the solution increased with the increase of PS concentration. In addition, PS exhibited a non Newtonian shear-thinning nature, a predominant gel-like behavior and a good resistance to consecutive heating-cooling cycles. The adopted process could be, then, a promising and economic strategy to enhance EPS production and extract polysaccharides with interesting rheological properties.
Subject(s)
Extracellular Space/metabolism , Polysaccharides/biosynthesis , Polysaccharides/chemistry , Spirulina/cytology , Spirulina/metabolism , Biomass , Culture Techniques , Industry , Kinetics , Rheology , Spirulina/growth & development , ViscosityABSTRACT
Non-renewable sources that will end with time are the largest part of world energy consumption, which emphasizes the necessity to develop renewable sources of energy. This necessity has created opportunities for the use of microalgae as a biofuel. The use of microalgae as a feedstock source for bioethanol production requires high yields of both biomass and carbohydrates. With mixotrophic cultures, wastewater can be used to culture algae. The aim of the study was to increase the carbohydrate content in the microalgae Spirulina with the additions of residues from the ultra and nanofiltration of whey protein. The nutrient deficit in the Zarrouk medium diluted to 20% and the addition of 2.5% of both residue types led to high carbohydrate productivity (60 mg L(-1) d(-1)). With these culture conditions, the increase in carbohydrate production in Spirulina indicated that the conditions were appropriate for use with microalgae as a feedstock in the production of bioethanol.
Subject(s)
Biofuels , Biotechnology/methods , Carbohydrates/biosynthesis , Microalgae/metabolism , Spirulina/metabolism , Biomass , Biotechnology/instrumentation , Cell Culture Techniques/methods , Culture Media/chemistry , Microalgae/chemistry , Microalgae/cytology , Spirulina/chemistry , Spirulina/cytology , Ultrafiltration , Wastewater , Whey Proteins/metabolismABSTRACT
The C-phycocyanin generated in blue-green algae Arthrospira platensis is gaining commercial interest due to its nutrition and healthcare value. In this study, the light intensity and initial biomass concentration were manipulated to improve cell growth and C-phycocyanin production of A.platensis in batch cultivation. The results show that low light intensity and high initial biomass concentration led to increased C-phycocyanin accumulation. The best C-phycocyanin productivity occurred when light intensity and initial biomass concentration were 300µmol/m(2)/s and 0.24g/L, respectively. The fed-batch cultivation proved to be an effective strategy to further enhance C-phycocyanin production of A.platensis. The results indicate that C-phycocyanin accumulation not only requires nitrogen-sufficient condition, but also needs other nutrients. The highest C-phycocyanin content (16.1%), production (1034mg/L) and productivity (94.8mg/L/d) were obtained when using fed-batch strategy with 5mM medium feeding.
Subject(s)
Batch Cell Culture Techniques/methods , Phycocyanin/biosynthesis , Spirulina/growth & development , Spirulina/metabolism , Light , Nitrogen/metabolism , Phototrophic Processes , Spirulina/cytologyABSTRACT
Using an analogy with fed-batch heterotrophic growth, the algal photoautotrophic yield Φ(DW) (in grams of dry weight biomass synthesized per micromole of absorbed photons) was derived from the algae batch growth behavior in nutrient-replete medium. At known levels of incident light, the yield Φ(DW) enables the estimate of a maximum productivity, and is therefore critical to compare and select algal cultures and growth conditions for large-scale production. The algal culture maximum growth rate was shown to be an unreliable indicator of autotrophic biomass yield. The developed carbonate addition method (carbonate addition, neutralization, and sealing) alleviated carbon limitations otherwise seen in aerated batch cultures, leading to two to five fold higher yield estimates. The fully defined FLX growth medium with variable ionic strengths (FLX1-100) supported excellent growth in most cultures tested. The chosen experimental methods and versatile FLX medium proved well-suited for small sample volumes and a high number of samples.
Subject(s)
Biomass , Cyanobacteria/metabolism , Autotrophic Processes , Cyanobacteria/classification , Photosynthesis/physiology , Spirulina/cytology , Spirulina/metabolismABSTRACT
Previous work demonstrated that a mixture of NH(4)Cl and KNO(3) as nitrogen source was beneficial to fed-batch Arthrospira (Spirulina) platensis cultivation, in terms of either lower costs or higher cell concentration. On the basis of those results, this study focused on the use of a cheaper nitrogen source mixture, namely (NH(4))(2)SO(4) plus NaNO(3), varying the ammonium feeding time (T=7-15 days), either controlling the pH by CO(2) addition or not. A. platensis was cultivated in mini-tanks at 30°C, 156 µmol photons m(-2) s(-1), and starting cell concentration of 400 mg L(-1), on a modified Schlösser medium. T=13 days under pH control were selected as optimum conditions, ensuring the best results in terms of biomass production (maximum cell concentration of 2911 mg L(-1), cell productivity of 179 mg L(-1)d(-1) and specific growth rate of 0.77 d(-1)) and satisfactory protein and lipid contents (around 30% each).
Subject(s)
Ammonium Sulfate/pharmacology , Biomass , Spirulina/drug effects , Spirulina/growth & development , Hydrogen-Ion Concentration/drug effects , Spirulina/cytology , Time FactorsABSTRACT
Cyanobacteria have many unexploited potential for natural products with a huge variability in structure and biological activity. Their products are species specific and substrate+growth condition specific. Under stress conditions they are reported to produce biopolymers like EPS and PHA, which can be produced extracellularly and intracellularly, respectively. Polyhydroxyalkanoates are polymers of biological origin, they are also capable of being completely broken down to water and carbon dioxide by microorganisms found in a wide range of environments, such as soil, water, and sewage. We have studied marine cyanobacteria Spirulina subsalsa from Veraval coast, Gujarat, India, producing PHA under increased sodium chloride (NaCl) concentration (5% enhancement to the ASNIII medium), The biopolymer was chemically characterized through FTIR, NMR, TGA, and DSC. The present study shows increased PHA accumulation in S. subsalsa by twofold increased NaCl concentration in the growth media.
Subject(s)
Polyhydroxyalkanoates/biosynthesis , Seawater/microbiology , Spirulina/metabolism , Calorimetry, Differential Scanning , India , Magnetic Resonance Spectroscopy , Oxazines , Polyhydroxyalkanoates/chemistry , Sodium Chloride/pharmacology , Spectroscopy, Fourier Transform Infrared , Spirulina/cytology , Spirulina/growth & development , Spirulina/ultrastructure , Staining and Labeling , ThermogravimetryABSTRACT
The prospects of utilizing pretreated seawater for the culture of Arthrospira (Spirulina) platensis was evaluated under laboratory conditions with three seawater media and a control: (1) Zarrouk media (freshwater-control) (2) seawater media SW 1 (3) seawater media SW2 and (4) seawater media SW 3. The relative performance of these media were investigated with respect to their biomass production, pigment production (phycocyanin, lutein and betacarotene), and biochemical composition. A. platensis grown in media SW 2 had a biomass production (2.99+/-0.145 g L(-1)) comparable to that of control media (3.114+/-0.085 g L(-1)); highest specific growth rate (0.255 d(-1)) and lowest doubling time (2.720 days). Phycocyanin content of the cells grown in seawater media SW 3(81.85%) was closer to that of control. Similarly the purity ratio of phycocyanin produced from cells grown in seawater media SW 3 and control were closer to 4, while the phycocyanin obtained from cells grown in other two media exhibited lower purity ratios due to accumulation of lower molecular weight carbohydrates. The phycocyanin/Chl-a ratio and the betacarotene/Chl-a ratio of the cells grown in seawater media were higher than control. The lutein content of A. platensis cells grown in seawater media SW 2 was higher than that of control. The cells grown in seawater media had a slightly modified biochemical composition than the control with a higher carbohydrate and lower protein content. All the three seawater based media with fewer chemicals than the control (Zarrouk media) supported the growth of A. platensis as good as the control.
Subject(s)
Cell Culture Techniques/methods , Pigments, Biological/biosynthesis , Seawater/microbiology , Spirulina/cytology , Spirulina/metabolism , Biomass , Carbohydrates/analysis , Chlorophyll/metabolism , Chlorophyll A , Culture Media/pharmacology , Elements , Lipids/analysis , Phycocyanin/metabolism , Spirulina/drug effects , Spirulina/growth & development , Time Factors , beta Carotene/metabolismABSTRACT
Arthrospiraplatensis was cultivated in minitanks at 13 klux, using a mixture of KNO(3) and NH(4)Cl as nitrogen source. Fed-batch daily supply of NH(4)Cl at exponentially-increasing feeding rate allowed preventing ammonia toxicity and nitrogen deficiency, providing high maximum cell concentration (X(m)) and high-quality biomass (21.85 mg chlorophyll g cells(-1); 20.5% lipids; 49.8% proteins). A central composite design combined to response surface methodology was utilized to determine the relationships between responses (X(m), cell productivity and nitrogen-to-cell conversion factor) and independent variables (KNO(3) and NH(4)Cl concentrations). Under optimum conditions (15.5mM KNO(3); 14.1mM NH(4)Cl), X(m) was 4327 mg L(-1), a value almost coincident with that obtained with only 25.4mM KNO(3), but more than twice that obtained with 21.5mM NH(4)Cl. A 30%-reduction of culture medium cost can be estimated when compared to KNO(3)-batch runs, thus behaving as a cheap alternative for the commercial production of this cyanobacterium.
Subject(s)
Ammonium Chloride/pharmacology , Biotechnology/methods , Nitrates/pharmacology , Nitrogen/pharmacology , Potassium Compounds/pharmacology , Spirulina/drug effects , Spirulina/growth & development , Ammonia/analysis , Biomass , Carbon/pharmacology , Chlorophyll/analysis , Hydrogen-Ion Concentration/drug effects , Lipids/analysis , Multivariate Analysis , Nitrates/analysis , Proteins/analysis , Regression Analysis , Spirulina/cytology , Time FactorsABSTRACT
Monomerization and trimerization of photosystem I (PSI) in cyanobacteria are reversible to response to light switched off and on, which leads to "energy spillover" to regulate excitation of the two photosystems in balance. Considering that PSI is a trans-membrane protein embedded in thylakoid membranes, the monomerization or trimerization must involve a movement of PSI in the membranes. In this work, the mobility of PSI was demonstrated by dependence of the monomerization and trimerization on temperature for intact Spirulina platensis cells undergoing a light-to-dark or a dark-to-light transition. Based on the characteristic absorbance of monomers and trimmers, it confirms that both monomerization and trimerization are temperature-sensitive. The relative populations of the monomers and trimmers are invariable above the phase transition temperature (T (PT)) while directly proportional to temperature below T (PT). On the other hand, the rate to reach the equilibrium population is proportional to temperature above T (PT) but invariable below T (PT). The PSI mobility and the temperature-dependent population are contrary to those of plastoquinone (PQ) molecules because PSI is a trans-membrane protein while PQ molecules are small diffusive electron carriers in thylakoid membranes as well as their distinctive sizes and environments. The less monomerization of PSI but the invariable time constant at lower temperature below T (PT) may be due to that accumulation of the reduced PQ molecules results in decrease of the stromal-side H(+) concentration which is a driving force of PSI monomerization.