Assessing the Impact of Hexavalent Chromium (Cr VI) at Varied Concentrations on Spirulina platensis for Growth, Metal Sorption, and Photosynthetic Responses.

Spirulina platensis, a photosynthetic cyanobacterium, has garnered attention for its potential role in environmental remediation due to its ability to absorb and metabolize toxic heavy metals. Understanding its response toward toxicity of one of the most common contaminants, Cr(VI) is crucial for assessing its efficacy in bioremediation efforts. This study aims to investigate the physiological and biochemical responses of Spirulina platensis to varying concentrations of Cr(VI) from 0.5 to 5 ppm, shedding light on its potential as a bioindicator for environmental contamination and its suitability for bioremediation purposes. The impact of Cr(VI) on cell density, biosorption, pigment levels, nutrient content, fluorescence response, and photosynthetic efficiency was examined. The study revealed a gradual reduction in cell density, biomass production, and biosorption efficiency with increasing Cr(VI) concentrations. Pigment levels, carbohydrate, protein, and lipid content showed significant decreases, indicating physiological stress. Fluorescence response and photosynthetic efficiency were also adversely affected, suggesting alterations in electron transfer dynamics. A threshold for chromium toxicity was observed at 0.5 ppm, beyond which significant physiological disturbances occurred. This investigation highlights the sensitivity of Spirulina platensis to Cr(VI) toxicity and its potential as a bioindicator for heavy metal contamination. Metal sorption was highest in 0.5 ppm Cr(VI) with 56.56% removal. Notably, at lower concentrations, Cr(VI) acted as an intermediate electron acceptor, enhancing the electron transport chain and potentially increasing biomass under controlled conditions. The findings underscore the importance of understanding the mechanisms underlying heavy metal stress in microalgae for effective environmental remediation strategies. The research highlights the dual role of chromium(VI) in influencing S. platensis, depending on the concentration, and underscores the importance of understanding metal ion interactions with photosynthetic organisms for potential applications in bioremediation.

Enhancing french basil growth through synergistic Foliar treatment with copper nanoparticles and Spirulina sp.

BACKGROUND: This study investigates a novel idea about the foliar application of nanoparticles as nanofertilizer combined with a natural stimulant, blue-green algae Spirulina platensis L. extract, as a bio-fertilizer to achieve safety from using nanoparticles for enhancement of the growth and production of the plant. Thus, this experiment aimed to chemically synthesize copper nanoparticles via copper sulfate in addition to evaluate the impact of CuNPs at 500, 1000, and 1500 mg/L and the combination of CuNPs with or without microalgae extract at 0.5, 1, and 1.5 g/L on the morphological parameters, photosynthetic pigments accumulation, essential oil production, and antioxidant activity of French basil. RESULTS: The results revealed that foliar application of CuNPs and its interaction with spirulina extract significantly increased growth and yield compared with control, the treatments of 1000 and 1500 mg/L had less impact than 500 mg/L CuNPs. Plants treated with 500 mg/L CuNPs and 1.5 g/L spirulina extract showed the best growth and oil production, as well as the highest accumulation of chlorophylls and carotenoids. The application of CuNPs nanofertilizer caused a significant increase in the antioxidant activity of the French basil plant, but the combination of CuNPs with spirulina extract caused a decrease in antioxidant activity. CONCULOSION: Therefore, foliar application of natural bio-fertilizer with CuNPsis necessary for obtaining the best growth and highest oil production from the French basil plant with the least damage to the plant and the environment.

The impact of polystyrene nanoplastics (PSNPs) on physiological and biochemical parameters of the microalgae Spirulina platensis.

Nanoplastics, as emerging pollutants, have harmful effects on living organisms and the environment, the mechanisms and extent of which remain unclear. Microalgae, as one of the most important biological groups in the food chain and sensitive environmental indicators to various pollutants, are considered a suitable option for investigating the effects of nanoplastics. In this study, the effects of polystyrene nanoplastics on the growth rate, dry weight, chlorophyll a and carotenoid levels, proline, and lipid peroxidation in the Spirulina platensis were examined. Three concentrations of 0.1, 1, and 10 mg L-1 of PSNPs were used alongside a control sample with zero concentration, with four repetitions in one-liter containers for 20 days under optimal temperature and light conditions. Various analyses, including growth rate, dry weight, proline, chlorophyll a and carotenoid levels, and lipid peroxidation, were performed. The results indicated that exposure to PSNP stress led to a significant decrease in growth rate, dry weight, and chlorophyll a and carotenoid levels compared to the control sample. Furthermore, this stress increased the levels of proline and lipid peroxidation in Spirulina platensis. Morphological analysis via microscopy supported these findings, indicating considerable environmental risks associated with PSNPs.

The extracellular polymeric substances (EPS) accumulation of Spirulina platensis responding to Cadmium (Cd2+) exposure.

Spirulina platensis can secrete extracellular polymeric substances (EPS) helping to protect damage from stress environment, such as cadmium (Cd2+) exposure. However, the responding mechanism of S. platensis and the secreted EPS to exposure of Cd2+ is still unclear. This research focuses on the effects of Cd2+ on the composition and structure of the EPS and the response mechanism of EPS secretion from S. platensis for Cd2+ exposure. S. platensis can produce 261.37 mg·g-1 EPS when exposing to 20 mg·L-1 CdCl2, which was 2.5 times higher than the control group. The S. platensis EPS with and without Cd2+ treatment presented similar and stable irregularly fibrous structure. The monosaccharides composition of EPS in Cd2+ treated group are similar with control group but with different monosaccharides molar ratios, especially for Rha, Gal, Glc and Glc-UA. And the Cd2+ treatment resulted in a remarkable decline of humic acid and fulvic acid content. The antioxidant ability of S. platensis EPS increased significantly when exposed to 20 mg·L-1 CdCl2, which could be helpful for S. platensis protecting damage from high concentration of Cd2+. The transcriptome analysis showed that sulfur related metabolic pathways were up-regulated significantly, which promoted the synthesis of sulfur-containing amino acids and the secretion of large amounts of EPS.

Spirulina platensis en el tratamiento de la obesidad y de algunas de sus consecuencias / Spirulina platensis in the Treatment of Obesity and some of its Consequences

Introducción: La Spirulina platensis constituye un sustancial reservorio de nutrientes y de alimentos funcionales con un bajo contenido de calorías. Aunque en la literatura se mencionan varias cualidades benéficas, una de ellas es aumentar la sensación de saciedad, lo que abre la posibilidad de ser empleada en la prevención y tratamiento de la obesidad y de algunas de sus consecuencias. Objetivo: Describir el papel de la Spirulina platensis en el tratamiento de la obesidad y de algunas de sus consecuencias. Métodos: Se realizó una búsqueda de literatura relevante sobre el tema en el primer cuatrimestre de 2020. Se utilizaron como buscadores de información científica: Pubmed, Scielo, Google y Google Académico. La estrategia de búsqueda incluyó los siguientes términos como palabras clave: Espirulina; Spirulina platensis; Obesidad; Exceso de peso. Se evaluaron artículos de revisión, de investigación y páginas Web que, en general, tenían menos de 10 años de publicados, en idioma español, portugués e inglés, y que hicieran referencia específicamente al tema de estudio a través del título. Fueron excluidos los artículos que no cumplieron con estas condiciones. Esto permitió el estudio de 75 referencias bibliográficas, de las cuales 51 se citaron en el presente artículo. Conclusiones: La Spirulina platensis representa una opción como suplemento nutraceútico y funcional, con valor preventivo y coadyuvante en el tratamiento de la obesidad y de algunas de sus consecuencias, al menos a corto plazo(AU)

Introduction: Spirulina platensis is a substantial reservoir of functional foods and nutrients with low calorie content. Although several beneficial qualities are mentioned in the scientific literature, one of them is to increase the feeling of satiety, which opens the possibility of being used for preventing and treating obesity, as well as some of its consequences. Objective: To describe the role of Spirulina platensis for treating obesity and some of its consequences. Methods: A search of relevant literature on the subject was carried out in the first four months of 2020. The following scientific information search engines were used: Pubmed, Scielo, Google and Google Scholar. The search strategy included the following terms as keywords: espirulina [spirulina], Spirulina platensis, obesidad [obesity], exceso de peso [overweight]. Review articles, research articles and Web pages were assessed, which, in general, had been published within less than ten years, in Spanish, Portuguese and English, and which made specific reference to the study topic through their titles. Articles that did not meet these conditions were excluded. This allowed the study of 75 bibliographic references, of which 51 were cited in this article. Conclusions: Spirulina platensis is an option as a nutraceutical and functional supplement, with preventive and coadjutant value for the treatment of obesity and some of its consequences, at least in the short term(AU)

Green Synthesis of Selenium Nanoparticles by Cyanobacterium Spirulina platensis (abdf2224): Cultivation Condition Quality Controls.

Selenium nanoparticles (SeNPs) are well-known bioactive compounds. Various chemical and biological methods have been applied to SeNP synthesis. Spirulina platensis is a widely used blue-green microalgae in various industries. In this study, the biosynthesis of SeNPs using sodium selenite and Spirulina platens has been developed. The SeNP synthesis was performed at different cultivation condition including pH and illumination schedule variation. The SeNPs were characterized by FT-IR, XRD, size, and zeta potential measurements, and the antioxidant activities of selected SeNPs were evaluated by DPPH and FRAP assays. FT-IR analysis showed the production of SeNPs. The 12 h dark/12 h light cycles and continuous light exposure at pH 5 led to the production of stable SeNPs with sizes of 145 ± 6 and 171 ± 13 nm, respectively. Antioxidant activity of selected SeNPs was higher than sodium selenite. It seems that green synthesis is a safe method to produce SeNPs as well as a convenient method to scale-up this production.

Synthesis, characterization and investigation of algal oxidative effects of water-soluble copper phthalocyanine containing sulfonate groups.

In this study, the chemical and algicidal properties of the newly synthesized compound (2) were evaluated and its algal oxidative effects were determined in Arthrospira platensis and Chlorella vulgaris. First, we have reported on the synthesis and characterization of highly water-soluble copper (II) phthalocyanine (2), containing sodium 2-mercaptoethanesulfonate (2) substituents at the peripheral positions. Some spectroscopic techniques were used to characterize the new synthesized compound (2). In terms of biological properties, C. vulgaris were more tolerance to compound (2) than A. platensis depending to growth parameters. When SOD (Superoxide dismutase) activity significantly increased at 0.25 ppb and 1.5 ppb concentrations in A. platensis cultures, it increased at 6 ppb concentration in C. vulgaris cultures. GR (Glutathione reductase) activity decreased at 1 ppb and 1.5 ppb concentrations while APX (Ascorbate peroxidase) activity did not show a significant change at any concentrations in A. platensis cultures. GR activity showed a significant increase at 6 ppb concentration, while APX activity increased at all concentrations compared to control in C. vulgaris cultures. MDA (malondialdehyde) and H2O2 content decreased at 1 and 1.5 ppb concentrations but there were significant increases in the proline content at all concentrations compared to the control in A. platensis. MDA, H2O2 and free proline contents showed a significant increase at 0.5 ppb concentration in C. vulgaris. In conclusion, compound (2) have algicidal effects, and also it causes to oxidative stress in these organisms.

Differential response of photosynthetic apparatus towards alkaline pH treatment in NIES-39 and PCC 7345 strains of Arthrospira platensis.

Alkaline stress is one of the severe abiotic stresses, which is not well studied so far, especially among cyanobacteria. To affirm the characteristics of alkaline stress and the subsequent adaptive responses in Arthrospira platensis NIES-39 and Arthrospira platensis PCC 7345, photosynthetic pigments, spectral properties of thylakoids, PSII and PSI activities, and pigment-protein profiles of thylakoids under different pH regimes were examined. The accessory pigments showed a pH-mediated sensitivity. The pigment-protein complexes of thylakoids are also affected, resulting in the altered fluorescence emission profile. At pH 11, a possible shift of the PBsome antenna complex from PSII to PSI is observed. PSII reaction center is found to be more susceptible to alkaline stress in comparison to the PSI. In Arthrospira platensis NIES-39 at pH 11, a drop of 68% in the oxygen evolution with a significant increase of PSI activity by 114% is recorded within 24 h of pH treatment. Alterations in the cellular ultrastructure of Arthrospira platensis NIES-39 at pH 11 were observed, along with the increased number of plastoglobules attached with the thylakoid membranes. Arthrospira platensis NIES-39 is more adaptable to pH variation than Arthrospira platensis PCC 7345.

Acute toxicity of textile dye Methylene blue on growth and metabolism of selected freshwater microalgae.

Microalgae are ecologically important species in aquatic ecosystems due to their role as primary producers. The inhibition of growth of microalgae due to dye pollution results in an upheaval in the trophic transfer of nutrients and energy in aquatic ecosystems. Therefore, this investigation aimed to evaluate the toxicity of a textile dye Methylene blue (MB) on two microalgae viz. Chlorella vulgaris and Spirulina platensis. An exposure of the unialgal populations of both the microalgae towards graded concentrations of the dye showed a concentration-dependent decrease in specific growth rate, pigment and protein content. In the toxicity study of 24 -96-h, following the OECD guidelines 201, the EC50 values of C. vulgaris and S. platensis ranged from 61.81 to 5.43 mg/L and 5.83 to 1.08 mg/L respectively revealing that S. platensis exhibited a higher level of susceptibility towards the dye as compared to C. vulgaris and the latter is more tolerant to the dye toxicity even at higher concentrations. The findings indicate that the response to dye is a species-specific phenomenon. Given the differences in the cell structure and enzymatic pathways in Spirulina platensis (a prokaryote) and Chlorella vulgaris (an eukaryote), the tolerance levels can differ. After 96-h exposure of C. vulgaris to MB (100 mg/L), the chlorophyll-a, b and carotenoid content were reduced 2.5, 5.96 and 3.57 times in comparison to control whereas in S. platensis exposure to MB (10 mg/L), the chlorophyll-a and carotenoid content were reduced 3.59 and 5.08 times in comparison to control. After 96-h exposure of C. vulgaris and S. platensis to the dye (20 mg/L), the protein content was found to be 4.34 and 2.75 times lower than the control. The protein content has decreased in accordance with the increase in dye concentration.

Optimization of production and intrinsic viscosity of an exopolysaccharide from a high yielding Virgibacillus salarius BM02: Study of its potential antioxidant, emulsifying properties and application in the mixotrophic cultivation of Spirulina platensis.

Virgibacillus salarius BM02 was identified as a highly exopolysaccharide (EPS) producing bacterium. The EPS production and its physico-chemical properties (intrinsic viscosity and total sugars/protein (TS/P) ratio) were optimized using Box-Behnken experimental design. Maximum EPS production of 5.87 g L-1 with TS/P ratio of 12.56 and intrinsic viscosity of 0.13 dL g-1 was obtained at optimal conditions of sucrose (4.0% w/v), peptone (0.75% w/v) and incubation period of 4.69 day. The monosaccharide composition of EPS was mannose, arabinose and glucose at a molar ratio of 1.0:0.26:0.08. The EPS showed high water solubility (38.5%), water holding capacity (514.46%) and foaming capacity (55.55%). The EPS showed moderate antioxidant activity in vitro and good emulsion stabilizing properties against several hydrophobic compounds. The emulsifying activity was stable at different temperatures, pH and ionic strength. Additionally, the acid hydrolysate of the EPS was evaluated as a carbon source for the mixotrophic cultivation of industrially important Spirulina platensis. It induced an enhancement of not only biomass production of S. platensis, but also cellular contents (pigments, proteins and lipids) leading to higher nutritional value.

Optimization Growth of Spirulina (Arthrospira) Platensis in Photobioreactor Under Varied Nitrogen Concentration for Maximized Biomass, Carotenoids and Lipid Contents.

AIMS AND BACKGROUND: Spirulina (Arthrospira) platensis (SP) microalgae were cultured in Zarrouk Medium (ZM), containing three nitrogen concentrations (N-limited, N-optimal and Nrich medium) in ten liter-photo-bioreactor (10 L PBR) for 15-days, in order to study changes in lipid compounds (total carotenoids and total lipids and their effect on fatty acid profile). Based on US patent, the yield of bioactive compounds (such as gamma-linolenic acid GLA, C18:3) extracted from microalgae biomass, mainly depends on the extraction processes (1). GLA has much attention with respect to its therapeutic properties such as its ability to decrease blood cholesterol levels. METHODS: The impact of the addition of N in cultures of S. platensis in terms of growth, biomasses and induced lipid compounds (total carotenoids and total lipid contents and its fatty acid profile), as well as the Sonication (SON) and Microwave (MIC) process as aiding techniques for lipid extraction compared with a Cold Condition (COL), was examined. GC/MS method was used to determine the fatty acid profile of lipid extract of SP cultures. RESULTS: In all S. platensis tested culture, the SP was growing successfully, with varying degrees. In N-rich media, the highest cell growth rate and biomass yield were obtained compared with that recorded in other cultures. Under an N-limited condition, SP had higher Total Carotenoids (TCAR, 45.54 mg/g dw) and total lipid contents (TL, 29.51%± 1.92 g/100g dw) compared with that recorded either in N-rich (11.2 mg/g dw) or in N-optimal (6.23 mg/g dw) cultures. Thus, SP copes with the N -stress by altering the metabolic pathways towards inducing lipid biosynthesis. To maximize the TL and TCAR extraction yields, from N-limited cultures, a set of operating process was applied including the Sonication (SON) and Microwave (MIC), which were used as aiding techniques for lipid extraction compared with the Cold Condition (COL) techniques. The results showed that the extraction efficiency of the S. platensis TL increased in the following order: MIC (29.51%± 1.92) > SON (25.46% ± 1.65> COL (20.43% ±1.43). In a comparative study for its fatty acid profiles (FAPs) among all SP cultures, lipids were analyzed by GC/MS. The predominant fatty acids (>10%, of total FA) were found to be myristic acid (C14:0, MA), palmitic acid (C16:0, PA) and oleic acid (C18:1). CONCLUSION: The study concluded that the N-limited condition was found to have a strong influence on biomass dry weight and lipid contents and total carotenoids in SP cells compared to either Nrich or N-optimal conditions. The use of sonication and the microwave techniques lead to a great increase in the extraction of lipid contents and in high amount Polyunsaturated Fatty Acids (PUFAs) in N-limited cultures, in particular, the omega-6 (ω 6) and omega-3 (ω 3) of the essential C18 fatty acids. It seems that the SP rich in lipid content with a high amount of GLC produced under nitrogen limitation in PBR conditions can be used as a food additive or as a nutritional supplement.

Mixotrophic cultivation of Spirulina platensis in dairy wastewater: Effects on the production of biomass, biochemical composition and antioxidant capacity.

Mixotrophic cultivation of microalgae provides a very promising alternative for producing carbohydrate-rich biomass to convert into bioethanol and value-added biocompounds, such as vitamins, pigments, proteins, lipids and antioxidant compounds. Spirulina platensis may present high yields of biomass and carbohydrates when it is grown under mixotrophic conditions using cheese whey. However, there are no previous studies evaluating the influence of this culture system on the profile of fatty acids or antioxidant compounds of this species, which are extremely important for food and pharmaceutical applications and would add value to the cultivation process. S. platensis presented higher specific growth rates, biomass productivity and carbohydrate content under mixotrophic conditions; however, the antioxidant capacity and the protein and lipid content were lower than that of the autotrophic culture. The maximum biomass yield was 2.98 ±0.07 g/L in growth medium with 5.0% whey. The phenolic compound concentration was the same for the biomass obtained under autotrophic and mixotrophic conditions with 2.5% and 5.0% whey. The phenolic compound concentrations showed no significant differences except for that in the growth medium with 10.0% whey, which presented an average value of 22.37±0.14 mg gallic acid/g. Mixotrophic cultivation of S. platensis using whey can be considered a viable alternative to reduce the costs of producing S. platensis biomass and carbohydrates, shorten cultivation time and produce carbohydrates, as it does not require adding expensive chemical nutrients to the growth medium and also takes advantage of cheese whey, an adverse dairy industry byproduct.

The toxicological effects of oxybenzone, an active ingredient in suncream personal care products, on prokaryotic alga Arthrospira sp. and eukaryotic alga Chlorella sp.

Oxybenzone (OBZ; benzophenone-3, CAS# 131-57-7) is a known pollutant of aquatic and marine ecosystems, and is an ingredient in over 3000 personal care products, as well as many types of plastics. The aim of this study is to explore the different toxicities of OBZ on an eukaryotic (Chlorella sp.) and a prokaryotic algae (Arthrospira sp.). OBZ is a photo-toxicant, with all observed toxicities more sever in the light than in the dark. Cell growth and chlorophyll inhibition were positively correlated with increasing OBZ concentrations over time. Twenty days treatment with OBZ, as low as 22.8 ng L-1, significantly inhibited the growth and chlorophyll synthesis of both algae. Both algae were noticeably photo-bleached after 7 days of exposure to OBZ concentrations higher than 2.28 mg L-1. Relatively low OBZ concentrations (0.228 mg L-1) statistically constrained photosynthetic and respiratory rates via directly inhibiting photosynthetic electron transport (PET) and respiration electron transport (RET) mechanisms, resulting in over production of reactive oxygen species (ROS). Transmission and scanning electron microscopy showed that the photosynthetic and respiratory membrane structures were damaged by OBZ exposure in both algae. Additionally, PET inhibition suppressed ATP production for CO2 assimilation via the Calvin-Benson cycle, further limiting synthesis of other biomacromolecules. RET restriction limited ATP generation, restricting the energy supply used for various life activities in the cell. These processes further impacted on photosynthesis, respiration and algal growth, representing secondary OBZ-induced algal damages. The data contained herein, as well as other studies, supports the argument that global pelagic and aquatic phytoplankton could be negatively influenced by OBZ pollution.

Low pH rather than high CO2 concentration itself inhibits growth of Arthrospira.

Microalga is a promising candidate for bio-mitigation of CO2. It has been longtime recognized that high CO2 concentration would impose stresses on microalga to suppress the growth. However, this concept was challenged in this research by investigating the growth, photosynthesis and anti-oxidant characteristics of Arthrospira platensis under independent effects of CO2 concentrations and pH. Results showed the growth of A. platensis was only inhibited when broth was in acidic pH. Microalgal cells could deal with high CO2 concentration readily if medium pH was maintained in favorite level. Photosynthesis was inhibited swiftly and significantly under acidified condition. The singlet oxygen was produced in low level for alkalic pH treatment, however it burst quickly after low pH stress was imposed. Accordingly, it was proposed that the phenomena of high CO2 intolerance was caused by CO2 induced pH decline rather than high CO2 concentration itself. This finding has significance on large scale application of microalga based CO2 mitigation and flue gas treatment since it proved concentrated CO2 could be directly assimilated without dilution.

Impact of CO2 concentration and ambient conditions on microalgal growth and nutrient removal from wastewater by a photobioreactor.

The increase in atmospheric CO2 concentration and the release of nutrients from wastewater treatment plants (WWTPs) are environmental issues linked to several impacts on ecosystems. Numerous technologies have been employed to resolves these issues, nonetheless, the cost and sustainability are still a concern. Recently, the use of microalgae appears as a cost-effective and sustainable solution because they can effectively uptake CO2 and nutrients resulting in biomass production that can be processed into valuable products. In this study single (Spirulina platensis (SP.PL) and mixed indigenous microalgae (MIMA) strains were employed, over a 20-month period, for simultaneous removal of CO2 from flue gases and nutrient from wastewater under ambient conditions of solar irradiation and temperature. The study was performed at a pilot scale photo-bioreactor and the effect of feed CO2 gas concentration in the range (2.5-20%) on microalgae growth and biomass production, carbon dioxide bio-fixation rate, and the removal of nutrients and organic matters from wastewater was assessed. The MIMA culture performed significantly better than the monoculture, especially with respect to growth and CO2 bio-fixation, during the mild season; against this, the performance was comparable during the hot season. Optimum performance was observed at 10% CO2 feed gas concentration, though MIMA was more temperature and CO2 concentration sensitive. MIMA also provided greater removal of COD and nutrients (~83% and >99%) than SP.PL under all conditions studied. The high biomass productivities and carbon bio-fixation rates (0.796-0.950 gdw·L-1·d-1 and 0.542-1.075 gC·L-1·d-1 contribute to the economic sustainability of microalgae as CO2 removal process. Consideration of operational energy revealed that there is a significant energy benefit from cooling to sustain the highest productivities on the basis of operating energy alone, particularly if the indigenous culture is used.

The in vitro synergistic denaturation effect of heat and surfactant on photosystem I isolated from Arthrospira Platensis.

Photosystem I (PSI) generates the most negative redox potential found in nature, and the performance of solar energy conversion into alternative energy sources in artificial systems highly depends on the thermal stability of PSI. Thus, understanding thermal denaturation is an important prerequisite for the use of PSI at elevated temperatures. To assess the thermal stability of surfactant-solubilized PSI from cyanobacteria Arthrospira Platensis, the synergistic denaturation effect of heat and surfactant was studied. At room temperature, surfactant n-dodecyl-ß-D-maltoside solubilized PSI trimer gradually disassembles into PSI monomers and free pigments over long time. In the solubilizing process of PSI particles, surfactant can uncouple pigments of PSI, and the high concentration of surfactant causes the pigment to uncouple more; after the surfactant-solubilizing process, the uncoupling is relatively slow. During the heating process, changes were monitored by transmittance T800nm, ellipticity θ686nm and θ222nm, upon slow heating (1.5 °C per minute) of samples in Tris buffer (20 mM, pH 7.8) from 20 to 95 °C. The thermal denaturation of surfactant-solubilized PSI is a much more complicated process, which includes the uncoupling of pigments by surfactants, the disappearance of surrounding surfactants, and the unfolding of PSI α-helices. During the heating process, the uncoupling chlorophyll a (Chla) and converted pheophytin (Pheo) can form excitons of Chla-Pheo. The secondary structure α-helix of PSI proteins is stable up to 87-92 °C in the low-concentration surfactant solubilized PSI, and high-concentration surfactant and pigments uncoupling can accelerate the α-helical unfolding.

Effect of ammonium nitrogen on microalgal growth, biochemical composition and photosynthetic performance in mixotrophic cultivation.

To enhance microalgal growth and optimize ammonium utilization, the effect of ammonium on microalgal growth, biochemical composition and photosynthetic performance were investigated by mixotrophic cultivation of microalga Spirulina platensis comparing with autotrophic cultivation. The results indicated that elevated ammonium significantly affected the microalgal growth, but the microalga in mixotrophic cultivation showed better growth and stronger tolerance to higher ammonium. The microalgal proteins were increased by increasing nitrogen concentration. The synthesis of microalgal carbohydrates was inhibited by higher ammonium, especially in mixotrophic cultivation. The addition of ammonium decreased the microalgal lipids in autotrophic cultivation but increased microalgal lipids in mixotrophic cultivation. Ammonium negatively affected the microalgal photosynthetic performance. The inhibition was intensified by elevated ammonium, inducing stronger photosystem protection mechanism, particularly in mixotrophic cultivation. The rate of ammonium inhibition to the microalgal photosystem was quick in the early stage by decreasing electron transport rate of PS II.

Enhancement of the carbohydrate content in Spirulina by applying CO2, thermoelectric fly ashes and reduced nitrogen supply.

This study focused on evaluating whether the injection of CO2, which is associated with the use of thermoelectric fly ashes and a reduced supply of nitrogen, affects the production of intracellular carbohydrates from Spirulina. For this purpose, the addition of 0.25 g L-1 of NaNO3, along with a 10% (v v-1) of CO2 injection, a flow rate of 0.3 vvm for 1 or 5 min, as well as 0, 120 and 160 ppm of fly ashes, was studied. The assays with 120 ppm of fly ashes presented the best kinetic parameters and CO2 biofixation rate, regardless of the CO2 injection time. Meanwhile, the experiments with 120 and 160 ppm of fly ash and CO2 injection for 1 min presented 63.3 and 61.0% (w w-1) of carbohydrates, respectively. Thus, this study represents an important strategy to increase the accumulation of carbohydrates in Spirulina, with potential application in the production of bioethanol.

Neuroprotective Activities of Spirulina platensis in the 6-OHDA Model of Parkinson's Disease Are Related to Its Anti-Inflammatory Effects.

Spirulina platensis (SPI) is a cyanobacterium, presenting anti-inflammatory and antioxidant actions. Considering the importance of inflammation and oxidative stress in Parkinson's disease (PD), SPI neuroprotective effects were evaluated in a model of PD. Male Wistar rats were divided into: sham-operated (SO), untreated 6-OHDA and 6-OHDA treated with SPI (25 and 50 mg/kg, p.o.). The 6-OHDA was injected into the right striata and SPI treatments started 24 h later for 2 weeks. The SO and untreated 6-OHDA-lesioned groups were administered with distilled water, for the same period. Afterwards, the animals were subjected to the apomorphine-induced rotational test and euthanized for striatal measurements of DA and DOPAC, nitrite and TBARS and immunohistochemistry assays for TH, DAT, iNOS and COX-2. SPI reduced the apomorphine-induced rotational behavior, DA and DOPAC depletions and nitrite and TBARS increases, at its high dose. Furthermore, TH and DAT immunoreactivities in the lesioned striatum of the untreated 6-OHDA-lesioned group were attenuated by SPI. Similarly, immunoreactivities for iNOS and COX-2 were also decreased after SPI treatments. In conclusion, we showed that behavioral and neurochemical alterations in hemiparkinsonian rats were partly reversed by SPI, characterizing the neuroprotective potential of Spirulina and stimulating translational studies focusing on its use as an alternative treatment for PD.

Overcoming Intrinsic Restriction Enzyme Barriers Enhances Transformation Efficiency in Arthrospira platensis C1.

The development of a reliable genetic transformation system for Arthrospira platensis has been a long-term goal, mainly for those trying either to improve its performance in large-scale cultivation systems or to enhance its value as food and feed additives. However, so far, most of the attempts to develop such a transformation system have had limited success. In this study, an efficient and stable transformation system for A. platensis C1 was successfully developed. Based on electroporation and transposon techniques, exogenous DNA could be transferred to and stably maintained in the A. platensis C1 genome. Most strains of Arthrospira possess strong restriction barriers, hampering the development of a gene transfer system for this group of cyanobacteria. By using a type I restriction inhibitor and liposomes to protect the DNA from nuclease digestion, the transformation efficiency was significantly improved. The transformants were able to grow on a selective medium for more than eight passages, and the transformed DNA could be detected from the stable transformants. We propose that the intrinsic endonuclease enzymes, particularly the type I restriction enzyme, in A. platensis C1 play an important role in the transformation efficiency of this industrial important cyanobacterium.