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.

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.

Synergistic effects of Spirulina platensis cultivation in textile wastewater towards nutrient removal and seed germination study.

Recent escalating concerns surrounding textile wastewater pollution and the urgent need for sustainable treatment solutions to mitigate its environmental impact. This study investigates the multifaceted effects of Spirulina platensis (SP) cultivation in textile wastewater from two different sources (TWW1 and TWW2), focusing on growth kinetics, Chemical Oxygen Demand (COD), and nutrient removal percentage, and seed germination enhancement. Results showed that SP exhibited comparable growth performance in TWW1 and TWW2 to the control, indicating its potential for sustainable wastewater treatment. Moreover, maximum COD removal percentages were achieved, reaching 62.59 ± 1.88 % for TWW1 and 46.68 ± 1.40 % for TWW2 on day 5. The COD removal process aligns best with the first-order kinetic model. Nutrient removal rates showed decreasing trends over time, with maximum phosphate removal percentages of 36.42 ± 0.73 % for TWW1 and 62.18 ± 1.24 % for TWW2, and maximum ammonia removal percentages of 59.34 ± 1.18 % for TWW1 and 69.31 ± 1.39 % for TWW2. FTIR analysis confirmed pollutant removal-induced changes in algal biomass functional groups. Seed germination studies indicated enhanced shoot and root development of vigna radiatas using treated TWW1 and TWW2 compared to the control, suggesting potential applications for irrigation. An increase in the lipid & carbohydrate content post-treatment was observed and it would be suitable for biofuel production. This comprehensive assessment demonstrates the synergistic benefits of phycoremediation in simultaneously removing pollutants, promoting plant growth, and enhancing wastewater treatment efficiency, underscoring its potential for sustainable water management practices.

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.

Comparative Analysis of Effect of Culture Conditions on Growth and C-Phycocyanin Production in Helical and Linear Spirulina.

Spirulina (Arthrospira and Spirulina spp.) has always been characterized by the helical trichomes, despite the existence of linear forms. A great debate is now open on the morphological flexibility of Spirulina, but it seems that both trichome morphology and C-phycocyanin (C-PC) concentrations are influenced by the culture conditions.This work compared the effect of some key growth factors (medium pH as well as its carbon, potassium, and salt contents) on the growth and C-PC concentration of helical and linear Spirulina strains. Further, two-phase strategies, including light and nitrogen variation, were applied to increase the in vivo C-PC accumulation into the trichomes. Results showed that high pH induced trichomes elongation and improved growth but decreased C-PC content (+ 65 and + 43% vs. -83 and -49%, for helical and linear strains, respectively). Variations in carbon and salt concentrations negatively impacted growth and C-PC content, even if the linear strain was more robust against these fluctuations. It was also interesting to see that potassium increasing improved growth and C-PC content for both strains.The variation of light wavelength during the enrichment phase (in the two-phase strategy) improved by 50% C-PC accumulation in trichomes, especially after blue lighting for 96 h. Similar result was obtained after 48 h of nitrogen reduction, while its removal from the medium caused trichomes disintegration. The current work highlights the robustness of linear Spirulina strain and presents an efficient and scalable way to increase C-PC in vivo without affecting growth.

Microalgae production in olive mill wastewater fractions and cattle digestate slurry: Bioremediation effects and suitability for energy and feed uses.

The possibility of obtaining energy or nutritive streams and bioremediation as an add-on opens new perspectives for the massive culturing of microalgal biomass on waste waters generated by the agro-food sector. Ordinary revenue streams are fully preserved, or even boosted, if they are used in microalgal cultivation; however, the suitability of wastewaters depends on multiple nutritional and toxic factors. Here, the effect of modulating the Olive Mill Wastewater (OMW) and cattle digestate (CD) fraction in the formulation of a growth medium on biomass accumulation and productivity of selected biomass fractions and their relevance for biofuel and/or feed production were tested for the microalga Scenedesmus dimorphus and for the cyanobacterium Arthrospira platensis (Spirulina). Tests highlighted the strong S. dimorphus adaptability to digestate, as on OMW, compared to A. platensis, with the maximum lipid storage (48 %) when culture medium was composed by 50 % of cattle digestate.

Cradle-to-gate life cycle assessment of Spirulina bioplastic produced via plasticization with glycerol.

Bioplastics have been used as alternatives to conventional petroleum-based plastics to lessen the burdens on marine and terrestrial environments due to their non-biodegradability and toxicity. However, recent studies have shown that not all bioplastics may be environmentally friendly. Microalgae, such as Spirulina that do not require arable land, have been identified as a potential bioplastic source. In this study, cradle-to-gate life cycle assessment (LCA) was carried out in openLCA program using the Agribalyse database, to evaluate the environmental impacts of Spirulina bioplastic, formed from plasticization of Spirulina powder with glycerol. Two processes were created for the inventories of (i) Spirulina powder and (ii) Spirulina bioplastic, where the output of the former served as an input for the latter. The extruded bioplastic sheets were food-grade and could be used as edible packaging materials. The bioplastic was also compared to conventional plastics and it was found that the energy consumption was 3.83 ± 0.26 MJ/kg-bioplastic, which was 12% and 22% higher than that of LDPE and PVC plastic films, respectively. The impacts on the environment showed that the chemical growth medium (Zarrouk medium) and electricity were the main contributors in most of the categories. Compared to the PVC and LDPE films, the Spirulina bioplastic's impacts on the aquatic ecosystems were 2-3 times higher. The global warming potential of the Spirulina bioplastic was 1.99 ± 0.014 kg CO2 eq, which was 23% and 47% lower than that of LDPE and PVC films, respectively. Sensitivity analysis was carried out by changing the electricity source and using alternative growth media. Except for the case of switching to solar energy, the results for other cases did not differ significantly from the base case scenario. Future studies were suggested to identify different greener alternatives to the growth medium as well as different energy mixes for more environmentally benign solutions.

Screening of biological properties of MoV2O2S2- and MoV2O4-based coordination complexes: Investigation of antibacterial, antifungal, antioxidative and antitumoral activities versus growing of Spirulina platensis biomass.

This paper deals with the biological potential of coordination compounds based on binuclear core [MoV2O2E2]2+ (E = O or S) coordinated with commercially available ligands such as oxalates (Ox2-), L-cysteine (L-cys2-), L-histidine (L-his-), Iminodiacetate (IDA2-), Nitrilotriacetate (HNTA2- or NTA3-) or ethylenediamine tetraacetate (EDTA4-) by means of various in vitro assays in a screening approach. Results suggest that the obtained complexes show weak antibacterial and antifungal properties while not being cytotoxic on cancerous and mammalian cells. In contrast, [Mo2O2E2(L-cys)2]2- complexes stand out as powerful antioxidant, whereas [Mo2O2E2(EDTA)]2- associating tetraphenylphosphonium counter-cations display strong antibiotic activity. Finally, some complexes have evidenced a positive activity towards the growing of spirulina platensis together with a modification of the proportions of biological components inside the cells. These findings reveal promising bioactivity of the bridged binuclear Mo(+V) cores inside complexes and encourage further research for new highly active yet non-toxic molecules for biological and biomedical applications.

Evaluation of strategies to enhance ammoniacal nitrogen tolerance by cyanobacteria.

In anaerobic digestion of agro-industrial effluents and livestock wastes, concentrations of ammoniacal nitrogen above 800 mg L-1 are reported to lead to the eutrophication of water bodies. Through the metabolic versatility of microalgae, this nitrogen source can be used and removed, producing carotenoids, phycobiliproteins, polyhydroxyalkanoates, and fatty acids of industrial interest. The challenge of making it feasible is the toxicity of ammoniacal nitrogen to microalgae. Therefore, three strategies were evaluated. The first one was to find species of cyanobacteria with high ammoniacal nitrogen removal efficiency comparing Arthrospira platensis, Synechocystis D202, and Spirulina labyrinthiformis cultivations. The most promising species was cultivated in the second strategy, where cell acclimatization and increasing of the inoculum were evaluated. The cultivation condition that culminated in the best efficiency of ammoniacal nitrogen removal was combined with the third strategy, which consisted of conducting the fed-batch bioprocess. In the batch mode, ammoniacal nitrogen was supplied only once in one fed and was present in high initial concentrations. In fed-batch, multiple feedings with low concentrations of ammoniacal nitrogen were used to decrease the inhibitory effect of ammoniacal nitrogen. Arthrospira platensis showed high potential for ammoniacal nitrogen removal. Using the highest initial cell concentration of Arthrospira platensis cultivated by fed-batch, an increase in the consumption of NH3 to 165.1 ± 1.8 mg L-1 and an ammoniacal nitrogen removal efficiency close to 90% were observed. Under this condition, 180.52 ± 11.67 mg g-1 of phycocyanin was attained. Also, the fed-batch cultivations have the potential to reduce the biomass cost production by 33% in comparison to batch experiments.

Magnetic fields exhibit a positive impact on lipid and biomass yield during phototrophic cultivation of Spirulina sp.

This study aimed to investigate the effects of magnetic field (MF) application (1, 12 and 24 h day -1) to Spirulina sp. LEB 18 in different photosynthesis cycles (dark and/or light) during short (15 days) and long periods (50 days) of cultivation. MF application was performed via two sources: ferrite magnets and solenoids. At the end of cultivation, the biomass was characterized in terms of lipids, proteins, and carbohydrates. In the 15 day cultures, the highest maximum biomass concentrations (2.06 g L-1 and 1.83 g L-1) were observed when 30 mT was applied for 24 h day -1 or 12 h day -1 (on the light cycle), respectively. MF application throughout cultivation (24 h day -1) for more than 30 days is not recommended. In all conditions, there was an increase in the lipid concentration (from 14 to 45%). The protein profile suggested important changes in photosystems I and II due to MF application. Cell morphology was not altered by MF application. In conclusion, the effects on the metabolism of Spirulina sp. are directly related to the photosynthesis cycle and time period in which the MF was applied.

Gene transcription and antioxidants production in Arthrospira (Spirulina) platensis grown under temperature variation.

AIM: To investigate the transcription of selected antioxidants and relevant genes under varying temperature conditions, and to identify the optimum temperature for antioxidants production by Arthrospira platensis. METHODS AND RESULTS: The dry weight (DW), pigment production, antioxidants production and gene transcription were examined in A. platensis growing under three temperatures of 23, 30 and 37°C. The cyanobacterial DW was highest in the high temperatures (30 and 37°C), while the pigments, such as Chl a, carotenoids, C-phycocyanin and total phycobiliprotein contents, showed their maximum value at 30°C. The total soluble protein and carbohydrate contents were highest at 30°C. Lipid peroxidation, as a marker for thermal stress, was high at 23°C, while higher temperatures remarkably reduced lipid peroxidation levels. Antioxidants activity was increased by 1·5-fold at 30°C and temperature fluctuations induced the antioxidant enzyme activities. The transcriptional abundance of heat shock protein (HSP90), glutamate synthase (GOGAT), delta-9 desaturase (desC), iron-superoxide dismutase (FeSOD) and the large subunit of Rubisco (rbcL) genes was measured under the same temperatures. CONCLUSION: The optimal temperature for growth, biochemical constituents and antioxidants of A. platensis is 30°C while some antioxidant enzyme activity increased at lower and higher temperatures. SIGNIFICANCE AND IMPACT OF THE STUDY: The study showed the significance of temperature for growth, enzymatic and non-enzymatic antioxidants and gene expression in A. platensis. This contributes to the knowledge of culturing A. platensis to harvest specific antioxidants or as an antioxidant-rich food source.

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.

Extracellular neutral protease from Arthrospira platensis: Production, optimization and partial characterization.

Proteases are industrially important catalysts. They belong to a complex family of enzymes that perform highly focused proteolysis functions. Given their potential use, there has been renewed interest in the discovery of proteases with novel properties and a constant thrust to optimize the enzyme production. In the present study, a novel extracellular neutral protease produced from Arthrospira platensis was detected and characterized. Its proteolytic activity was strongly activated by ß-mercaptoethanol, 5,5-dithio-bis-(2-nitrobenzoic acid) and highly inhibited by Hg2+ and Zn2+ metal ions which support the fact that the studied protease belongs to the cysteine protease family. Using statistical modelling methodology, the logistic model has been selected to predict A. platensis growth-kinetic values. The optimal culture conditions for neutral protease production were found using Box-Behnken Design. The maximum experimental protease activities (159.79 U/mL) was achieved after 13 days of culture in an optimized Zarrouk medium containing 0.625 g/L NaCl, 0.625 g/L K2HPO4 and set on 9.5 initial pH. The extracellular protease of A. platensis can easily be used in the food industry for its important activity at neutral pH and its low production cost since it is a valuation of the residual culture medium after biomass recovery.

Spirulina-in Silico-Mutations and Their Comparative Analyses in the Metabolomics Scale by Using Proteome-Based Flux Balance Analysis.

This study used an in silico metabolic engineering strategy for modifying the metabolic capabilities of Spirulina under specific conditions as an approach to modifying culture conditions in order to generate the intended outputs. In metabolic models, the basic metabolic fluxes in steady-state metabolic networks have generally been controlled by stoichiometric reactions; however, this approach does not consider the regulatory mechanism of the proteins responsible for the metabolic reactions. The protein regulatory network plays a critical role in the response to stresses, including environmental stress, encountered by an organism. Thus, the integration of the response mechanism of Spirulina to growth temperature stresses was investigated via simulation of a proteome-based GSMM, in which the boundaries were established by using protein expression levels obtained from quantitative proteomic analysis. The proteome-based flux balance analysis (FBA) under an optimal growth temperature (35 °C), a low growth temperature (22 °C) and a high growth temperature (40 °C) showed biomass yields that closely fit the experimental data obtained in previous research. Moreover, the response mechanism was analyzed by the integration of the proteome and protein-protein interaction (PPI) network, and those data were used to support in silico knockout/overexpression of selected proteins involved in the PPI network. The Spirulina, wild-type, proteome fluxes under different growth temperatures and those of mutants were compared, and the proteins/enzymes catalyzing the different flux levels were mapped onto their designated pathways for biological interpretation.

Arthrospiribacter ruber gen. nov., sp. nov., a novel bacterium isolated from Arthrospira cultures.

Polyphasic analysis of ten isolates of the red-pigmented bacteria isolated from ten Arthrospira cultures originating from different parts of the world is described. The 16S rRNA analysis showed <95 % identity with the known bacteria on public databases, therefore, additional analyses of fatty acids profiles, MALDI-TOF/MS, genome sequencing of the chosen isolate and following phylogenomic analyses were performed. Gram-stain-negative, strictly aerobic rods were positive for catalase, negative for oxidase, proteolytic and urease activity. Major fatty acids were 15 : 0 iso, 17:0 iso 3 OH and 17:1 iso w9c/16:0 10-methyl. The whole phylogenomic analyses revealed that the genomic sequence of newly isolated strain DPMB0001 was most closely related to members of Cyclobacteriaceae family and clearly indicated distinctiveness of newly isolated bacteria. The average nucleotide identity and in silico DNA-DNA hybridisation values were calculated between representative of the novel strains DPMB0001 and its phylogenetically closest species, Indibacter alkaliphilus CCUG57479 (LW1)T (ANI 69.2 % is DDH 17.2 %) and Mariniradius saccharolyticus AK6T (ANI 80.02 % isDDH 26.1 %), and were significantly below the established cut-off <94 % (ANI) and <70 % (isDDH) for species and genus delineation. The obtained results showed that the analysed isolates represent novel genus and species, for which names Arthrospiribacter gen nov. and Arthrospiribacter ruber sp. nov. (type strain DPMB0001=LMG 31078=PCM 3008) is proposed.

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.

Extraction of phycocyanin-A natural blue colorant from dried spirulina biomass: Influence of processing parameters and extraction techniques.

Phycocyanin, a natural blue colorant, is typically extracted from liquid biomass of Arthrospira platensis, a blue-green algae called spirulina. In this study, we developed a scalable process to extract phycocyanin from dried spirulina biomass. First, we established the optimal ionic strength and pH for the extraction buffer. The results showed that a minimum ionic strength (>5 g/L NaCl) must be maintained to minimize the co-extraction of the green chlorophyll. The optimal pH of the phosphate buffer (100 mM) for phycocyanin extraction is 7.5; however, the pH should be immediately adjusted to 6.0 to 6.5 after the extraction to keep phycocyanin stable. Second, we also investigated three processing techniques, that is, high-pressure processing (HPP), pulsed electric field (PEF), and ultrasonication, to break the cell walls of spirulina and facilitate the release of phycocyanins into extraction buffers. HPP and PEF do not lead to the release of phycocyanin into the extraction buffer. However, ultrasonication breaks down the spirulina into fine particles and releases most of the phycocyanin, along with other impurities, immediately after the treatment. Last, it has been revealed that most of the phycocyanin can be extracted from biomass within 3 hr by phosphate buffer only (pH 7.5, 100 mM) at room temperature. It is concluded that there is no need to treat the rehydrated biomass solution by HPP, PEF, or ultrasonication due to the minimal benefits they brought for the extraction. Based on these results, we proposed an extraction process for the plant production of phycocyanin starting from dried spirulina biomass. PRACTICAL APPLICATIONS: Limited information can be found on the extraction of phycocyanin from dried spirulina biomass, especially how to better preserve the natural blue color of phycocyanin during extraction. We have investigated the method and presented a different view from previous processes. Pulsed electric field, high-pressure processing, and ultrasonication were employed to accelerate the extraction of phycocyanin from dried biomass. However, it was found that, unlike the extraction from live wet biomass, these techniques do not help with the extraction from dried biomass. Based on investigations, we have proposed a process that can be easily scaled up for the commercial production of phycocyanin from dried spirulina biomass.

Identification of a gene regulated by HetR, a master regulator of heterocyst differentiation, in the non-heterocyst-forming filamentous cyanobacterium Arthrospira platensis NIES-39.

Cyanobacteria are a morphologically and physiologically diverse group of bacteria, which contains unicellular and multicellular filamentous strains. Some filamentous cyanobacteria, such as Anabaena sp. strain PCC 7120, form a differentiated cell called a heterocyst. The heterocyst is a specialized cell for nitrogen fixation and is differentiated from a vegetative cell in response to depletion of combined nitrogen in the medium. In Anabaena PCC 7120, it has been demonstrated that hetR, which encodes a transcriptional regulator, is necessary and sufficient for heterocyst differentiation. However, comprehensive genomic analysis of cyanobacteria has shown that hetR is present in non-heterocyst-forming cyanobacteria. Almost all filamentous cyanobacteria have hetR, but unicellular cyanobacteria do not. In this study, we conducted genetic and biochemical analyses of hetR (NIES39_C03480) of the non-heterocyst-forming cyanobacterium Arthrospira platensis NIES-39. HetR of A. platensis was able to complement the hetR mutation in Anabena PCC 7120 and recognized the same DNA sequence as Anabaena HetR. A search of the A. platensis genome revealed the HetR-recognition sequence within the promoter region of NIES39_O04230, which encodes a protein of unknown function. Expression from the NIES39_O04230 promoter could be suppressed by HetR in Anabaena PCC 7120. These data support the conclusion that NIES39_O04230 is regulated by HetR in A. platensis NIES-39.

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.