Viromic and Metagenomic Analyses of Commercial Spirulina Fermentations Reveal Remarkable Microbial Diversity.

Commercially produced cyanobacteria preparations sold under the name spirulina are widely consumed, due to their traditional use as a nutrient-rich foodstuff and subsequent marketing as a superfood. Despite their popularity, the microbial composition of ponds used to cultivate these bacteria is understudied. A total of 19 pond samples were obtained from small-scale spirulina farms and subjected to metagenome and/or virome sequencing, and the results were analysed. A remarkable level of prokaryotic and viral diversity was found to be present in the ponds, with Limnospira sp. and Arthrospira sp. sometimes being notably scarce. A detailed breakdown of prokaryotic and viral components of 15 samples is presented. Twenty putative Limnospira sp.-infecting bacteriophage contigs were identified, though no correlation between the performance of these cultures and the presence of phages was found. The high diversity of these samples prevented the identification of clear trends in sample performance over time, between ponds or when comparing successful and failed fermentations.

Phylogenetic distribution and characterization of conserved C-di-GMP metabolizing proteins in filamentous cyanobacterium Arthrospira.

Cyclic diguanosine monophosphate (c-di-GMP) is a second messenger in bacteria that regulates multiple biological functions, including biofilm formation, virulence, and intercellular communication. However, c-di-GMP signaling is virtually unknown in economically important filamentous cyanobacteria, Arthrospira. In this study, we predicted 31 genes encoding GGDEF-domain proteins from A. platensis NIES39 as potential diguanylate cyclases (DGCs). Phylogenetic distribution analysis showed five genes (RS09460, RS04865, RS26155, M01840, and E02220) with highly conserved distribution across 25 Arthrospira strains. Adc1 encoded by RS09460 was further characterized as a typical DGC. By establishing the genetic transformation system of Arthrospira, we demonstrated that the overexpression of Adc1 promoted the production of extracellular polymeric substances (EPS), which in turn caused the aggregation of filaments. We also confirmed that RS04865 and RS26155 may encode active DGCs, while enzymatic activity assays showed that proteins encoded by M01840 and E02220 have phosphodiesterase (PDE) activity. Meta-analysis revealed that the expression profiles of RS09460 and RS04865 were unaffected under 31 conditions, suggesting that they may function as conserved genes in maintaining the basal level of c-di-GMP in Arthrospira. In summary, this report will provide the basis for further studies of c-di-GMP signal in Arthrospira.

Protocol for the transformation and engineering of edible algae Arthrospira platensis to generate heterologous protein-expressing strains.

Here, we present a protocol for harnessing the natural transformability of the edible algae Arthrospira platensis (common name: spirulina) to generate strains that express heterologous proteins. We describe the preparation of plasmids and the steps to grow A. platensis. We then detail the transformation and passage of the strains, followed by genomic DNA extraction and genotyping to assess integration of the gene of interest. This simple transformation protocol can be applied to genome manipulation of edible algae. For complete details on the use and execution of this protocol, please refer to Jester et al. (2022).1.

Study on the Bioconversion of Curcumin to Calebin-A Using Spirulina subsalsa and Its Taxonomic Resolution Using 16S rRNA Analysis.

Due to morphological convergence and the application of numerous taxonomic concepts, the systematics of filamentous cyanobacteria is still a significant problem. The incorporation and integration of modern molecular, cyto-morphological and ecological approaches in cyanobacterial taxonomy are essential and must be acknowledged as the valid methods for the development of their modern systematics. In this study, method of using 16S rRNA gene sequences to infer the genetic relationships of twelve freshwater cyanobacterial isolates amongst themselves was evaluated. The taxonomic resolution was inferred from their phylogenetic tree, in silico restriction digestion analysis and secondary structure prediction. These methods allowed cyanobacterial genera to be well distinguished with their genotypic and phenotypic differences. Amongst twelve strains, Spirulina subsalsa with highest protein content was used in this study for evaluating the stability of Curcumin which is a curcuminoid compound reported from Curcuma longa. Though they have wide properties, they still lack stability and bioavailability. It is reported previously that microbes are used for biotransformation and act as a carrier molecule. Therefore, in this study, Spirulina incorporated with curcumin resulted with pH stability of curcumin and were found to have a biotransformation into Calebin-A, curcuminoid compound originally present in smaller amount (0.005%) in C. longa with various biomedical applications.

Analysis of morphological change mechanism of linear Arthrospira platensis based on transcriptome results.

Arthrospira platensis is a kind of filament cyanobacteria, which is mainly helical with a few linear. The shape of the filaments, such as the length and the pitch, may change with the changes in the environment. Natural Arthrospira platensis FACHB793 is linear, although it has become helical due to a mutation introduced in the process of cultivation. To study the molecular mechanism responsible for the morphological changes of the filaments, two samples were isolated from a natural mutant of Arthrospira platensis FACHB793, which were helical shaped (named A793_H) and linear shaped (named A793_L). Transcriptome sequencing, GO and KEGG enrichment analysis showed that the expression of genes related to or involved in peptidoglycan biosynthesis, beta lactam resistance, photosynthetic antenna protein expression, bacterial secretion, and ABC transporter activity changed between the two samples. The expression of murE and murG in the peptidoglycan biosynthesis pathway and that of oppD in beta lactam resistance were all down-regulated in the helical filaments, which may be related to the longer cell wall and higher peptidoglycan synthesis in linear filaments than helical filaments. In helical filaments, the up-regulation of tatC gene expression in bacterial secretion may be related to the secretion of peptidoglycan degrading enzymes, which may help to change the shape from linear to helical. Moreover, apcA and cpcA in photosynthetic antenna protein expression and nrt and nirA in nitrogen metabolism were all down regulated in the helical filaments, which may be due to the deformed shape of A. platensis FACHB793, resulting in decreased photosynthetic activity in helical filaments. This research provides a foundation for elucidating the possible morphogenetic mechanism of Arthrospira platensis.

Development of spirulina for the manufacture and oral delivery of protein therapeutics.

The use of the edible photosynthetic cyanobacterium Arthrospira platensis (spirulina) as a biomanufacturing platform has been limited by a lack of genetic tools. Here we report genetic engineering methods for stable, high-level expression of bioactive proteins in spirulina, including large-scale, indoor cultivation and downstream processing methods. Following targeted integration of exogenous genes into the spirulina chromosome (chr), encoded protein biopharmaceuticals can represent as much as 15% of total biomass, require no purification before oral delivery and are stable without refrigeration and protected during gastric transit when encapsulated within dry spirulina. Oral delivery of a spirulina-expressed antibody targeting campylobacter-a major cause of infant mortality in the developing world-prevents disease in mice, and a phase 1 clinical trial demonstrated safety for human administration. Spirulina provides an advantageous system for the manufacture of orally delivered therapeutic proteins by combining the safety of a food-based production host with the accessible genetic manipulation and high productivity of microbial platforms.

Effect of Spirulina and Ferrous Fumarate on Intestinal Morphology and the Diversity of Gut Microbiota of Yellow River Carp.

The study aimed to investigate the effect of diets supplemented with Spirulina and the mixture of Spirulina and ferrous fumarate on intestinal morphology and the diversity of gut microbiota of Yellow River carp. The results showed that the Spirulina and the mixture of Spirulina and ferrous fumarate could promote the development of intestinal villi, increase the thickness of intestinal muscular layer. Additionally, high-throughput sequencing of 16S rRNA gene revealed that the Spirulina and the mixture of Spirulina and ferrous fumarate could alter the composition, diversity, and richness of intestinal microbial communities. The relative abundances of the predominant phyla Firmicutes and Verrucomicrobia showed significant changes at the phylum level after fed with Spirulina and ferrous fumarate. At the genus level, the predominant genera with marked differences in abundances were Flavobacterium, Aeromonas, and Brevinema. In conclusion, this study indicated the Spirulina and the ferrous fumarate could alter the intestinal microbiota structure and could also cause positive impacts on the health of Yellow River carp. This study provides the valuable information for elucidating the mechanisms of Spirulina and ferrous fumarate in aquatic animals in the future.

Comparative Genomics and Physiological Investigation of a New Arthrospira/Limnospira Strain O9.13F Isolated from an Alkaline, Winter Freezing, Siberian Lake.

Cyanobacteria from the genus Arthrospira/Limnospira are considered haloalkalotolerant organisms with optimal growth temperatures around 35 °C. They are most abundant in soda lakes in tropical and subtropical regions. Here, we report the comprehensive genome-based characterisation and physiological investigation of the new strain O9.13F that was isolated in a temperate climate zone from the winter freezing Solenoye Lake in Western Siberia. Based on genomic analyses, the Siberian strain belongs to the Arthrospira/Limnospira genus. The described strain O9.13F showed the highest relative growth index upon cultivation at 20 °C, lower than the temperature 35 °C reported as optimal for the Arthrospira/Limnospira strains. We assessed the composition of fatty acids, proteins and photosynthetic pigments in the biomass of strain O9.13F grown at different temperatures, showing its potential suitability for cultivation in a temperate climate zone. We observed a decrease of gamma-linolenic acid favouring palmitic acid in the case of strain O9.13F compared to tropical strains. Comparative genomics showed no unique genes had been found for the Siberian strain related to its tolerance to low temperatures. In addition, this strain does not possess a different set of genes associated with the salinity stress response from those typically found in tropical strains. We confirmed the absence of plasmids and functional prophage sequences. The genome consists of a 4.94 Mbp with a GC% of 44.47% and 5355 encoded proteins. The Arthrospira/Limnospira strain O9.13F presented in this work is the first representative of a new clade III based on the 16S rRNA gene, for which a genomic sequence is available in public databases (PKGD00000000).

Chromophorylation of a Novel Cyanobacteriochrome GAF Domain from Spirulina and Its Response to Copper Ions.

Cyanobacteriochromes (CBCRs) are phytochrome-related photoreceptor proteins in cyanobacteria and cover a wide spectral range from ultraviolet to far-red. A single GAF domain that they contain can bind bilin(s) autocatalytically via heterologous recombination and then fluoresce, with potential applications as biomarkers and biosensors. Here, we report that a novel red/green CBCR GAF domain, SPI1085g2 from Spirulina subsalsa, covalently binds both phycocyanobilin (PCB) and phycoerythrobilin (PEB). The PCB-binding GAF domain exhibited canonical red/green photoconversion with weak fluorescence emission. However, the PEB-binding GAF domain, SPI1085g2-PEB, exhibited an intense orange fluorescence (λabs.max = 520 nm, λfluor.max = 555 nm), with a fluorescence quantum yield close to 1.0. The fluorescence of SPI1085g2-PEB was selectively and instantaneously quenched by copper ions in a concentration-dependent manner and exhibited reversibility upon treatment with the metal chelator EDTA. This study identified a novel PEB-binding cyanobacteriochrome-based fluorescent protein with the highest quantum yield reported to date and suggests its potential as a biosensor for the rapid detection of copper ions.

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.

Structural, Dynamic, and Functional Characterization of a DnaX Mini-intein Derived from Spirulina platensis Provides Important Insights into Intein-Mediated Catalysis of Protein Splicing.

Protein splicing is a self-catalyzed post-translational modification in which the intein enzyme excises itself from a precursor protein and ligates the flanking sequences to produce a mature protein. We report the solution structure of a 136-residue DnaX mini-intein enzyme derived from the cyanobacterium Spirulina platensis. This sequence adopts a well-defined globular structure and forms a horseshoe-shaped fold commonly found in the HINT (hedgehog intein) topology. Backbone dynamics and hydrogen exchange experiments revealed conserved motions on various time scales, which is proposed to be a characteristic of the intein fold. Interestingly, several dynamic motions were found in symmetrically equivalent positions within the protein structure, which might be a consequence of the symmetrical intein fold. In cell splicing activity showed that Spl DnaX mini-intein is a highly active enzyme. The precursor protein was not detected at any timepoint of the assay. Apart from the splicing reaction, catalytic cleavage at the N- and C-termini of the precursor protein was also observed. To determine the roles of the catalytic residues in splicing and cleavage reactions, all combinations of alanine mutations of these residues were generated and functionally characterized. This in-depth analysis revealed cooperativity between these catalytic residues, which suppresses the N- and C-terminal cleavage reactions and enhances the yield of the spliced product. Overall, this study provides a thorough structural, dynamic, and functional characterization of a new intein sequence and adds to the collection of these unique enzymes that have found tremendous applications in biochemistry and biotechnology.

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.

Peroxiredoxin of Arthrospira platensis derived short molecule YT12 influences antioxidant and anticancer activity.

This study demonstrates both the antioxidant and anticancer potential of the novel short molecule YT12 derived from peroxiredoxin (Prx) of spirulina, Arthrospira platensis (Ap). ApPrx showed significant reduction in reactive oxygen species (ROS) against hydrogen peroxide (H2 O2 ) stress. The complementary DNA sequence of ApPrx contained 706 nucleotides and its coding region possessed 546 nucleotides between position 115 and 660. Real-time quantitative reverse transcription polymerase chain reaction analysis confirmed the messenger RNA expression of ApPrx due to H2 O2 exposure in spirulina cells at regular intervals, in which the highest expression was noticed on Day 20. Cytotoxicity assay was performed using human peripheral blood mononuclear cells, and revealed that at 10 µM, the YT12 did not exhibit any notable toxicity. Furthermore, ROS scavenging activity of YT12 was performed using DCF-DA assay, in which YT12 scavenged a significant amount of ROS at 25 µM in H2 O2 -treated blood leukocytes. The intracellular ROS in human colon adenocarcinoma cells (HT-29) was regulated by oxidative stress, where the YT12 scavenges ROS in HT-29 cells at 12.5 µM. Findings show that YT12 peptide has anticancer activity, when treated against HT-29 cells. Through the MTT assay, YT12 showed vital cytotoxicity against HT-29 cells. These finding suggested that YT12 is a potent antioxidant molecule which defends ROS against oxidative stress and plays a role in redox balance.

Intracellular oxidative damage due to antibiotics on gut bacteria reduced by glutathione oxidoreductase-derived antioxidant molecule GM15.

The human gut consists of > 1000 different bacterial species for the smooth functioning of the gut. In normal conditions, the antioxidant system present in cells minimize the effects of reactive oxygen species. Upon exposure to antibiotics, there is a rise in ROS level which induces oxidative stress to the cells, ultimately killing the cells. Two broad-spectrum antibiotics, streptomycin and gentamicin at a concentration of 50 µM and 25 µM, were treated with Bacillus subtilis SRMIST201901 (MN726522) and B. cereus SRMIST201902 (MN726923); the treatment reduced the cell counts. Considering the bacterial defense property which relies on the antioxidant mechanism, in this study, we have reported an antioxidant peptide (GM15) derived from glutathione oxidoreductase of spirulina (or called cyanobacteria) Arthrospira platensis (Ap) which reduced the intracellular oxidative stress. Cellular ROS detection was confirmed by fluorescent-associated cell sorting (FACS) using the DCFDA dye. Resazurin dye test also confirmed the activity of peptide on the growth of the Bacillus sp. Based on the results obtained, it was concluded that there was a significant (P < 0.05) reduction in the intracellular oxidative stress on treating with GM15 peptide. Overall, the study indicates the influence of antioxidant peptide on the intracellular oxidative stress, leading to the development of an antioxidant drug from glutathione oxidoreductase of A. platensis against oxidative-related stresses.

Brackish Groundwater from Brazilian Backlands in Spirulina Cultures: Potential of Carbohydrate and Polyunsaturated Fatty Acid Production.

The composition of brackish groundwater from Brazilian backlands contains important elements necessary for metabolism in microalgae. This study evaluated the use of 100% brackish groundwater with different amounts of Zarrouk nutrients for Spirulina sp. LEB 18 cultivation. The growth parameters and biomass composition, including the concentrations of proteins, carbohydrates, ash, lipids, and fatty acids, were evaluated. The best growth parameter results were obtained in the assay using 100% brackish groundwater and only 25% of Zarrouk nutrients, which were equal to those obtained for the control culture. The concentrations of carbohydrates and polyunsaturated fatty acids were increased by as much as 4- and 3.3-fold, respectively, when brackish groundwater was used in the cultures. The lipid profile demonstrated that the biomass had the potential for use in biodiesel production. The use of brackish groundwater is a sustainable, economical way to obtain high-quality biomass for different applications during Spirulina sp. LEB 18 cultivation.

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.

Oxygenic Phototrophs Need ζ-Carotene Isomerase (Z-ISO) for Carotene Synthesis: Functional Analysis in Arthrospira and Euglena.

For carotenogenesis, two biosynthetic pathways from phytoene to lycopene are known. Most bacteria and fungi require only phytoene desaturase (PDS, CrtI), whereas land plants require four enzymes: PDS (CrtP), ζ-carotene desaturase (ZDS, CrtQ), ζ-carotene isomerase (Z-ISO) and cis-carotene isomerase (CrtISO, CrtH). The gene encoding Z-ISO has been functionally identified in only two species, Arabidopsis thaliana and Zea mays, and has been little studied in other organisms. In this study, we found that the deduced amino acid sequences of Arthrospira Z-ISO and Euglena Z-ISO have 58% and 62% identity, respectively, with functional Z-ISO from Arabidopsis. We studied the function of Z-ISO genes from the cyanobacterium Arthrospira platensis and eukaryotic microalga Euglena gracilis. The Z-ISO genes of Arthrospira and Euglena were transformed into Escherichia coli strains that produced mainly 9,15,9'-tri-cis-ζ-carotene in darkness. In the resulting E. coli transformants cultured under darkness, 9,9'-di-cis-ζ-carotene was accumulated predominantly as Z-ISO in Arabidopsis. This indicates that the Z-ISO genes were involved in the isomerization of 9,15,9'-tri-cis-ζ-carotene to 9,9'-di-cis-ζ-carotene in darkness. This is the first functional analysis of Z-ISO as a ζ-carotene isomerase in cyanobacteria and eukaryotic microalgae. Green sulfur bacteria and Chloracidobacterium also use CrtP, CrtQ and CrtH for lycopene synthesis as cyanobacteria, but their genomes did not comprise Z-ISO genes. Consequently, Z-ISO is needed in oxygenic phototrophs, whereas it is not found in anoxygenic species.

Detailed characterization of the Arthrospira type species separating commercially grown taxa into the new genus Limnospira (Cyanobacteria).

The genus Arthrospira has a long history of being used as a food source in different parts of the world. Its mass cultivation for production of food supplements and additives has contributed to a more detailed study of several species of this genus. In contrast, the type species of the genus (A. jenneri), has scarcely been studied. This work adopts a polyphasic approach to thoroughly investigate environmental samples of A. jenneri, whose persistent bloom was noticed in an urban reservoir in Poland, Central Europe. The obtained results were compared with strains designated as A. platensis, A. maxima, and A. fusiformis from several culture collections and other Arthrospira records from GenBank. The comparison has shown that A. jenneri differs from popular species that are massively utilized commercially with regard to its cell morphology, ultrastructure and ecology, as well as its 16S rRNA gene sequence. Based on our findings, we propose the establishment of a new genus, Limnospira, which currently encompasses three species including the massively produced L. (A.) fusiformis and L. (A.) maxima with the type species Limnospira fusiformis.

Cytochrome P450-Catalyzed Hydroxylation Initiating Ether Formation in Platensimycin Biosynthesis.

Platensimycin (PTM) and platencin (PTN) are potent and selective inhibitors of bacterial and mammalian fatty acid synthases. The regio- and stereospecificity of the ether oxygen atom in PTM, which PTN does not have, strongly contribute to the selectivity and potency of PTM. We previously reported the biosynthetic origin of the 11 S,16 S-ether moiety by characterizing the diterpene synthase PtmT3 as a (16 R)- ent-kauran-16-ol synthase and isolating 11-deoxy-16 R-hydroxylated congeners of PTM from the Δ ptmO5 mutant. PtmO5, a cytochrome P450, was proposed to catalyze formation of the ether moiety in PTM. Here we report the in vitro characterization of PtmO5, revealing that PtmO5 stereoselectively hydroxylates the C-11 position of the ent-kaurane scaffold resulting in an 11 S,16 R-diol intermediate. The ether moiety, the oxygen of which originates from the P450-catalyzed hydroxylation at C-11, is formed via cyclization of the diol intermediate. This study provides mechanistic insight into ether formation in natural product biosynthetic pathways.

Two Classes of Pigments, Carotenoids and C-Phycocyanin, in Spirulina Powder and Their Antioxidant Activities.

Arthrospira platensis is the widely available source of spirulina that contains distinctive natural pigments, including carotenoids and C-phycocyanin (C-PC). In this study, the major carotenoid and C-PC contents were determined in seven commercially available spirulina powder products and laboratory-prepared A. platensis trichomes (AP-1) by an LC-DAD method and UV-Visible spectrometry, respectively. The correlation of these two pigment content levels with Hunter color coordinates and antioxidant activity was also evaluated. The L* value failed to show a significant correlation with pigment content, but a positive correlation was observed between a* values and the contents of total carotenoid and C-PC. As b* values decreased, the chlorophyll a and C-PC contents increased. AP-1 exhibited the highest content of total carotenoids, chlorophyll a and C-PC, and antioxidant activities among the samples. This observation could be related to degradation of these pigments during the mass production process. The carotenoid profiles suggested that the commercial spirulina powders originated from two different sources, A. platensis and A. maxima. Total carotenoid and C-PC content exhibited positive significant correlations with antioxidant activities measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. These results provide a strong scientific foundation for the establishment of standards for the commercial distribution of quality spirulina products.