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In cyanobacteria, phycobilisomes serve as peripheral light-harvesting complexes of the two photosystems, extending their antenna size and the wavelength range of photons available for photosynthesis. The abundance of phycobilisomes, the number of phycobiliproteins they contain, and their light-harvesting function are dynamically adjusted in response to the physiological conditions. Phycobilisomes are also thought to be involved in state transitions that maintain the excitation balance between the two photosystems. Unlike its eukaryotic counterpart, PSI is trimeric in many cyanobacterial species and the physiological significance of this is not well understood. Here we compared the composition and light-harvesting function of phycobilisomes in cells of Synechocystis sp. PCC 6803, which has primarily trimeric PSI, and the ΔpsaL mutant unable to form trimers. We also investigated a mutant additionally lacking the PsaJ and PsaF subunits of PSI. Both strains with monomeric PSI accumulated significantly more allophycocyanin per chlorophyll, indicating higher abundance of phycobilisomes. On the other hand, a higher phycocyanin:allophycocyanin ratio in WT suggests larger phycobilisomes or the presence of APC-less phycobilisomes (CpcL-type), that are not assembled in cells with monomeric PSI. Steady-state and time-resolved fluorescence spectroscopy at room temperature and 77 K revealed that PSII receives more energy from the phycobilisomes at the expense of PSI in cells with monomeric PSI, regardless of the presence of PsaF. Taken together, these results show that the oligomeric state of PSI has an impact on the excitation energy flow in Synechocystis.One-sentence summaryCyanobacterial mutants with monomeric PSI show changes in the composition and abundance of phycobilisomes and in the excitation energy transfer to PSII and PSI.

A single-step and rapid chromatographic method-based purification of Gracilaria corticata (J. Agardh) R-phycoerythrin (R-PE) was attained using polyacrylamide gel electrophoresis (PAGE) technique without affecting structural integrity. The purified R-PE had a characteristic UV–Vis spectrum with three absorbance maxima at 496, 535, and 565 nm, and fluorescence at 575 nm. R-PE was obtained with a purity index of 4.2 and a recovery yield of 44.3%. SDS-PAGE analysis exhibited three sub-units i.e., 18, 21, and 31 kDa, which corresponds to α, β, and γ, respectively. This report's purification process was considered less time-consuming and could be efficiently applied to purify phycobiliproteins. The purified R-PE showed optimal stability up to 6 h at pH 7.0 when exposed to light (3000 lx), while the temperature at which the maximum stability was retained was at 20 °C. The cellular imaging property of R-PE was effectively implemented to evaluate its credentials without affecting the cell proliferation of Vero and Hep-2 cell lines with the higher IC50 concentrations in vitro. Under fluorescence microscopy and flow cytometry analysis, purified R-PE displayed the characteristic affinity towards cell imaging functions in preliminary in vitro studies.

Aqueous two-phase systems (ATPS) stand out as an alternative technique for recovering and concentrating proteins. However, the study of ATPS to recover Arthrospira platensis protein is still poorly reported. This research used a sequential strategy of experimental design to evaluate the protein recovery from A. platensis protein extract using ATPS composed of polyethylene glycol (PEG: 1500, 4000, 6000, and 8000 Da) and saline solution (potassium phosphate and sodium citrate). The maximized conditions for A. platensis protein recovery were established by using 16% sodium citrate and 18% PEG 1500 Da, reaching 1.02 of purification factor and 75% protein recovery. Electrophoresis analysis showed protein bands between 5 and 15 kDa, characteristic size of phycobiliproteins. PEG and sodium citrate ATPS are a simple and low-cost alternative to the recovery A. platensis protein and show potential for industrial application.

Algae (both micro and macro) have gained huge attention in the recent past for their high commercial value products. They are the source of various biomolecules of commercial applications ranging from nutraceuticals to fuels. Phycobiliproteins are one such high-value low volume compounds that are mainly obtained from micro and macroalgae. In order to tap the bioresource, a significant amount of work has been carried out for large scale production of algal biomass. However, work on downstream processing aspects of phycobiliproteins (PBPs) from algae is scarce, especially in the case of macroalgae. There are many difficulties in cell wall disruption of both micro and macro algae because of their cell wall structure and compositions. At the same time, there are several challenges in the purification of phycobiliproteins. The current review article focuses on the recent developments in downstream processing of phycobiliproteins (mainly phycocyanins and phycoerythrins) from micro and macroalgae. The current status, recent advancements and potential technologies (that are under development) are summarised in this review article besides providing future directions for the present research area.

Phycobiliproteins are colored, active molecules with potential use in different industries. They are the union of proteins and bilins (Chromophores). The primary source of phycobiliproteins is algae; however, the traditional algae culture has production restrictions. The production in bacterial models can be a more efficient alternative to produce these molecules. However, the lack of knowledge in some steps of the phycobiliprotein metabolic pathway limits this alternative. Porphyridium cruentum is a single cell red alga with a high phycobiliprotein content. Its protein sequences were the basis for phycobilin production in this study. In this study, we cloned and characterized enzymes presumably involved in the chromophore production of P. cruentum. Using sequences obtained from its transcriptome, we characterized two cDNA sequences predicted to code respectively for a ferredoxin-dependent bilin reductase and a bilin lyase-isomerase. We expressed these enzymes in Escherichia coli to obtain in vivo evidence of their enzymatic activity on the substrate biliverdin IXα. Lastly, we analyzed them using thin-layer chromatography, spectrophotometry, and fluorescence spectroscopy. These experiments provided evidence of bilin modification. The expressed bilin lyase-isomerase did not show significant activity over the biliverdin molecule. On the contrary, the expressed ferredoxin-dependent bilin reductase showed activity over the biliverdin.

Kappaphycus alvarezii is a type of red seaweed (Rhodophyta) which contains phycobiliprotein pigments. Red seaweed is dominated by phycoerythrin type phycobiliprotein. Phycoerythrin can be obtained from the extraction process. The purpose of this study was to determine the effect of solvent type and acceleration time of ultrasonication extraction on phycoerythrin pigments. The extraction process was carried out in stages using distilled water, CaCl2 and phosphate buffer with ultrasonication acceleration of 35-55 minutes. The results showed that the phycoerythrin pigment extract of K. alvarezii using distilled water produced a more concentrated pigment color than buffer phosphate and CaCl2, showing the highest concentration of 0.057 mg/mL, and a purity index of 0.189. Water solvent is safe to use because water does not have toxic power. So, there is no need to conduct a preliminary test for solvent toxicity. It is more economical than other types of solvents. The extraction of phycoerythrin pigment using distilled water for 45 minutes resulted in a more concentrated pigment color. The concentration of phycoerythrin pigment before and after precipitation was 0.170 mg/mL and 0.421 mg/mL, respectively. The phycoerythrin pigment purity index before and after precipitation was 0.301 and 0.831, respectively. The best antioxidant activity (% inhibition) was found at concentrations of 50 ppm and 80 ppm phycoerythrin pigment with extraction time of 45 minutes at 62% and 89% respectively. Protein profile using SDS-Page showed that phycoerythrin has a molecular weight of 16.27 kDa in the subunit, 17.79 kDa in the subunit β, and 30.60 kDa in the subunit γ.

The cyanobacterium Leptolyngbya sp. KC45, as it originally occurs in hot springs, can be cultured at high temperatures and pH values, with high phycobiliprotein content. Although phycobiliprotein has been applied as a natural dye and fluorescent labelling agent, the application of illuminated colourants in food and beverages is still limited. This study showed the properties related to phycobiliprotein application in beverages, including physical stability, safety and some antioxidant capacity. When testing at the 2500 mg mL−1 concentration of pigment extract, Vero cell viability remained above the acceptable 50% level. Furthermore, microcystin-LR and microcystin-RR were not present according to HPLC detection test. The phycobiliprotein was stable at pH 3–7 at 4 °C in the dark for 1 month. It was also stable at a pH above 4.5 and an alcohol concentration below 30%. Illumination of phycobiliprotein in beverages under UV blacklight could be enhanced by Zn2+ ions and ethanol. Mixed with ethanol (below 40%), phycobiliprotein still showed in vitro antioxidant capacity such as ferric-reducing/antioxidant power, anti-lipid peroxidation and iron-chelating activity. Our results show that pigments from Leptolyngbya sp. KC45 can be applied as a health-enhancing illuminated colourant, which may be relevant for development in other food and beverage products.

Phycobiliproteins are a class of light-harvesting fluorescent proteins existing in cyanobacteria and microalgae, which harvest light and convert it into electricity. Owing to recent demands on environmental-friendly and renewable apparatuses, phycobiliproteins have attracted substantial interest in bioenergy and sustainable devices. However, converting energy from biological materials remains challenging to date. Herein, we report a novel scheme to enhance biological light-harvesting through light-matter interactions at the biointerface of whispering-gallery modes (WGMs), where phycobiliproteins were employed as the active gain material. By exploiting microdroplets as a carrier for light-harvesting biomaterials, strong local electric field enhancement and photon confinement at the cavity interface resulted in significantly enhanced bio-photoelectricity. A threshold-like behavior was discovered in photocurrent enhancement and the WGM modulated fluorescence. Systematic studies of biologically produced photoelectricity and optical mode resonance were carried out to illustrate the impact of the cavity quality factor, structural geometry, and refractive indices. Finally, a biomimetic system was investigated by exploiting cascade energy transfer in phycobiliprotein assembly composed of three light-harvesting proteins. The key findings not only highlight the critical role of optical cavity in light-harvesting but also offer deep insights into light energy coupling in biomaterials. Ministry of Education (MOE) Nanyang Technological University This research is supported by the Ministry of Education Singapore (Tier 1-RG 158/19(S)). We would like to thank Internal Grant NAP SUG -M4082308.040 from NTU.

Currently, the food additive industry has interest in replacing artificial dyes with natural pigments, trying to maintain consumer interest and increase their awareness towards healthy diets. Phycobiliproteins are light-harvesting and water-soluble proteins extracted from cyanobacteria and red algae that can be employed as natural additives. In the present work, a C-phycocyanin extract from the cyanobacterium Arthrospira platensis was tested as blue colorant in beverages to demonstrate that samples containing the protein extract have a color similar to marketed beverages containing synthetic dyes. Using spectroscopy and colorimetry, the extract was characterized and gave evidence of having good properties and good stability in the pH range between 3.0 and 9.0. The staining factors, representing the amount of blue protein needed to reproduce the color of bluish commercial samples, ranged between 15.6 and 111.7 mg·L−1, being sufficiently low in all samples. Additionally, color stability during a short period of cold storage was studied: it demonstrated that isotonic and tonic beverages remained stable throughout the 11-days analysis period with no significant changes. These results prove that the C-phycocyanin extract has potential applications in food as natural colorant, being an alternative option to synthetic coloring molecules.

Several strains of unicellular cyanobacteria from the culture collection of St. Petersburg State University, St. Petersburg, Russia (CALU), which were preliminary identified as Synechocystis sp., are reclassified in the new genus Altericista. Three new species are proposed, A. lacusladogae, A. violacea, and A. variichlora. The last species produces accessory chlorophylls d and f in cultures illuminated by far-red light, an attribute rarely observed in cyanobacteria, especially in unicellular strains. This genus is morphologically similar to Synechocysis having coccoid cells that divide in two successive planes at right angles, containing no sheath or capsule, and having the lamellar system represented by peripheral concentric thylakoids. Altericista shows ecological, biochemical, and physiological characters unlike those in Synechocystis and has the distinguishing phenotypic characters as follows: freshwater, non-halotolerant ecotype; palmitate and α-linoleate as major fatty acids; and the ability to photoacclimate, including several types of complementary chromatic adaptation. Genetic differences from Synechocystis sp. include 16S rRNA, rpoC1, and rbcL gene sequences, as well as sequence and folding of 16S-23S ITS.

Agriculture runoffs and discharge of wastewaters are the major causes of eutrophication. Although eutrophication could promote the thriving of any phytoplankter, harmful algal blooms (HABs) are dominated frequently by cyanobacteria. Currently, HABs dominated by the toxigenic cyanobacterium Microcystis aeruginosa in lakes and reservoirs are the main environmental concerns worldwide. This study aimed to determine how M. aeruginosa (Ma) modifies the population growth of Pseudokirchneriella subcapitata (Ps) and Ankistrodesmus falcatus (Af). Growth kinetics were determined for each species and in the combinations: Ps-Ma, Af-Ma, Af-Ps, and Ps-Af-Ma. At the end of experiments, photosynthetic pigments, phycobiliproteins, and microcystins were quantified. A logistic equation significantly described the growth trend for all of the tested species, enabling the identification of negative effects on early stages in the population growth of co-cultures with the cyanobacterium; in addition, the interaction effects on the growth rate and in the maximum attainable population density were determined. The biomasses of A. falcatus and P. subcapitata were significantly higher when cultured individually than in all of the combinations with the cyanobacterium. The concentrations of chlorophyll a and b, as well as carotenoids, were lower in combined cultures, but phycobiliprotein content in the cultures with M. aeruginosa was not significantly affected. Microcystis aeruginosa negatively affected the growth of the microalgae, but A. falcatus was significantly more inhibited than P. subcapitata; however, microcystin concentrations were significantly reduced in the co-cultures with microalgae. These results could help to explain the displacements of microalgae when cyanobacteria are present, giving rise to cyanobacterial blooms in eutrophic freshwaters.

A cyanobacterium of the genus Chroococcidiopsis has been recently unveiled to go to Mars, owing to its unique ability to stand harsh environmental conditions. Nevertheless, it has been little characterized in terms of other biotechnological applications. The aim of this study was thus to explore the biotechnological potential of Chroococcidiopsis sp. LEGE 06174, using GRAS (generally recognized as safe) solvents for the combined extraction of bioactive compounds. Due to its mucilaginous sheath, sulfuric acid, NaOH, PBS, DMSO 20%, DMSO 100%, and acetone were tested as preliminary treatment—in attempts to enhance pigment extraction. Extracts were then obtained by several series of successive extractions: phosphate-buffered saline (PBS) (serie A), ethanol-PBS (serie B), acetone-PBS (serie C), methanol-PBS (serie D), and acetone-methanol-PBS (serie E). Such extracts were screened for antioxidant capacity, cytotoxicity, and physicochemical characterization in terms of polysaccharides, pigments, and total phenolic compounds. Pre-treatment with PBS proved the most effective toward overall pigment extraction and dissolution of the said mucilaginous sheath. Chroococcidiopsis sp. extracts have unfolded some interesting bioactive features, particularly upon pre-treatment with PBS—i.e., high antioxidant capacity and high content in polysaccharides, scytonemin, phycobiliproteins, and phenolic compounds. The highest total pigment content was obtained in serie D, particularly carotenoids, whereas the highest level of phenolic compounds was found in serie B. All in all, Chroococcidiopsis sp. appears to constitute a significant biotechnological resource worthy of further exploitation in terms of high added-value compounds.

The tropical red seaweed Halymenia durvillei Bory de Saint Vincent is a potential source of the high-value pigments, r-phycoerythrin (RPE) and r-phycocyanin (RPC). The unique properties of these pigments find many applications—from food to cosmetics, pharmaceuticals, and biomedical research. This study aimed to improve the land-based culture technology of H. durvillei by determining the appropriate combination of light, water motion, and stocking density that would result in high growth performance and high RPE and RPC content. Combinations of two light levels (full light, 100% and reduced light, 67%), two water motion levels (low and moderate), and three stocking densities (50, 100, and 200 g) were studied using 64.5-L glass tanks with flow-through seawater and aeration systems at the outdoor land-based seaweed nursery in Bolinao, Pangasinan, Philippines. After 6 weeks of culture, growth performance (growth rate and productivity) of H. durvillei and phycobiliprotein content were best under a combination of full light (100%), moderate water motion, and 50-g stocking density. The generally low light regime during the experimental period, which coincided with the cold, dry season characterized by shorter days and overcast skies, may have influenced H. durvillei to maximize the use of available resources such as light and possible increased nutrient availability from water motion to promote growth and phycobiliprotein synthesis. Treatments with low stocking densities generally showed satisfactory growth and phycobiliprotein content. This study provides groundwork for future research into mechanisms by which these and other factors affect the growth and physiology of H. durvillei in culture.

Phycobilisomes (PBSs) are extremely large chromophore–protein complexes on the stromal side of the thylakoid membrane in cyanobacteria and red algae. The main function of PBSs is light harvesting, and they serve as antennas and transfer the absorbed energy to the reaction centers of two photosynthetic systems (photosystems I and II). PBSs are composed of phycobiliproteins and linker proteins. How phycobiliproteins and linkers are organized in PBSs and how light energy is efficiently harvested and transferred in PBSs are the fundamental questions in the study of photosynthesis. In this review, the structures of the red algae Griffithsia pacifica and Porphyridium purpureum are discussed in detail, along with the functions of linker proteins in phycobiliprotein assembly and in fine-tuning the energy state of chromophores.

Dye-sensitized solar cells have been of great interest in photovoltaic technology due to their capacity to convert energy at a low cost. The use of natural pigments means replacing expensive chemical synthesis processes by easily extractable pigments that are non-toxic and environmentally friendly. Although most of the pigments used for this purpose are obtained from higher plants, there are potential alternative sources that have been underexploited and have shown encouraging results, since pigments can also be obtained from organisms like bacteria, cyanobacteria, microalgae, yeast, and molds, which have the potential of being cultivated in bioreactors or optimized by biotechnological processes. The aforementioned organisms are sources of diverse sensitizers like photosynthetic pigments, accessory pigments, and secondary metabolites such as chlorophylls, bacteriochlorophylls, carotenoids, and phycobiliproteins. Moreover, retinal proteins, photosystems, and reaction centers from these organisms can also act as sensitizers. In this review, the use of natural sensitizers extracted from algae, cyanobacteria, bacteria, archaea, and fungi is assessed. The reported photoconversion efficiencies vary from 0.001 % to 4.6 % for sensitizers extracted from algae and microalgae, 0.004 to 1.67 % for bacterial sensitizers, 0.07-0.23 % for cyanobacteria, 0.09 to 0.049 % for archaea and 0.26-2.3 % for pigments from fungi.

Background. Cyanobacterium Arthrospira (Spirulina) platensis has a unique biochemical composition and is widely used in various fields, including medicine and agriculture. The main phycobiliproteins (PBPs) of spirulina – C-phycocyanin and allophycocyanin protect animal cells from oxidative stress and mitochondrial dysfunction. At the same time there is little information about the antioxidant properties of PBPs in a plant cell and their influence on the bioenergetic parameters of plant mitochondria. Purpose. The aim of this study was to determine the effect of A. platensis PBPs extract on glucose oxidase activity and functioning of potato mitochondria. Materials and methods. PBPs were isolated from the crude biomass of A. platensis (Nordstedt) Gomont (strain IBSS-31) using cold extraction and precipitation with acetone. The protein extract with a high proportion of C-phycocyanin was used at concentrations of 0,025 – 0,25 mg/ml. The antioxidant properties of PBPs were evaluated by the inhibition of the glucose oxidase activity of potato extracts with increased expression of the GOX gene. The oxidative and phosphorylating activity of mitochondria in the presence of PBPs was measured by the polarographic method. Statistical data processing was carried out using SigmaPlot v. 14.0. Results. The glucose oxidase test revealed the antioxidant activity of the PBPs extract, which was pronounced at a concentration of 0,25 mg / ml. At the same concentration, the extract caused uncoupling of oxidation and phosphorylation in potato mitochondria during succinate oxidation, associated with an increase in the state 4 respiration rate and a decrease of the respiratory control coefficient. Conclusion. Thus, phycobiliproteins of A. platensis in a concentration-dependent manner reduce the generation of hydrogen peroxide in the glucose oxidase test system and cause uncoupling of the oxidation and phosphorylation in the plant mitochondria.

A separation process was established to sequentially fractionate and recover three anti-inflammatory components derived from sugars, phycobiliprotein, and chlorophyll from the hot-air-dried thalli of the red alga dulse (Palmaria palmata). The developed process consisted of three steps, without the use of organic solvents. In Step I, the sugars were separated by disrupting the cell wall of the dried thalli with a polysaccharide-degrading enzyme, and a sugar-rich extract (E1) was obtained by precipitating the other components, which were simultaneously eluted by acid precipitation. In Step II, the residue suspension from Step I was digested with thermolysin to obtain phycobiliprotein-derived peptides (PPs), and a PP-rich extract (E2) was obtained by separating the other extracts using acid precipitation. In Step III, solubilized chlorophyll was obtained by heating the residue, which was acid-precipitated, neutralized, and re-dissolved to concentrate the chlorophyll-related components (Chls)-rich extract (E3). These three extracts suppressed inflammatory-cytokine secretion by lipopolysaccharide (LPS)-stimulated macrophages, confirming that the sequential procedure had no negative effects on the activities of any of the extracts. The E1, E2, and E3 were rich in sugars, PPs, and Chls, respectively, indicating that the anti-inflammatory components were effectively fractionated and recovered through the separation protocol.

In this study, we assessed the effects of 11-day exposure of sulfadiazine (SD), sulfamethazine (SM2), norfloxacin (NOR), and enrofloxacin (ENR) on the growth, chlorophyll a (Chl. a) content, phycobiliproteins (PBPs) content, and alkaline phosphatase (ALP) activity of Chrysosporum ovalisporum, examined the removal rate of these antibiotics by C. ovalisporum, and performed acute toxicology test with Daphnia magna to determine the effect of interaction between antibiotics and cyanobacteria on aquatic animals. The results showed that the stress of SD and SM2 increased extracellular ALP activity and weakly inhibited the algal growth and the contents of Chl. a and PBPs compared with that noted in the control. ENR and NOR treatment groups exerted significant inhibition on algal growth as well as Chl. a and PBPs contents and ALP activity, although the cyanobacterium could degrade these two antibiotics more than SD and SM2. The results also revealed that the interaction between antibiotics and cyanobacteria could inhibit D. magna feeding.

The present work was designed for the biosynthesis of silver nanoparticles (AgNPs) by Spirulina platensis and Nostoc linckia phycobiliprotein extract and for evaluation of their antimicrobial, antioxidant, and antiviral activities. The biosynthesized AgNPs were characterized by UV-Vis spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, X-ray diffraction analysis, and Zeta potential analysis. The antimicrobial activity of the biosynthesized AgNPs was tested by the disk diffusion method. The antioxidant activity of the nanoparticles was assessed by using DPPH radical scavenging, total antioxidant capacity, and ferric reducing antioxidant assays. The antiviral activity of AgNPs was also challenged with the hepatitis C virus (HCV). The appearance of the surface plasmon resonance band at 420 nm indicated the biosynthesis of AgNPs. TEM images revealed that AgNPs had a mean average size of 21.211 and 21.052 nm for S. platensis and N. linckia, respectively. XRD analysis confirmed its spherical crystalline shape, and FTIR analysis suggested that proteins were responsible for their capping and stabilization. Zeta potential recorded − 15.902 mV and − 16.811 mV for S. platensis and N. linckia AgNPs, respectively, confirming its stability. AgNPs showed potent antimicrobial activity against some bacterial pathogens and Candida albicans. The antioxidant activity of AgNPs was evident by the use of three antioxidant assays. Significant antiviral activity against HCV (64.976%) was recorded for AgNPs of N. linckia, compared with Ribavirin (66.673%) as a standard drug, while S. platensis AgNPs recorded 48.334%. In conclusion, AgNPs biosynthesized from cyanobacterial phycobiliproteins were stable and showed potent antimicrobial, antioxidant, and antiviral activities.

The red pigment B-phycoerythrin (B-PE) belongs to the group of phycobiliproteins (PBPs). It is a part of the light-harvesting pigment complex of the red microalga Porphyridium purpureum (Bory) Drew et Ross, and its amount in cells is determined by the level of irradiation and nitrogen supply. B-PE is a valuable natural pigment whose biotechnological potential is used in nutraceuticals, pharmaceuticals, food and cosmetic industries, and in biomedical research and clinical diagnostics. The dynamics of cell number and the content of photosynthetic pigments are quite often assessed in experiments with P. purpureum. The culture’s density is low in the majority of the experiments, although it is known that it can reach 10 g/L of dry matter. The aim of the study was to investigate the features of the accumulation and production of PBPs in a dense culture of P. purpureum under varying illumination. The molecular-genetic analysis confirmed the taxonomic affiliation of P. purpureum culture. Algae were grown in flat plate photobioreactors with an average illumination of 5, 10, and 15 klx. The dynamics of culture density, the content of B-PE, and production characteristics were used as indicators. It was shown that an increase in the microalgae culture density corresponding to the calculated nitrogen concentration in the nutrient medium was obtained only under illumination of 5 klx. Illumination increased to 10, and 15 klx caused a decrease in both the maximum and average productivities of the culture by 2.5–3.5 times. It was experimentally shown that the highest content of B-PE in the cells and culture of P. purpureum (5.5% of dry matter and 74 mg/L, respectively) was observed under illumination of 5 klx. The pattern of the change in B-PE content in P. purpureum culture was determined depending on the specific illumination of microalgae cells: the pigment concentration hyperbolically decreased with increasing specific illumination. Thus, the level of illumination of P. purpureum microalgae cells had a significant effect on the growth characteristics of the culture (growth rate, B-PE synthesis rate and yield): a lower level of surface illumination was preferred for P. purpureum cultivation. The approach proposed in the study allows one to reduce material costs during the cultivation of P. purpureum while maintaining a high growth rate of the culture.

Light, or visible radiation, serves as a source of energy for photosynthesis of plants and most algae. In addition, light and ultraviolet radiation (UV-A and UV-B) act as a biological signal, triggering several cellular processes that are mediated by photoreceptors. The aim of this study was to evaluate the physiological and biochemical responses of Osmundea pinnatifida driven by different radiations through putative photoreceptors. For this, O. pinnatifida was grown under different radiation treatments composed by high intensity of light emitted by a low pressure sodium lamp (SOX), aiming to saturate photosynthesis, which was supplemented by low intensities of visible (red, green and blue) and ultraviolet radiation (UV-A and UV-B), in order to activate photoreceptors. Growth rates, photosynthesis, antioxidant activity, polyphenols, soluble proteins, phycobiliproteins, mycosporine-like amino acids (MAAs) and carotenoids were evaluated during the experiment. Complementary UV-A radiation positively influenced growth rates after 15 days of experiment, although the presence of a peak of blue light in this treatment can also have contributed. UV-B radiation increased the concentration of zeaxanthin and chlorophyll a. The blue light caused the accumulation of chlorophyll a, violaxanthin, phycoerythrin and polyphenols on different days of the experiment. Phycoerythrin also increased under green and red light conditions. Our results showed that some compounds can be modulated by different radiation, and the involvement of photoreceptors is suggested. In red algae, photoreceptors sensitive to red, green and blue light have been identified, however little is known about UV photoreceptors. The presence of photoreceptors sensitive to UV radiation in O. pinnatifida is discussed.

The paper studies the possibility of bioconversion of waste water from recirculating aquaculture systems (RAS). For this purpose, cyanobacteria Nostoc linckia (Roth.) Born. et Flah. was grown on waste water from RAS. In the process of cultivation, indicators of total mineralization, pH, and culture density were monitored. In the waste water, the content of various forms of nitrogen (NH4+, NO3-, NO2-), the content of P and S before and after the growth of cyanobacteria were determined It was noted that as a result of growing N. linckia in RAS waste water, a decrease in the content of various forms of nitrogen, sulfur and phosphorus is observed. Also, the content of phosphates decreased from 35×10-3 to 5×10-3 mg.L-1 and the content of sulfates from 95×10-3 to 25×10-3 mg.L-1. Moreover, the resulting biomass of cyanobacteria contained 57 % of proteins, 20 % of lipids and 11% of carbohydrates. It was found that N. linckia biomass is a promising source of phycobiliprotein pigments: phycocyanin, allophycocyanin and phycoerythrin.

Phycocyanin is a light-blue water-soluble natural pigment with wide application in fields including pharmaceutical, cosmetic and food industry. Arthrospira platensis is considered a natural bio-factory for obtaining phycocyanin, and although suitable cultivation conditions can enhance the pigment content, the importance of extraction and purification should not be overlooked, because the chemicals used in those steps can affect the quality of phycocyanin. Further, changes in temperature, or approaches used to extract other protein types from biomass, have been reported to degrade phycocyanin, influencing its final quality, while also contributing to higher energy consumption in the extraction process. Hence, this work compares several approaches for phycocyanin extraction, and analyzed the effects of changes in operating conditions, such as exposure time, application of solvent buffer, and ultrasonication, on the extraction yield, the extracts purity, and the process energy use efficiency. Experimental results point to promising improvements in the extraction yield with high purity of phycocyanin (44.24 mg/g with purity ratio of 0.34), when suitable operating parameters were used (2 h exposure to potassium phosphate buffer with 20 min of ultrasonication).

Noninvasive fluorescent imaging requires far-red and near-infrared fluorescent proteins for deeper imaging. Near-infrared light penetrates biological tissue with blood vessels due to low absorbance, scattering, and reflection of light and has a greater signal-to-noise due to less autofluorescence. Far-red and near-infrared fluorescent proteins absorb light >600 nm to expand the color palette for imaging multiple biosensors and noninvasive in vivo imaging. The ideal fluorescent proteins are bright, photobleach minimally, express well in the desired cells, do not oligomerize, and generate or incorporate exogenous fluorophores efficiently. Coral-derived red fluorescent proteins require oxygen for fluorophore formation and release two hydrogen peroxide molecules. New fluorescent proteins based on phytochrome and phycobiliproteins use biliverdin IXα as fluorophores, do not require oxygen for maturation to image anaerobic organisms and tumor core, and do not generate hydrogen peroxide. The small Ultra-Red Fluorescent Protein (smURFP) was evolved from a cyanobacterial phycobiliprotein to covalently attach biliverdin as an exogenous fluorophore. The small Ultra-Red Fluorescent Protein is biophysically as bright as the enhanced green fluorescent protein, is exceptionally photostable, used for biosensor development, and visible in living mice. Novel applications of smURFP include in vitro protein diagnostics with attomolar (10−18 M) sensitivity, encapsulation in viral particles, and fluorescent protein nanoparticles. However, the availability of biliverdin limits the fluorescence of biliverdin-attaching fluorescent proteins; hence, extra biliverdin is needed to enhance brightness. New methods for improved biliverdin bioavailability are necessary to develop improved bright far-red and near-infrared fluorescent proteins for noninvasive imaging in vivo.

Cyanobacteria are photosynthetic autotrophic aquatic prokaryotes. One of the methods for controlling cyanobacterial blooms is to destroy the phycobiliproteins required for photosynthesis. In this study, to improve the biodegradation of the fluoroquinolones through inhibit cyanobacteria, the molecular docking scores of 32 fluoroquinolones (FQs) with four categories of phycobiliproteins from cyanobacteria were calculated after sine normalization to characterize the binding ability between them. A two-dimensional quantitative structure-activity relationship (2D-QSAR) model was constructed based on the comprehensive scores. Danofloxacin (DAN) with the highest comprehensive score was chosen for molecular modification. When docking with four categories of phycobiliproteins from cyanobacteria, the docking values of DAN-11 and DAN-16 were increased up to 35.75%. Moreover, their functional characteristics and environmentally friendly predictive values were improved. When the DAN-11 and DAN-16 molecules docked with the other cyanobacterial phycobiliproteins, indicating that the designed DAN derivatives had general applicability to poison cyanobacteria, the weak interaction forces might increase the binding ability between the DAN derivatives and the receptor phycobiliprotein compared with the target molecule.

Significant levels of polycyclic aromatic hydrocarbons (PAHs) were detected in lakes. The competition between algae would be disturbed by PAHs resulted in variations of algal growth. For controlling the cyanobacterial blooms, it is important to understand this disturbed competition between Microcystis aeruginosa and other algae. A 6-day cultivation experiment was designed to investigate the responses of M. aeruginosa to PAHs in presence of green algae. A popular green alga Chlorella pyrenoidosa was used as a representative of green algae, and phenanthrene and pyrene were selected as representatives of PAHs. The results showed that M. aeruginosa outcompeted C. pyrenoidosa under PAH contamination, and PAHs and M. aeruginosa significantly inhibited the survival of C. pyrenoidosa. PAHs disturbed the growth of algae by influencing photosynthetic pigments and phycobiliproteins, and the different alteration of Fv/Fm ratios implied that shifted algal community composition would be induced by PAHs. The Fv/Fm of the two algal mixture and individual C. pyrenoidosa was significantly negatively correlated with phenanthrene levels. However, there were no significant correlations between the Fv/Fm of M. aeruginosa and the exposure levels of phenanthrene or pyrene. Remarkably, the Fv/Fm significantly increased in M. aeruginosa at 0.15 mg L-1 pyrene, suggesting that PSII resistance to pyrene was enhanced in M. aeruginosa. Our results pointed out an increasing frequency and intensity of cyanobacterial blooms could be induced by PAHs in contaminated waters.

Phycobilisomes (PBS), the major light-harvesting antenna in cyanobacteria, are supramolecular complexes of colorless linkers and heterodimeric, pigment-binding phycobiliproteins. Phycocyanin and phycoerythrin commonly comprise peripheral rods, and a multi-cylindrical core is principally assembled from allophycocyanin (AP). Each AP subunit binds one phycocyanobilin (PCB) chromophore, a linear tetrapyrrole that predominantly absorbs in the orange-red region of the visible spectrum (600–700 nm). AP facilitates excitation energy transfer from PBS peripheral rods or from directly absorbed red light to accessory chlorophylls in the photosystems. Paralogous forms of AP that bind PCB and are capable of absorbing far-red light (FRL; 700–800 nm) have recently been identified in organisms performing two types of photoacclimation: FRL photoacclimation (FaRLiP) and low-light photoacclimation (LoLiP). The FRL-absorbing AP (FRL-AP) from the thermophilic LoLiP strain Synechococcus sp. A1463 was chosen as a platform for site-specific mutagenesis to probe the structural differences between APs that absorb in the visible region and FRL-APs and to identify residues essential for the FRL absorbance phenotype. Conversely, red light-absorbing allophycocyanin-B (AP-B; ~ 670 nm) from the same organism was used as a platform for creating a FRL-AP. We demonstrate that the protein environment immediately surrounding pyrrole ring A of PCB on the alpha subunit is mostly responsible for the FRL absorbance of FRL-APs. We also show that interactions between PCBs bound to alpha and beta subunits of adjacent protomers in trimeric AP complexes are responsible for a large bathochromic shift of about ~ 20 nm and notable sharpening of the long-wavelength absorbance band.

Molecular and microscopic studies were performed to identify Chroococcidiopsis sp., an endolithic cyanobacterium, isolated from gypsum rocks of Atacama Desert (Chile). It was adapted to grow in mineral liquid medium, with 9 mM nitrate, bubbled with CO-enriched air (2.5 % v/v), and continuously illuminated with a white light of 70 μmol photons m s. The obtained biomass (productivity of 0.21 g L d) had a C/N ratio of 6.67, and it contained carbohydrates (45.40 % of dry weight), proteins (36.72 %), lipids (5.60 %) nucleic acids (3.90 %) and ashes (8.28 %). The lipid fraction was particularly rich in palmitic (29.86 % of total fatty acids), linoleic (18.20 %), palmitoleic (12.75 %), linolenic (10.92 %), stearic (9.64 %) and capric acid (6.29 %). Chroococcidiopsis sp. accumulated phycobiliproteins in a light-dependent process and produced 204 mg g, under incident light of 10 μmol photons·m·s, with a relative abundance of 40.9 % for phycocyanin, 23.3 % for phycoerythrin, and 35.8 % for allophycocyanin. The biomass from this cyanobacterium can be a good source of these pigments, especially APC (maximum of 95 mg g dw), which are of interest for pharmacological, cosmetic, and food industries., This work was funded by MCIU/AEI (Spain) and FEDER (UE) (grantreference PGC2018–094076-B-I00) and by a PhD-Grant from the R&DPlan of the University of Huelva, Spain, for Zaida Montero.

This study explored the effects of four drying methods, namely vacuum freeze-drying (VFD), hot-air drying (HD), microwave drying (MD) and shade drying (SD) on the sensory quality, amino acids composition, phycobiliproteins structure and rehydration rate of Porphyra haitanensis. It showed that VFD dried P. haitanensis had the highest protein (35.44 ± 0.87%), polysaccharide (18.91 ± 0.64%), umami amino acids (484.67 ± 5.03 mg/100 g, dry weight) and essential amino acids (9.89 ± 0.27 g/100 g, dry weight) than another three dried products. Drying affected secondary structure of phycobiliproteins, and the phycobiliproteins from VFD laver contained the most α-helix structure and the least random coil. In addition, VFD processed laver was rich in water-soluble polysaccharides and hydrophilic amino acids, which resulted in its quick rehydration and high-water absorption capacity. The results showed that VFD was suitable for producing high-quality P. haitanensis with excellent flavor and high contents of nutritional compounds.

Phycocyanin (PC) is one of the phycobiliproteins, pigments found in cyanobacteria, which can be used as natural dyes, antioxidants and fluorescent markers. This study aimed to investigate the effect of supplementation of the basal culture medium (BG110) of the cyanobacterium Anabaena variabilis with different sources of organic carbon in concentration of 1 g?L-1, evaluating the production of biomass and PC. The best condition obtained was the medium supplemented with glucose that produced 75.36 mg?g-1 PC, about 5 times greater than the control with 14.57 mg?g-1 PC. All supplemented media also showed higher biomass production compared to the basal medium, again to stand out for the glucose medium, presenting 0.29 g?L-1 of dry biomass. A ficocianina (FC) é uma das ficobiliproteínas, pigmentos encontrados nas cianobactérias, que podem ser usadas como corantes naturais, antioxidantes e marcadores fluorescentes. Este estudo teve como objetivo investigar o efeito da suplementação do meio de cultura basal (BG110) da cianobactéria Anabaena variabilis com diferentes fontes de carbono orgânico em concentração de 1 g?L-1, de modo a avaliar à produção de biomassa e FC. A melhor condição obtida foi o meio suplementado com glicose que produziu 75,36 mg?g-1 FC, cerca de 5 vezes maior que o controle com 14,57 mg?g-1 FC. Todos os meios suplementados também apresentaram maior produção de biomassa em comparação com o meio basal, novamente para destaque para o meio com glicose, apresentando 0,29 g?L-1 de biomassa seca.

R-phycoerythrin and R-phycocyanin are the main light-harvesting pigment-protein complexes in Pyropia yezoensis. They have bright colors and a high degree of fluorescence, and are now widely used in biomedicine, food, and cosmetic industries. Therefore, membrane chromatography was used to isolate and purify phycobiliprotein from P. yezoensis. Algal cells were disrupted by repeated freeze-thaw cycles. Then ammonium sulfate was added into the crude phycobiliprotein extract, so that the saturation of ammonium sulfate in the solution reached 20%, 30%, and 40% in sequence. At 30% and 40% ammonium sulfate saturation, precipitates of R-phycoerythrin and R-phycocyanin mixture in different proportions were obtained. The precipitates were ultra-filtrated to remove the salt, and then, the retentate was taken for membrane chromatographic treatment. In the membrane chromatographic treatment, salt-sensitive PVDF (polyvinyl difluoride) membranes were used for the follow-up experiments. By adjusting the concentration of ammonium sulfate, the membrane system changed the binding strength of various proteins, and then separated different types of phycobiliproteins. The final products of R-phycoerythrin (Aλmax/A280 purity 4.25, yield 45%) and R-phycocyanin (two purity grades: purity 5.8, yield 14.70% and purity 4.18, yield 39.89%) were obtained and then characterized by spectrophotometric and fluorometric measurements and SDS-PAGE. However, the large-scale production of R-phycocyanin and R-phycoerythrin remains a bottleneck as the column chromatography is difficult to be applied for industrial production. This method avoids the problem of easy clogging of column chromatography and can be useful for mass-production of R-phycoerythrin and R-phycocyanin in the future based on the laboratory results.

Spirulina maxima is a blue-green microalga that rich in pigment. The pigments in S. maxima grouped into primary pigment (Chlorophyll a) and accessory pigments (carotenoid & phycobiliprotein). Phycocyanin is an accessory pigment that belongs to phycobiliprotein, blue colored, and can be used as natural food coloring and drugs. Phycocyanin has activities as antibacterial, antioxidant, anti-inflammatory, antihyperalgesic, and many more. Because of that, phycocyanin usually used in the pharmaceutical industry. However, phycocyanin is a protein that unstable under lights, high temperature, and pH in the storage. This study aims to obtain information about the effect of pH on the stability of phycocyanin extracted from S. maxima that cultivated in indoor and semi-outdoor. The steps are cultivation, extraction using different solutions to get blue pigment phycocyanin, and stability test. Phycocyanin was dissolved in a buffer solution at pH 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, and 7.0 for 7 days. Color observations based on visualization and concentration measurements are carried out every day to see changes in phycocyanin. Growth in indoor cultivation with 24 hours light is faster than semi-outdoor a that uses only sunlight. Cultivation gets the optical density value 0,6 at day 20 with indoor cultivation and day 34 with semi-outdoor cultivation. Results show that phycocyanin can be extracted using a buffer phosphate solution. The stability of the pigments can be seen from the color changes and relative concentration using a spectrophotometer. Phycocyanin shows stable in the storage of pH 4 until pH 5.5. The highest relative concentration (CR) was shown in pH 5.

Cyanobacteria represent the richest sources of phycobiliproteins with especial reference to C-phycocyanin (C-PC), which in turn holds exhaustive therapeutic implications. Screening of several cyanobacterial strains namely Anabaena sp., Nostoc muscorum, Cylindrospermum sp., Plectonema sp., Scytonema sp., Spirulina sp., Synechococcous sp. and Tolypothrix sp. was carried out for their C-PC producing capacity, however the produced quantity of C-PC varies greatly among different strains. Owing to the crucial role of different media constituents on productivity of C-PC the current study was designed to optimize most appropriate media composition for augmented CPC production by selected superior producer. 36 factorial central composite design (CCD) dependent response surface methodology (RSM) was utilized to estimate the important medium components attributed with influencing C-PC productivity. RSM analysis of five independent coded factors including Na2CO3, K2HPO4, NaNO3, citric acid and EDTA were analyzed preceded by recognition of efficient variables for algal components production by Plectonema sp. Investigation of results revealed that the eminent medium components were NaCO3 (0.4 g/L); NaNO3 (0.5 g/L); K2HPO4 (2.8 g/L); citric acid (0.08 g/L) and EDTA (0.01 g/L) respectively. The optimized combination yielded 0.5536 mg/ml of C-PC. The increment of C-PC yield is R-Sq = 88.2%. Thus, our study led to the recognition of critical nutritional component that can be used further for enhanced productivity of C-PC.

Cyanobacteria are able to absorb light over a wide spectral range due to the presence of photoreceptors, making it possible to modulate the production of high-value compounds by inducing specific pathways. In order to evaluate the influence of light quality in cyanobacteria metabolism, Cyanobium sp. was grown in five different light conditions, by using low-pressure sodium vapor lamp (SOX) supplemented with low irradiances of green, red, and blue light and UV radiation compared to a control with only SOX. The effects of light supplementation on biomass productivity, photosynthetic activity, biochemical composition, and total antioxidant capacity were evaluated. No changes in biomass productivity were induced by any light supplements. The supplementation of red light triggered the production of lipids, phycocyanin, carotenoids, and total antioxidant compounds, while supplementation of green light increased the content of carbohydrates and chlorophyll a. Thus, supplementation of blue light and UV radiation showed little or no improvements to the culture, whereas under UV radiation the photosynthetic activity was reduced. Overall, Cyanobium sp. is a promising strain, mainly due to its accessibility to metabolism photoregulation as to produce various bioactive compounds. This work was financially co-supported by the COST Action ES1408 European network for algal bioproducts (EUALGAE); by the ZEBRALGRE (PTDC/CVT-WEL/5207/2014), funded by national funds through FCT supported by COMPETE 2020: POCI-01-0145-FEDER-016797; and by the strategical funding from FCT (UIDB/04423/2020 and UIDP/04423/2020) and the Atlantic Interreg Project - Enhance MicroAlgae - High added-value industrial opportunities for microalgae in the Atlantic Area (EAPA_338/2016). We also acknowledge the Junta de Andalucía for financing the RNM295 research group in University of Malaga.

Blue-green microalgae are the source of many commercially important products such as protein, amino acids, fatty acids, carotenoids and phycobiliproteins, and biotechnological studies on this issue has been profoundly increasing.Arthrospira (Spirulina) platensisis the main source of cyanobacterial phycocyanin, used as a natural colorant that is called as "Lina blue" in the commercial area. The purity ratio and quantity of phycocyanin may vary depending on the processing method, also the purity of the phycocyanin is an important factor that determines its application area. Food-grade phycocyanin is utilized safely as a natural dye in the food formulation without offering health risk. Many conventional methods are used in several to obtain crude extracts of C-PC, such as freezing and thawing, sonication and mechanical disruption. Also, for the purification stage high-speed centrifugation, precipitation with ammonium sulphate, and ion-exchange chromatography methods are used. The aim of this study is to investigate the effects of a modified and combined extraction and purification method, including precipitation, chilling and centrifugation, at different centrifuge speeds, temperature and time on phycocyanin concentration to obtain a food grade phycocyanin fromSpirulina platensis. As a result, centrifugation at 25 °C was found the higher purity ratio, above 0.7.

The feasibility of the semi-continuous cultivation of Arthrospira (Spirulina) sp. and Nostoc sp. PCC 7413, using the centrate from the anaerobic digestion of wastewater from a seafood canning industry as a nutrient source, was assessed. Semi-continuous cultures were carried out in aerated tubular culture units of 250 mL by replacing a 10–20% of the volume with the centrate every 2 days. Growth, ammonium, and nitrate removal were monitored, as well as phycobiliprotein and protein production by Arthrospira sp. and released exopolysaccharides production by Nostoc sp. PCC 7413. The ammonium removal efficiency by Arthrospira sp. was 84.9 ± 1.9% in a culture maintained with an ammonium concentration of 11.3 mM. Lower ammonium concentrations (4.9 mM) could be applied to Nostoc sp. PCC 7413, reaching similar relative removal efficiency (84.1%). Taking into account the high ammonium stripping that occurs at the high pH required in Arthrospira sp. cultures, results indicate a better nutrient removal by Nostoc sp., although Arthrospira sp. is more suitable for working at high ammonium concentrations. Since all the ammonium was removed during the first 24 h for both species, much lower residence time could be supported by the cultures. High concentrations of protein (2.5 ± 0.2 mg mL−1), phycobiliprotein (allophycocyanin, 84.3 ± 10.2 mg g−1; phycocyanin, 73.7 ± 7.7 mg g−1) were obtained by Arthrospira sp. cultures. A high concentration of released exopolysaccharides (962.7 ± 26.7 mg L−1) was also obtained for Nostoc sp. PCC 7413 when cultured in the anaerobic centrate. The results indicate the possibility of the use of filamentous cyanobacteria for the treatment of industrial effluents rich in ammonium, with different possibilities of valorization of the biomass produced.

Cyanobacteria are a group of microorganisms that have been studied for pigment production. Among these pigments, phycobiliproteins, especially the phycocyanin (PC), of blue color, are found in grea...

The light-harvesting phycobilisome complex is an important component of photosynthesis in cyanobacteria and red algae. Phycobilisomes are composed of phycobiliproteins, including the blue phycobiliprotein phycocyanin, that are considered high-value products with applications in several industries. Remarkably, several cyanobacteria and red algal species retain the capacity to harvest light and photosynthesise under highly selective environments such as hot springs, and flourish in extremes of pH and elevated temperatures. These thermophilic organisms produce thermostable phycobiliproteins, which have superior qualities much needed for wider adoption of these natural pigment–proteins in the food, textile, and other industries. Here we review the available literature on the thermostability of phycobilisome components from thermophilic species and discuss how a better appreciation of phycobiliproteins from extreme environments will benefit our fundamental understanding of photosynthetic adaptation and could provide a sustainable resource for several industrial processes.

In this recent work, the isolation of cyanobacterium CCC 744 from the state of Manipur, India, was focused. The isolation showed an evolutionary relationship with Anabaena sp. It was evident that 6.61% of ash was present in the biomass of isolated cyanobacteria, followed by 26.10% of carbohydrate, 38.57% of protein, 27.13% of lipid, and 1.6% of moisture. The production ability of CCC 744 was evaluated after cultivation in BG 11 medium for 30 days, and 135.42 μg/mg of C-phycocyanin (PC), 12.39 μg/mg of C-phycoerythrin (PE), 36.03 μg/mg of allophycocyanin (APC), 7.44 μg/mg of chlorophyll-a, 33.7 μg/mg of ammonia excretion, and 327.03 mg/l of exopolysaccharide (EPS) were produced. Here in this investigation, purification and characterization of released polysaccharide (RPS) and capsular polysaccharide (CPS) were also studied. Both EPSs were found negative in charge, and the major component of both EPSs was carbohydrate. The molecular weight of RPS and CPS was measured by size exclusion chromatography (SEC) and found as 46.89 and 12.64 KDa, respectively. The value of flow index for CPS and RPS was found to be 0.22 and 0.355, respectively, indicating that they are pseudoplastic fluid. A 1000 μg of CPS and RPS showed 1.32 and 1.92 times, respectively, higher antioxidant potential than 10 μg of ascorbic acid. Results also showed that 300 μg of CPS and 500 μg of CPS exhibited 1.69 and four times higher scavenging potentiality, respectively, than 10 μg of gallic acid. The amount of exopolysaccharide and phycobiliprotein production was impressive and can be exploited in the future for large-scale production.

C-phycocyanin (C-PC) is a phycobiliprotein that can be used as a natural blue dye in the food and cosmetic industries, as a biomarker or as an agent in medical treatments, depending on its purity grade. Here we described for the first time a single-step purification process of C-PC extracted from the wet biomass of Spirulina (Arthrospira) platensis LEB-52 using ion exchange chromatography with pH gradient elution. Different conditions varying the elution buffers and volumes, the loading pH and the addition of salt in the elution buffer were studied. The chromatographic condition that resulted in high recovery and purity consisted in equilibration and washing with 0.025 mol/L Tris-HCl buffer pH 6.5 and elution combining a step with 0.08 mol/L NaCl in 0.025 mol/L Tris-HCl buffer pH 6.5 and a pH gradient elution with 0.05 mol/L citrate buffer pH 6.2–3.0. This process resulted in C-PC with purities of 4.2 and 3.5 with recoveries of 32.6 and 49.5 %, respectively, in one purification step.

Photosynthesis is an ancient and important chemical reaction process. Under light conditions, plants, algae, and certain bacteria convert solar energy into chemical energy. And then, chemical energy is directly used by living cells. A special light-harvesting pigment protein, phycobiliprotein (PBP), exists in red algae, cyanobacteria (blue-green algae), and some cryptophytes to capture light energy in the water environment. Since the first discovered of PBP, scientists have conducted in-depth research on the structure, function and application of PBP. PBP is a water-soluble protein. It is formed by the covalent connection of apoprotein and phycobilin. According to the spectral characteristics, PBP can be divided into four types: Phycoerythrin (PE), phycocyanin (PC), allophycocyanin (APC) and phycoerythrocyanin (PEC). Through the coordination of four PBPs, more than 95% of the energy can be efficiently transmitted. PE is the beginning of the energy transfer of the PBP system. It is composed of three subunits α, β and γ, and the molecular weight is about 240 kD. Among them, the γ subunit has the function of connecting and stabilizing, so that PE can exist in a stable (αβ) 6γ form. PE can covalently connect chromophores such as phycoerythrobilin (PEB) and phycourobilin (PUB), and has a strong absorption efficiency for short-wavelength blue and green light. It enables red algae and cyanobacteria to efficiently capture and transfer light energy in the deep blue and green light environment. PE is a bright red fluorescent protein. When excited by a specific wavelength, PE will emit strong fluorescence. Food-grade PE can be used as a natural colorant in food, cosmetics and other fields. High-purified PE is combined with proteins such as biotin and monoclonal antibodies to make fluorescent probes for immunodetection and other technologies; PE can also be used as a new photosensitizer for photodynamic therapy of deep tissues. In addition, PE has also been proven to have anti-oxidant and anti-inflammatory biological activities, and has a certain therapeutic effect on Alzheimer’s disease, cancer, diabetes, liver and kidney toxicity and other diseases. But there is no doubt that PE has great potential in the field of biotechnology. The application of PE is closely related to its purity. China’s abundant red algae resources provide a large amount of raw materials for large-scale preparation of PE. However, there are many obstacles in the preparation of high-purified PE. The most commonly used column chromatography has the problem of expansion, while other purification processes are not mature. In view of the above problems, this review highlights an overview on the structure, function and purification process of PE. Then the applications of PE in optical and biological activities are reviewed and prospected. This article provides a reference for the high value processing and application of marine algae.

Members of the freshwater red algal order Batrachospermales are often described as shade-adapted. Nevertheless, recent ecophysiological studies have demonstrated species-level differences in acclimation to a range of irradiances. Lympha mucosa occurs in open and shaded portions of temperate streams and is abundant during summer months, suggesting it tolerates high and low irradiances. Specimens of L. mucosa were collected from open (sun-acclimated) or shaded (shade-acclimated) sites and exposed to low (

The objective of the present study was to determine the optimal incubation conditions for Gloiopeltis furcata culture. Three experiments, each lasting 30 days, were conducted to study the effects of photoperiod (6:18, 8:16, 12:12, 14:10, and 16:8 h light/dark), different wavelengths of LED light (blue, green, yellow, red, and white), and solar radiation filtered through different plastic films (blue, green, yellow, red, and white) on the growth and photosynthetic pigment content of G. furcata. The results of these experiments demonstrated that the growth rate of G. furcata was significantly higher under 14:10 and 16:8 light/dark than under 6:18 and 8:16 light/dark, while the pigment content of G. furcata was significant higher under 6:18 and 8:16 than under 14:10 and 16:8 light/dark. The growth rate of G. furcata was the lowest when the algae were exposed to blue LED and the highest under yellow LED illumination, while the phycobiliprotein content was the highest under blue LED and the lowest under yellow LED. Solar radiation filtered through different plastic films had no significant effect on the growth rate of G. furcata, but affected its pigment content. The results indicate that a photoperiod of 12 h or more of light and yellow LED are the optimal parameters for culturing of G. furcata thalli on land.

Phycobilisomes are large light-harvesting complexes attached to the stromal side of thylakoids in cyanobacteria and red algae. They can be remodeled or degraded in response to changing light and nutritional status. Both the core and the peripheral rods of phycobilisomes contain biliproteins. During biliprotein biosynthesis, open-chain tetrapyrrole chromophores are attached covalently to the apoproteins by dedicated lyases. Another set of non-bleaching (Nb) proteins has been implicated in phycobilisome degradation, among them NblA and NblB. We report in vitro experiments with lyases, biliproteins and NblA/B which imply that the situation is more complex than currently discussed: lyases can also detach the chromophores and NblA and NblB can modulate lyase-catalyzed binding and detachment of chromophores in a complex fashion. We show: (i) NblA and NblB can interfere with chromophorylation as well as chromophore detachment of phycobiliprotein, they are generally inhibitors but in some cases enhance the reaction; (ii) NblA and NblB promote dissociation of whole phycobilisomes, cores and, in particular, allophycocyanin trimers; (iii) while NblA and NblB do not interact with each other, both interact with lyases, apo- and holo-biliproteins; (iv) they promote synergistically the lyase-catalyzed chromophorylation of the β-subunit of the major rod component, CPC; and (v) they modulate lyase-catalyzed and lyase-independent chromophore transfers among biliproteins, with the core protein, ApcF, the rod protein, CpcA, and sensory biliproteins (phytochromes, cyanobacteriochromes) acting as potential traps. The results indicate that NblA/B can cooperate with lyases in remodeling the phycobilisomes to balance the metabolic requirements of acclimating their light-harvesting capacity without straining the overall metabolic economy of the cell.

R-phycoerythrin is a fluorescent red protein-pigment complex present in red algae. It belongs to the light-harvesting phycobiliprotein family with phycocyanin and allophycocyanin, which together make up the phycobilisome. The protein is most commonly used for its fluorescence properties in biochemistry. To determine the highest R-phycoerythrin yielding red algal species, a reliable quantification method is required. Calculating R-phycoerythrin yield from the crude extract’s absorption values has been the quickest and most widely used technique but at the same time, often misleading approach when impurities are present. Small phycoerythrin, which is often present in red algal suspensions, alters the absorption curve and leads to erroneous results. In the given study, we utilized an HPLC-SEC method with fluorescence and photo-diode array detectors, which is capable of separating the phycobiliproteins from interfering compounds. Also, the technique can detect and quantitate R-phycoerythrin yields reliably. A total of nine red algal species from Estonian and Japanese waters were tested, and small phycoerythrin was detected from most of the samples. For two of the tested species, the spectrophotometric quantification methods overestimated the yields by more than 200%.

Seaweeds can produce certain pigments under specific light, salinity, and nutrient conditions. These pigments have important biological activities, which have been cited in numerous published literature; thus, they have been considered of nutraceutical importance. Solieria filiformis and Gracilaria cornea (Rhodophyta) have been studied for their ability to produce pigments, polysaccharides, and other nutraceuticals with antioxidant activity. Our group currently cultivates these species under an environmentally friendly integrated multi-trophic aquaculture (IMTA) system. In the present study, the ability of these seaweeds to synthesize carotenoids and phycobiliproteins by light quality modulation in laboratory cultures was determined. The experimental design used light-emitting diodes (LEDs) for the evaluation of individual light quality effects (white, blue, green, and red) and a combination of white + blue light for the combined effect. Five replicates per treatment were implemented. Seaweeds were kept in 800-mL polyethylene culture containers with Provasoli-enriched seawater at 22 °C for 3 weeks. The cultures were irradiated between 100 and 110 μmol photons m−2 s−1 with a 12:12 light:dark cycle. Growth parameters, pigment content, C:N ratio, and antioxidant activity were determined. The growth rate increased significantly when seaweeds were subjected to the combination of white + blue light, whereas chlorophyll a synthesis was improved under the green light treatment. As for phycobiliproteins, blue and green light resulted in the highest synthesis of phycoerythrin in S. filiformis and G. cornea, respectively. The synthesis of carotenoids increased with exposure to white light in both species whereas the antioxidant activity increased with the white + blue combination in G. cornea and with white light in S. filiformis. Light quality can promote growth and synthesis of certain compounds in red macroalgae; understanding these variables would be an advantage to control their nutraceutical quality in culture.

The cyanobacterium Acaryochloris marina MBIC 11017 (A. marina 11017) possesses chlorophyll d (Chl. d) peaking at 698 nm as photosystem reaction center pigments, instead of chlorophyll a (Chl. a) peaking at 665 nm. About 95% of the total chlorophylls is Chl. d in A. marina 11017. In addition, A. marina 11017 possesses phycobilisome (PBS) supercomplex to harvest orange light and to transfer the absorbing energy to the photosystems. In this context, A. marina 11017 utilizes both far-red and orange light as the photosynthetic energy source. In the present study, we incubated A. marina 11017 cells under monochromatic orange and far-red light conditions and performed transcriptional and morphological studies by RNA-seq analysis and electron microscopy. Cellular absorption spectra, transcriptomic profiles, and microscopic observations demonstrated that PBS was highly accumulated under an orange light condition relative to a far-red light condition. Notably, transcription of one cpcBA operon encoding the phycobiliprotein of the phycocyanin was up-regulated under the orange light condition, but another operon was constitutively expressed under both conditions, indicating functional diversification of these two operons for light harvesting. Taking the other observations into consideration, we could illustrate the photoacclimation processes of A. marina 11017 in response to orange and far-red light conditions in detail.

Cyanobacteria are photosynthesizing prokaryotic microorganisms that stand out by the production of phycobiliproteins, which can be used as therapeutic agents, tools for medical diagnosis and as natural compounds for food coloring and cosmetics. Therefore, in order to purify the most relevant phycobiliproteins [phycocyanin (PC), allophycocyanin (APC) and phycoerythrin (PE)] from Anabaena variabilis and Nostoc sp., an aqueous two-phase system (ATPS) with different proportions of PEG/salt was used. The system was composed by PEG1500 and different salts, including potassium phosphate, sodium citrate and ammonium sulfate. Notably, both strains revealed high concentrations of phycobiliproteins when compared to other studies, highlighting the efficacy of the method. The highest values of the partition coefficient (K) observed in A. variabilis were obtained by 13% (w/w) PEG 14% (w/w) potassium phosphate proportion (KPC = 8.63 KAPC = 5.11 and KPE = 4,94) and for Nostoc sp., 13%PEG/14% sodium citrate proportion (KPC = 17.18, KAPC = 32,65 and KPE = 7.15).