Extraction, purification and characterization of phycocyanin from Oscillatoria quadripunctulata—Isolated from the rocky shores of Bet-Dwarka, Gujarat, India

Screening of symbiotic Streptomyces spp. and optimization of microalgal growth in a microalgae-actinomycetes co-culture system

Microalgal biodiesel as a substitute for fossil energy has attracted extensive attention. However, the high cost of microalgae cultivation limits the industrial production of microalgal biodiesel. The co-culture system may offer a means to increase microalgae's biomass production. In this study, Streptomyces strains were selected to construct and optimize co-culture systems with Monoraphidium sp. HDMA-11 and the algal cell biomass, lipid content, phycocyanin content, starch content, and fatty acid composition were determined. The results showed that Streptomyces nojiriensis significantly promoted Monoraphidium sp. HDMA-11 growth and a co-culture system were established. Orthogonal experiments showed that the Monoraphidium sp. HDMA-11 biomass was further increased when the initial culture pH was 7.5, the inoculation time of Streptomyces strain supernatants was 36 h, the volume ratio of microalgal actinomycetes was 1:1, and no additional acetic acid was added. Under these conditions, compared with monocultured Monoraphidium sp. HDMA-11, the cell biomass and lipid productivity of the co-culture system increased by 525.8 and 155.1%, respectively. These results suggest that S. nojiriensis supernatant potentially enhances microalgae biomass and may represent a new method to improve microalgae growth.

Commercial Potential of the Cyanobacterium Arthrospira maxima: Physiological and Biochemical Traits and the Purification of Phycocyanin

Simple Summary

Arthrospira maxima is an unbranched, filamentous cyanobacterium rich in important cellular products such as vitamins, minerals, iron, essential amino acids, essential fatty acids, and protein, which has made it one of the most important commercial photoautotrophs. To optimize the growth conditions for the production of target compounds and to ensure profitability in commercial applications, the effects of pH and temperature were investigated. A. maxima has been shown to be tolerant to a range of pH conditions and to exhibit hyper-accumulation of phycoerythrin and allophycocyanin at low temperatures. These traits may offer significant advantages for future exploitation, especially in outdoor cultivation with fluctuating pH and temperature. Our study also demonstrated a new method for the purification of phycocyanin from A. maxima by using by ultrafiltration, ion-exchange chromatography, and gel filtration, producing PC at 1.0 mg·mL⁻¹ with 97.6% purity.

Abstract

Arthrospira maxima is a natural source of fine chemicals for multiple biotechnological applications. We determined the optimal environmental conditions for A. maxima by measuring its relative growth rate (RGR), pigment yield, and photosynthetic performance under different pH and temperature conditions. RGR was highest at pH 7–9 and 30 °C. Chlorophyll a, phycocyanin, maximal quantum yield (F_v/F_m), relative maximal electron transport rate (rETR_max), and effective quantum yield (Φ_PSII) were highest at pH 7–8 and 25 °C. Interestingly, phycoerythrin and allophycocyanin content was highest at 15 °C, which may be the lowest optimum temperature reported for phycobiliprotein production in the Arthrospira species. A threestep purification of phycocyanin (PC) by ultrafiltration, ion-exchange chromatography, and gel filtration resulted in a 97.6% purity of PC.

Cyanobacterial biorefinery: Towards economic feasibility through the maximum valorization of biomass

Cyanobacteria are well known for their plethora of applications in the fields of food industry, pharmaceuticals and bioenergy. Their simple growth requirements, remarkable growth rate and the ability to produce a wide range of bio-active compounds enable them to act as an efficient biorefinery for the production of valuable metabolites. Most of the cyanobacteria based biorefineries are targeting single products and thus fails to meet the efficient valorization of biomass. On the other hand, multiple products recovering cyanobacterial biorefineries can efficiently valorize the biomass with minimum to zero waste generation. But there are plenty of bottlenecks and challenges allied with cyanobacterial biorefineries. Most of them are being associated with the production processes and downstream strategies, which are difficult to manage economically. There is a need to propose new solutions to eliminate these tailbacks so on to elevate the cyanobacterial biorefinery to be an economically feasible, minimum waste generating multiproduct biorefinery. Cost-effective approaches implemented from production to downstream processing without affecting the quality of products will be beneficial for attaining economic viability. The integrated approaches in cultivation systems as well as downstream processing, by simplifying individual processes to unit operation systems can obviously increase the economic feasibility to a certain extent. Low cost approaches for biomass production, multiparameter optimization and successive sequential retrieval of multiple value-added products according to their high to low market value from a biorefinery is possible. The nanotechnological approaches in cyanobacterial biorefineries make it one step closer to the goal. The current review gives an overview of strategies used for constructing self-sustainable- economically feasible- minimum waste generating; multiple products based cyanobacterial biorefineries by the efficient valorization of biomass. Also the possibility of uplifting new cyanobacterial strains for biorefineries is discussed.

Phycocyanin, a super functional ingredient from algae; properties, purification characterization, and applications

Phycocyanins (PCYs) are a group of luxuriant bioactive compounds found in blue-green algae with an estimated global market of about US$250 million within this decade. The multifarious markets of PCYs noted by form (e.g. powder or aqueous forms), by grade (e.g. analytical, cosmetic, or food grades), and by application (such as biomedical, diagnostics, beverages, foods, nutraceuticals and pharmaceuticals), show that the importance of PCYs cannot be undermined. In this comprehensive study, an overview on PCY, its structure, and health-promoting features are diligently discussed. Methods of purification including chromatography, ammonium sulfate precipitation and membrane filtration, as well as characterization and measurement of PCYs are described. PCYs could have many applications in food colorants, fluorescent markers, nanotechnology, nutraceutical and pharmaceutical industries. It is concluded that PCYs offer significant potentials, although more investigations regarding its purity and safety are encouraged.

Enhancement of Phycobiliprotein Accumulation in Thermotolerant Oscillatoria sp. through Media Optimization

Phycobiliproteins (PBPs) are a group of brilliant pigment proteins found in cyanobacteria and red algae; their synthesis and accumulation depend on several factors such as the type of strain employed, nutrient concentration, light intensity, light regimes, and others. This study evaluates the effect of macronutrients (citrate buffer, NaNO₃, K₂HPO₄, MgSO₄, CaCl₂, Na₂CO₃, and EDTA) and the concentration of trace metals in BG-11 media on the accumulation of PBPs in a thermotolerant strain of Oscillatoria sp. The strain was grown in BG-11 media at 28 °C with a light:dark cycle of 12:12 h at 100 μmol m^-2 s^-1 for 15 days, and the effect of nutrients was evaluated using a Plackett-Burman Design followed by optimization using a response surface methodology. Results from the concentration of trace metals show that it can be reduced up to half-strength in its initial concentration without affecting both biomass and PBPs. Results from the Plackett-Burman Design revealed that only NaNO₃, Na₂CO₃, and K₂HPO₄ show a significant increase in PBP production. Optimization employed a central Non-Factorial Response Surface Design with three levels and four factors (3⁴) using NaNO₃, Na₂CO₃, K₂HPO₄, and trace metals as variables, while the other components of BG-11 media (citrate buffer, MgSO₄, CaCl₂, and EDTA) were used in half of their initial concentration. Results from the optimization show that interaction between Na₂CO₃ and K₂HPO₄ highly increased PBPs' concentration, with values of 15.21, 3.95, and 1.89 (% w/w), respectively. These results demonstrate that identifying and adjusting the concentration of critical nutrients can increase the concentration of PBPs up to two times for phycocyanin and allophycocyanin while four times for phycoerythrin. Finally, the reduction in non-key nutrients' concentration will reduce the production costs of colorants at an industrial scale and increase the sustainability of the process.

Spirulina sp. LEB 18-extracted phycocyanin: Effects on liposomes' physicochemical parameters and correlation with antiradical/antioxidant properties

This study describes the physicochemical properties of soybean asolectin (ASO) liposomes loaded with phycocyanin (Phy) extracted from Spirulina sp. LEB 18. The effects of Phy in the liposomes' properties were investigated by Fourier transform infrared spectroscopy (FTIR), ¹H and ³¹P nuclear magnetic resonance (NMR), zeta (ζ)-potential, dynamic light scattering (DLS) and ultraviolet-visible (UV-vis) techniques. Phy restricted the motion of ASO polar and interface groups and disrupted the package arrangement of the lipid hydrophobic regions, as a likely effect of dipolar and π interactions related to its amino acid residues and pyrrole portions. These interactions were correlated to antiradical/antioxidant Phy responses obtained by 2,2-diphenyl-1-picrylhidrazil (DPPH) assay, thiobarbituric acid reactive substances (TBARS) and ferric reducing antioxidant power (FRAP) methods, and discussed to bring new chemical perspectives about Phy-loaded liposomes-related nutraceutical applications in inflammatory and viral infection processes.

Optimization of the Freezing-Thawing Method for Extracting Phycobiliproteins from Arthrospira sp

The freezing-thawing method had been reported to be the best phycobiliprotein extraction technique. However, optimum parameters of this extraction method for Arthrospira sp. (one of the major phycobiliprotein sources) still remained unclear. Hence, this study aimed to optimize the freezing-thawing parameters of phycobiliprotein extraction in Arthrospira sp. (UPMC-A0087). The optimization of the freezing-thawing method was conducted using different solvents, biomass/solvent ratios, temperatures, time intervals and freezing-thawing cycles. The extracted phycobiliproteins were quantified using a spectrophotometric assay. Double distilled water (pH 7) with a 0.50% w/v biomass/solvent ratio was the most efficient solvent in extracting high concentrations and purity of phycobiliproteins from Arthrospira sp. In addition, the combination of freezing at -80 °C (2 h) and thawing at 25 °C (24 h) appeared to be the optimum temperature and extraction time to obtain the highest amount of phycobiliproteins. A minimum of one cycle of freezing and thawing was sufficient for extracting high concentrations of phycobiliproteins. The findings from this study could reduce the cost and labor needed for extracting high quality phycobiliproteins. It also allowed the harvesting of large amounts of valuable phycobiliproteins.

Potential Therapeutic Applications of C-Phycocyanin

BACKGROUND

Cancer and other disorders such as inflammation, autoimmune diseases and diabetes are the major health problems observed all over the world. Therefore, identifying a therapeutic target molecule for the treatment of these diseases is urgently needed to benefit public health. C-Phycocyanin (C-PC) is an important light yielding pigment intermittently systematized in the cyanobacterial species along with other algal species. It has numerous applications in the field of biotechnology and drug industry and also possesses antioxidant, anticancer, antiinflammatory, enhanced immune function, including liver and kidney protection properties. The molecular mechanism of action of C-PC for its anticancer activity could be the blockage of cell cycle progression, inducing apoptosis and autophagy in cancer cells.

OBJECTIVES

The current review summarizes an update on therapeutic applications of C-PC, its mechanism of action and mainly focuses on the recent development in the field of C-PC as a drug that exhibits beneficial effects against various human diseases including cancer and inflammation.

CONCLUSION

The data from various studies suggest the therapeutic applications of C-PC such as anti-cancer activity, anti-inflammation, anti-angiogenic activity and healing capacity of certain autoimmune disorders. Mechanism of action of C-PC for its anticancer activity is the blockage of cell cycle progression, inducing apoptosis and autophagy in cancer cells. The future perspective of C-PC is to identify and define the molecular mechanism of its anti-cancer, anti-inflammatory and antioxidant activities, which would shed light on our knowledge on therapeutic applications of C-PC and may contribute significant benefits to global public health.

Ultrasound-Assisted Extraction and Assessment of Biological Activity of Phycobiliprotein-Rich Aqueous Extracts from Wild Cyanobacteria (Aphanizomenon flos-aquae)

Cyanobacteria are photosynthetic microorganisms that are considered as an important source of bioactive metabolites, among which phycobiliproteins (PBPs) are a class of water-soluble macromolecules of cyanobacteria with a wide range of applications. Massive proliferation of cyanobacteria can lead to excessive surface water blooms, of which removal, as a management measure, should be prioritized. In this study, the utilization of wild cyanobacteria biomass (Aphanizomenon flos-aquae) for extraction of phycobiliproteins is reported. Extraction of phycobiliproteins by conventional methods, such as homogenization, freeze-thaw cycles, and solid-liquid extraction, were optimized prior to ultrasound-assisted extraction. Standardization of ultrasonication for different parameters, such as ultrasonication amplitude (38, 114, and 190 μm) and ultrasonication time (1, 5.5, and 10 min), was carried out using a central composite design and response surface methodology for each of the primary techniques. A substantial increase on the individual and total phycobiliprotein yields was observed after ultrasonic treatment. The highest total PBP yield (115.37 mg/g of dry weight) was observed with samples treated with a homogenizer (30 min, 30 °C, and 1 cycle) combined with ultrasound treatment (8.7 min at 179 μm). Moreover, in vitro antioxidant capacity was observed for the obtained extracts in the Folin-Ciocalteu and ABTS^* + assays. In addition, a cytotoxic effect against C6 glioma cells was observed for A. flos-aquae PBPs. Conclusively, wild cyanobacteria could be considered as an alternative feedstock for recovery of PBPs.

Rapid Green Extractions of C-Phycocyanin from Arthrospira maxima for Functional Applications

Cyanobacteria are a rich source of bioactive compounds, mainly in the Arthospira sp., and one of the most interesting components in recent years has been C-phycocyanin (C-PC). There have been several conventional methods for their extraction, among which stand out: chemical products, freezing-thawing (FT); enzymatic, and maceration (M); which have come to be replaced by more environmentally friendly methods, such as those assisted by microwaves (MW) and high-pressure homogenization (HPH). The aim of the research was to use these two “green extraction processes” to obtain C-PC from cyanobacteria Arthrospira maxima because they improve functionality and are fast. Extractions of C-PC were studied by means of two experimental designs for MW and HPH, based on a response surface methodology (RSM) employing, firstly, a factorial design 33: power (100, 200, and 300 W), time (15, 30, and 60 s), and types of solvents (distiller water, Na-phosphate buffer and, distiller water: Na-phosphate buffer (Ph 7.0; 1:1, v/v); and secondly, two factors with different levels: Pressure (800, 1000, 1200, 1400, and 1600 bar) and, types of solvents (distilled water, Na-phosphate buffer (pH 7.0) 100 mM and, Na-phosphate buffer:water 1:1, (v/v)). Optimum C-PC content was achieved with the HPH process under Na-phosphate solvent at 1400 bar (291.9 ± 6.7 mg/g) and the MW method showed improved results using distilled water as a solvent at 100 W for 30 s (215.0 ± 5.5 mg/g). In the case of conventional methods, the freeze–thawing procedure reached better results than maceration using the buffer (225.6 ± 2.6 mg/g). This last one also did not show a significant difference between solvents (a range of 147.7–162.0 mg/g). Finally, the main advantage of using green extractions are the high C-PC yield achieved, effectively reducing both processing times, costs, and increasing the economic and functional applications of the bioactive compound.

Stepwise extraction of high-value chemicals from Arthrospira (Spirulina) and an economic feasibility study

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Phycocyanin (8.66%) was the main product from the process of the stepwise extraction.

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In addition, 3.55% TFA and 0.72% polysaccharide were coproducts from the Arthrospira residue.

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Arthrospira should contain 15% phycocyanin to ensure a positive NPV of investment.

Arthrospira (Spirulina) consists of diverse high-value chemicals, such as phycocyanin, lipids/total fatty acids (TFA), and polysaccharides, which have been used for food, cosmetic and pharmacological applications. This study compared various stepwise extraction processes for these high-value chemicals. Considering the yield and properties of extracts, the most suitable extraction order was phycocyanin, lipid/TFA and polysaccharides. The yield of the main product (food-grade phycocyanin) was 8.66% of the biomass dry weight, whereas the yields of the subsequent lipid/TFA and polysaccharide coproducts were 3.55% and 0.72%, respectively. The economic analysis showed that producing phycocyanin alone was economically feasible, but producing coproducts (lipid/TFA and polysaccharides) was not. The production cost of phycocyanin was US$ 249.70 kg⁻¹, which is an encouraging figure for large-scale production. Moreover, the phycocyanin content of Arthrospira materials utilized for extraction should not be lower than 15% of dry weight to ensure positive the net present value (NPV) of investment.

New Approach for Controlling Snail Host of Schistosoma mansoni, Biomphalaria alexandrina with Cyanobacterial Strains-Derived C-Phycocyanin

Schistosomiasis is one of the major communicable diseases of public health and socioeconomic importance in the developing world. It is a waterborne disease in which Biomphalaria alexandrina snails are known to be the intermediate molluscan host for Schistosoma mansoni: the causative agent of human intestinal schistosomiasis. Therefore, snail control is one of the cornerstones of schistosomiasis control programs. Several methods have been used to eliminate snail hosts. One of these methods is chemical molluscicides, which have undesirable effect to nontarget organisms. Consequently, the search for biologically derived molluscicides to complement the use of synthetic molluscicides is a top priority. In this concern, this study is the first to evaluate the molluscicidal potency of Cyanobacterial Phycocyanin (C-PC) as a virtually untapped source. Laboratory assessment of three freshwater Cyanobacterial strains: Anabaena oryzae SOS13, Nostoc muscorum SOS14, and Spirulina platensis SOS13-derived C-Phycocyanin as a biocontrol agent against freshwater mollusks; B. alexandrina snails were performed. Also, the safety of tested C-PC on nontarget organisms (Tilapia fish) was assessed. Results reveal that C-PC extracted from all tested Cyanobacteria strains showed a promising molluscicidal activity (the mortality rate was 100% at 100 μg/mL concentration). Out of the examined strains, A. oryzae SOS13 phycocyanin was found to be the most potent strain (LC₅₀ and LC₉₀ were 38.492 and 49.976 μg/mL, respectively). Moreover, C-PC extracts from all tested strains have been found to be safe to Tilapia fish as the survival rate was 100% at the effective molluscicidal concentrations. We can conclude that C-PC extracts are the first promising microbial biopesticides for the control of freshwater B. alexandrina snails.

Outdoor pilot-scale cultivation of Spirulina sp. LEB-18 in different geographic locations for evaluating its growth and chemical composition

This study evaluated whether outdoor cultivation of Spirulina sp. in different geographical locations affected its growth and biomass quality, with respect to the chemical composition, volatile compound and heavy metal content, and thermal stability. The positive effect of solar radiation and temperature on biomass productivity in Spirulina sp. cultivated in the northeast was directly related to its improved nutritional characteristics, which occurred with an increase in protein, phycocyanin, and polyunsaturated fatty acid (mainly γ-linolenic) content. The biomass produced in Northeast and South Brazil showed high thermal stability and had volatile compounds that could be used as biomarkers of Spirulina, and their parameters were within the limits of internationally recognized standards for food additives; hence, they have been considered safe foods. However, the growth of crops in south Brazil occurred at lower rates due to low temperatures and luminous intensities, indicative of the robustness of microalgae in relation to these parameters.

A mobile device-based imaging spectrometer for environmental monitoring by attaching a lightweight small module to a commercial digital camera

Spatially-explicit data are essential for remote sensing of ecological phenomena. Lately, recent innovations in mobile device platforms have led to an upsurge in on-site rapid detection. For instance, CMOS chips in smart phones and digital cameras serve as excellent sensors for scientific research. In this paper, a mobile device-based imaging spectrometer module (weighing about 99 g) is developed and equipped on a Single Lens Reflex camera. Utilizing this lightweight module, as well as commonly used photographic equipment, we demonstrate its utility through a series of on-site multispectral imaging, including ocean (or lake) water-color sensing and plant reflectance measurement. Based on the experiments we obtain 3D spectral image cubes, which can be further analyzed for environmental monitoring. Moreover, our system can be applied to many kinds of cameras, e.g., aerial camera and underwater camera. Therefore, any camera can be upgraded to an imaging spectrometer with the help of our miniaturized module. We believe it has the potential to become a versatile tool for on-site investigation into many applications.

Higher production of C-phycocyanin by nitrogen-free (diazotrophic) cultivation of Nostoc sp. NK and simplified extraction by dark-cold shock

Nostoc sp. NK (KCTC 12772BP) was isolated and cultivated in a BG11 medium and a nitrate-free BG11 medium (BG11₀). To enhance C-phycocyanin (C-PC) content in the cells, different fluorescent lamps (white, plant, and red) were used as light sources for complementary chromatic adaptation (CCA). The maximum biomass productivity was 0.42g/L/d and 0.32g/L/d under BG11 and BG11₀ conditions, respectively. The maximum C-PC contents were 8.4% (w/w) under white lamps, 13.6% (w/w) under plant lamps, and 18% (w/w) under BG11₀ and the red light condition. The maximum C-PC productivity was 57.4mg/L/d in BG11₀ under the red lamp condition. These results indicate that a higher C-PC content could be obtained under a diazotrophic condition and a CCA reaction. The C-PC could be released naturally from cells without any extraction processes, when Nostoc sp. NK was cultivated in the BG11₀ medium with CO₂ aeration and put in dark conditions at 5°C.

Selenium–phycocyanin from selenium-enriched cultures of Nostoc sp. isolated from rice field prevents human kidney cells from paraquat-induced damage

Herein we demonstrate that Se-containing phycocyanin (Se–PC) purified from Se-enriched cultures of Nostoc sp. could reverse paraquat (PQ)-induced DNA cell apoptosis through inhibition of superoxide overproduction in human kidney cells.

Detection of Free Thiols and Fluorescence Response of Phycoerythrin Chromophore after Ultraviolet-B Radiation Stress

The chemistry of thiol-chromophore linkage plays a central role in the nature of fluorescence of phycoerythrin (PE). Interaction of thiol and chromophore is crucial for the energy transfer, redox signal and inhibition of oxidative damage. In the present investigation the effects of ultraviolet-B radiation on an emission fluorescence intensity and wavelength shift in PE due to interaction between thiol and chromophore by remarkable strategy of detection technique was studied. Purification of PE was done by using a gel permeation and ion exchange chromatography that yielded a quite high purity index (6.40) in a monomeric (αβ) form. UV-B radiation accelerated the quenching efficiency (24.9 ± 1.52%) by reducing fluorescence emission intensity of thiol linked chromophore after 240 min of UV-B exposure. However, after blocking of transiently released free thiol by N-ethylmaleimide, quenching efficiency was increased (36.8 ± 2.80%) with marked emission wavelength shift towards shorter wavelengths up to 562 nm as compared to 575 nm in control. Emission fluorescence of free thiol was at maximum after 240 min that was detected specifically by monobromobimane (mBrB) molecular probe. The association/dissociation of bilin chromophore was analyzed by SDS- and Native-PAGE that also indicated a complete reduction in emission fluorescence. Our work clearly shows an early detection of free thiols and relative interaction with chromophore after UV-B radiation which might play a significant role in structural and functional integrity of terminal PE.

Recent advances in production, purification and applications of phycobiliproteins

An obligatory sunlight requirement for photosynthesis has exposed cyanobacteria to different quantity and quality of light. Cyanobacteria can exhibit efficient photosynthesis over broad region (450 to 650 nm) of solar spectrum with the help of brilliantly coloured pigment proteins called phycobiliproteins (PBPs). Besides light-harvesting, PBPs are found to involve in several life sustaining phenomena including photoprotection in cyanobacteria. The unique spectral features (like strong absorbance and fluorescence), proteineous nature and, some imperative properties like hepato-protective, anti-oxidants, anti-inflammatory and anti-aging activity of PBPs enable their use in food, cosmetics, pharmaceutical and biomedical industries. PBPs have been also noted to show beneficial effect in therapeutics of some disease like Alzheimer and cancer. Such large range of applications increases the demand of PBPs in commodity market. Therefore, the large-scale and coast effective production of PBPs is the real need of time. To fulfil this need, many researchers have been working to find the potential producer of PBPs for the production and purification of PBPs. Results of these efforts have caused the inventions of some novel techniques like mixotrophic and heterotrophic strategies for production and aqueous two phase separation for purification purpose. Overall, the present review summarises the recent findings and identifies gaps in the field of production, purification and applications of this biological and economically important proteins.

Crystal structure analysis of phycocyanin from chromatically adapted Phormidium rubidum A09DM

Structural and sequence analyses of Phormidium phycocyanin revealed three co-evolving residues that determine the conformation of a phycocyanobilin chromophore believed to play role in alternate pathways for intra and inter-rod energy transfer.

Crystal Structure of Allophycocyanin from Marine Cyanobacterium Phormidium sp. A09DM

Isolated phycobilisome (PBS) sub-assemblies have been widely subjected to X-ray crystallography analysis to obtain greater insights into the structure-function relationship of this light harvesting complex. Allophycocyanin (APC) is the phycobiliprotein always found in the PBS core complex. Phycocyanobilin (PCB) chromophores, covalently bound to conserved Cys residues of α- and β- subunits of APC, are responsible for solar energy absorption from phycocyanin and for transfer to photosynthetic apparatus. In the known APC structures, heterodimers of α- and β- subunits (known as αβ monomers) assemble as trimer or hexamer. We here for the first time report the crystal structure of APC isolated from a marine cyanobacterium (Phormidium sp. A09DM). The crystal structure has been refined against all the observed data to the resolution of 2.51 Å to R_work (R_free) of 0.158 (0.229) with good stereochemistry of the atomic model. The Phormidium protein exists as a trimer of αβ monomers in solution and in crystal lattice. The overall tertiary structures of α- and β- subunits, and trimeric quaternary fold of the Phormidium protein resemble the other known APC structures. Also, configuration and conformation of the two covalently bound PCB chromophores in the marine APC are same as those observed in fresh water cyanobacteria and marine red algae. More hydrophobic residues, however, constitute the environment of the chromophore bound to α-subunit of the Phormidium protein, owing mainly to amino acid substitutions in the marine protein.

Single step aqueous two-phase extraction for downstream processing of C-phycocyanin from Spirulina platensis

C-phycocyanin, a natural food colorant, is gaining importance worldwide due to its several medical and pharmaceutical applications. In the present study, aqueous two-phase extraction was shown to be an attractive alternative for the downstream processing of C-phycocyanin from Spirulina platensis. By employing differential partitioning, C-phycocyanin selectively partitioned to the polymer rich (top) phase in concentrated form and contaminant proteins to the salt rich (bottom) phase. This resulted in an increase in the product purity (without losing much of the yield) in a single step without the need of multiple processing steps. Effect of process parameters such as molecular weight, tie line length, phase volume ratio, concentration of phase components on the partitioning behavior of C-phycocyanin was studied. The results were explained based on relative free volume of the phase systems. C-phycocyanin with a purity of 4.32 and yield of about 79 % was obtained at the standardized conditions.