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

Deep Eutectic Solvents based green approach for bioactive molecules recovery from Spirulina

Spirulina is a unicellular microalga, characterized by blue/green color, that has received significant attention for its interesting nutritional composition. Phenolic compounds and phycocyanin (PC) are responsible for the many biological activities of Spirulina. Spirulina phenolic compounds are usually extracted using organic solvents, while PC is extracted with water or phosphate buffer solution, obtaining an extract characterized by low stability and low purity. Deep Eutectic Solvents (DESs) are green solvents, widely applied for bioactive molecules extraction, composed by two or more molecules which act as hydrogen bond acceptor or hydrogen bond donor to create an eutectic mixture. A Natural Deep Eutectic Solvent (NADES), is a DES composed only by natural compounds. This work aimed to optimize a green extraction procedure based on NADES to obtain an extract rich in phenolic compounds and PC from Spirulina. The application of NADESs as extraction solvents is an important strategy for recovering phenolic compounds and to increase and stabilize the protein PC. The optimized extraction procedure involved to use a betaine-glucose NADES under the following conditions: matrix-to-solvent ratio of 1:20 (w/w), temperature of 50 °C and one hour as extraction time. The developed extraction procedure guaranteed to recover a phenolic compounds and PC quantity of 11.77 ± 1.23 mg GAE (gallic acid equivalents) and 27.56 ± 2.46 g per g of Spirulina powder respectively. PC in the NADES extract degraded more slowly than in an aqueous extract. The extract phenolic compounds profile was determined through high performance liquid chromatography coupled with mass spectrometry analysis.

Impact of pH and protein/polysaccharide ratio on phycocyanin-okra polysaccharides complex

Phycocyanin is a natural blue pigment that tends to denature and lose its color in acidic solutions. In response to this problem, the complexes of phycocyanin (PC) with okra polysaccharides (OP) were prepared by ultrasonic processing at different pH conditions, and the molecular interactions of the complexes were characterized. The results showed that there were significant differences in the color, functional groups, and surface morphology of the complexes formed at different pH conditions. By colorimetry and particle size tester, it was demonstrated that the complex solution showed a steady blue color at pH 3.4. The highest fluorescence intensity (1.55 × 107 a.u.) and the significant red-shift of the complexes were observed at 0.4 % m/v polysaccharides addition. Infrared spectroscopy test further demonstrated that OP induced the formation of higher-order trimers of PC, which kept the color stable. Molecular dynamics simulations showed that the binding energy of PC/OP complex was -42.21 ± 2.61 kcal/mol, indicating that the binding affinity was very strong. Overall, this study suggests that this complex stabilizes the structure of PC, which in turn exerts a biological effect and will facilitate the use of PC as an artificial color substitute in food or beverage applications.

Direct detection of phycocyanin in sediments by hyperspectral imaging

Cyanobacteria are ubiquitous aquatic organisms with a remarkable evolutionary history reaching as far as 1.9 Ga. They play a vital role in ecosystems yet also raise concerns due to their association with harmful algal blooms. Understanding the historical patterns and drivers behind these blooms is crucial for effective ecosystem management. Lake-sediment cores are valuable natural environmental archives, recording the histories of such blooms. Among others, phycocyanin, a pigment specific to cyanobacteria, emerges as a promising biomarker for reconstructing past cyanobacterial bloom events. However, due to the physicochemical properties of phycocyanin, there is no validated method available to extract and measure this pigment from complex sediment matrix. This study explores the applicability of hyperspectral imaging (HSI), a non-destructive technique, as a novel approach for high resolution in-situ detection and quantification of phycocyanin in lake sediments. Our experiments show that phycocyanin can be detected by HSI with an absorption trough at 620 nm (relative absorption band depth, RABD620). We established a semi-quantitative calibration of the spectral index RABD620 by conducting spiking experiments with phycocyanin standard (known phycocyanin mass) on organic-rich and mineral-rich sediments of varying water contents. We also assessed potential interference from chlorophyll a, another photosynthetic pigment, ensuring the reliability of hyperspectral phycocyanin measurements. Our findings demonstrate a significant correlation (R2 ranging from 0.37 to 0.997) between the RABD620 index and associated phycocyanin amounts in organic-rich and minerogenic sediments. This indicates the potential of the spectral index to directly measure in-situ biomarker concentrations on split sediment cores. Although confounding factors such as water and chlorophyll a content can influence the spectral signal, this method offers a rapid and non-destructive approach for studying historical cyanobacterial blooms in sedimentary records. This opens promising grounds for various applications, including ecosystem-health assessment and environmental change monitoring.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10933-024-00350-y.

The blue palette of life: A comprehensive review of natural bluish colorants with potential commercial applications

Considering the growing interest for safer, environmentally friendly and healthier products, the search for natural colorants to replace their synthetic has been raised. This is particularly challenging for the rare and usually unstable bluish coloring substances. This comprehensive review describes several bluish pigments which can be obtained from natural sources (plants and mostly microorganisms), covering less known molecules to well established compounds (although no focus is given for anthocyanins). Key information about each compound, including sources, extraction procedures, properties, and potential applications, are presented. Despite many studies on these molecules, toxicological and stability studies are still lacking for many of them. Therefore, this text also discusses the regulatory requirements for approving new coloring substances. Given the increasing robustness of scientific data supporting the biological activities attributed to many of these pigments, it is possible to envisage that some of them may be commercially available for industrial applications in different fields, not only in traditional food or cosmetic uses but in pharmaceutical formulations as well.

Phycocyanin-Loaded Alginate-Based Hydrogel Synthesis and Characterization

Phycocyanin was extracted from Spirulina platensis using conventional extraction (CE), direct ultrasonic-assisted extraction (direct UAE), indirect ultrasonic-assisted extraction (indirect UAE), and microwave-assisted extraction (MAE) methods at different temperatures, extraction intervals, stirring rate, and power intensities while maintaining the same algae to solvent ratio (1:15 w/v). The optimization of the extraction parameters indicated that the direct UAE yielded the highest phycocyanin concentration (29.31 ± 0.33 mg/mL) and antioxidant activity (23.6 ± 0.56 mg TE/g algae), while MAE achieved the highest purity (Rp = 0.5 ± 0.002). Based on the RP value, phycocyanin extract obtained by MAE (1:15 w/v algae to solvent ratio, 40 min, 40 °C, and 900 rpm) was selected as active compound in an alginate-based hydrogel formulation designed as potential wound dressings. Phycocyanin extracts and loaded hydrogels were characterized by FT-IR analysis. SEM analysis confirmed a porous structure for both blank and phycocyanin loaded hydrogels, while the mechanical properties remained approximately unchanged in the presence of phycocyanin. Phycocyanin release kinetics was investigated at two pH values using Zero-order, First-order, Higuchi, and Korsmeyer-Peppas kinetics models. The Higuchi model best fitted the experimental results. The R2 value at higher pH was nearly 1, indicating a superior fit compared with lower pH values.

Trends in extracting protein from microalgae Spirulina platensis, using innovative extraction techniques: mechanisms, potentials, and limitations

Microalgal, species are recognized for their high protein content, positioning them as a promising source of this macronutrient. Spirulina platensis, in particular, is noteworthy for its rich protein levels (70 g/100 g dw), which are higher than those of meat and legumes. Incorporating this microalgae into food can provide various benefits to human health due to its diverse chemical composition, encompassing high amount of protein and elevated levels of minerals, phenolics, essential fatty acids, and pigments. Conventional techniques employed for protein extraction from S. platensis have several drawbacks, prompting the exploration of innovative extraction techniques (IETs) to overcome these limitations. Recent advancements in extraction methods include ultrasound-assisted extraction, microwave-assisted extraction, high-pressure-assisted extraction, supercritical fluid extraction, pulse-electric field assisted extraction, ionic liquids assisted extraction, and pressurized liquid extraction. These IETs have demonstrated efficiency in enhancing protein yield of high quality while maximizing biomass utilization. This comprehensive review delves into the mechanisms, applications, and drawbacks associated with implementing IETs in protein extraction from S. platensis. Notably, these innovative methods offer advantages such as increased extractability, minimized protein denaturation, reduced solvent consumption, and lower energy consumption. However, safety considerations and the synergistic effects of combined extraction methods warrant further exploration and investigation of their underlying mechanisms.

Phycocyanin from microalgae: A comprehensive review covering microalgal culture, phycocyanin sources and stability

As food safety continues to gain prominence, phycocyanin (PC) is increasingly favored by consumers as a natural blue pigment, which is extracted from microalgae and serves the dual function of promoting health and providing coloration. Spirulina-derived PC demonstrates exceptional stability within temperature ranges below 45 °C and under pH conditions between 5.5 and 6.0. However, its application is limited in scenarios involving high-temperature processing due to its sensitivity to heat and light. This comprehensive review provides insights into the efficient production of PC from microalgae, covers the metabolic engineering of microalgae to increase PC yields and discusses various strategies for enhancing its stability in food applications. In addition to the most widely used Spirulina, some red algae and Thermosynechococcus can serve as good source of PC. The genetic and metabolic manipulation of microalgae strains has shown promise in increasing PC yield and improving its quality. Delivery systems including nanoparticles, hydrogels, emulsions, and microcapsules offer a promising solution to protect and extend the shelf life of PC in food products, ensuring its vibrant color and health-promoting properties are preserved. This review highlights the importance of metabolic engineering, multi-omics applications, and innovative delivery systems in unlocking the full potential of this natural blue pigment in the realm of food applications, provides a complete overview of the entire process from production to commercialization of PC, including the extraction and purification.

Optimizing Phycocyanin Extraction from Cyanobacterial Biomass: A Comparative Study of Freeze-Thaw Cycling with Various Solvents

Cyanobacterial phycocyanin pigment is widely utilized for its properties in various industries, including food, cosmetics, and pharmaceuticals. Despite its potential, challenges exist, such as extraction methods impacting yield, stability, and purity. This study investigates the impact of the number of freeze-thaw (FT) cycles on the extraction of phycocyanin from the wet biomass of four cyanobacteria species (Arthrospira platensis, Chlorogloeopsis fritschii, Phormidium sp., and Synechocystis sp.), along with the impact of five extraction solutions (Tris-HCl buffer, phosphate buffer, CaCl2, deionized water, and tap water) at various pH values. Synechocystis sp. exhibited the highest phycocyanin content among the studied species. For A. platensis, Tris-HCl buffer yielded maximum phycocyanin concentration from the first FT cycle, while phosphate buffer provided satisfactory results from the second cycle. Similarly, Tris-HCl buffer showed promising results for C. fritschii (68.5% of the maximum from the first cycle), with the highest concentration (~12% w/w) achieved during the seventh cycle, using phosphate buffer. Phormidium sp. yielded the maximum pigment concentration from the first cycle using tap water. Among species-specific optimal extraction solutions, Tris-HCl buffer demonstrated sufficient extraction efficacy for all species, from the first cycle. This study represents an initial step toward establishing a universal extraction method for phycocyanin from diverse cyanobacteria species.

Saline extraction assisted by ultrasound: a method to obtain purified phycocyanin

The influence of ultrasound intensity and saline solution concentration (NH4Cl and CaCl2) on phycocyanin extraction from Arthrospira platensis was evaluated. The intensity had a significant effect on phycocyanin content and purity, while the saline solution concentration only had an effect on purity. The optimum extraction condition was obtained at 41% of intensity and 8.5 g.L-1 of CaCl2 solution. In this condition, ultrasound promoted cell disruption efficiently, increasing the extraction yield. The combination of ultrasound with CaCl2 solution reduced the co-extraction of chlorophylls and other proteins, providing more purified extracts. The freezing and thawing method was compared to the best condition obtained, and it showed no significant difference for phycocyanin content but better results for purity. Overall, ultrasound treatment may be considered a promising technology to obtain phycocyanin by the food industry without additional purification techniques due to the reduced extraction time, less use of energy, and easy scale-up.

Structural, extraction and safety aspects of novel alternative proteins from different sources

With rapid population growth and continued environmental degradation, it is no longer sustainable to rely on conventional proteins to meet human requirements. This has prompted the search for novel alternative protein sources of greater sustainability. Currently, proteins of non-conventional origin have been developed, with such alternative protein sources including plants, insects, algae, and even bacteria and fungi. Most of these protein sources have a high protein content, along with a balanced amino acid composition, and are regarded as healthy and nutritious sources of protein. While these novel alternative proteins have excellent nutritional, research on their structure are still at a preliminary stage, particularly so for insects, algae, bacteria, and fungi. Therefore, this review provides a comprehensive overview of promising novel alternative proteins developed in recent years with a focus on their nutrition, sustainability, classification, and structure. In addition, methods of extraction and potential safety factors for these proteins are summarized.

Isolation and identification of Methylobacterium komagatae and its application in textile industries

A light pink-coloured, rod-shaped, gram-negative bacterium isolated from an unproductive crude oil production area was considered as a sample for this study. The 16S rRNA gene sequence identified the isolate as Methylobacterium komagatae. Comparing the standard colour measurement values set by the International Commission on Illumination (CIE) method confirms the colourant produced by the biomass of this microorganism as a 'light pink' colouration. The energy-dispersive X-ray spectroscopy and High-Resolution Mass Spectroscopy process help in the structural elucidation of the sample. It indicates the presence of magnesium (Mg) as a central metal atom in the bacterial colourant, i.e. 'bacteriochlorophyll' (BChl) (MgC55H74N4O). The recovered bacterial colourant was applied to cotton fabric and cotton yarns to dye and examine their fastness quality. The result shows the cotton fabrics retained colourant in normal washing while it got reduced after detergent-based washing. Therefore, its fastness quality must be improved to equalise with current colourants.

Reversible disassembly-reassembly of C-phycocyanin in pressurization-depressurization cycles of high hydrostatic pressure

Hydrostatic pressure can reversibly modulate protein-protein and protein-chromophore interactions of C-phycocyanin (C-PC) from Spirulina platensis. Small-angle X-ray scattering combined with UV-Vis spectrophotometry and protein modeling was used to explore the color and structural changes of C-PC under high pressure conditions at different pH levels. It was revealed that pressures up to 350 MPa were enough to fully disassemble C-PC from trimers to monomers at pH 7.0, or from monomers to detached subunits at pH 9.0. These disassemblies were accompanied by protein unfolding that caused these high-pressure induced structures to be more extended. These changes were reversible following depressurization. The trimer-to-monomer transition proceeded through a collection of previously unrecognized, L-shaped intermediates resembling C-PC dimers. Additionally, pressurized C-PC showed decayed Q-band absorption and fortified Soret-band absorption. This was evidence that the folded tetrapyrroles, which had folded at ambient pressure, formed semicyclic unfolded conformations at a high pressure. Upon depressurization, the peak intensity and shift all recovered stepwise, showing pressure can precisely manipulate C-PC's structure as well as its color. Overall, a protein-chromophore regulatory theory of C-PC was unveiled. The pressure-tunability could be harnessed to modify and stabilize C-PC's structure and photochemical properties for designing new delivery and optical materials.

Partitioning Recovery of Natural Pigments from Spirulina platensis

In the last few decades, the recovery of high-added value compounds with high food potential using microalgae as feedstock has been one of the main challenges for both research and industry. This study provides a simple, affordable, and cost-saving approach for the selective recovery of C-phycocyanin (C-PC), chlorophyll a and carotenoids from Spirulina platensis biomass by using biocompatible and industrially approved solvents (such as CaCl2 and ethanol). The concentration and yield of each pigment in the liquid extract have been spectrophotometrically detected, whereas the decolorized protein-rich biomass has been analyzed by CIELab parameters. The most concentrated (566.4 μg/mL) and food-grade C-PC extract (purity index 0.7) was obtained by applying a biomass/solvent ratio (1:10) for the first round of extraction (20 min), followed by a second round at 1:5 using CaCl2 1.5% (w/v) aqueous solution. Additionally, the same trial enabled the production of the brightest decolorized protein-rich biomass (L* = 46.2), characterized by a yellow-orange tonality (h° values = 81.3°).

Photocatalytic degradation of reactive dyes using natural photo-smart pigment-A novel approach for waste water re-usability

The present study is aimed at an efficient photocatalytic degradation of industrially important reactive dyes using phycocyanin extract as a photocatalyst. The percentage of dye degradation was evidenced by a UV-visible spectrophotometer and FT-IR analysis. The degraded water was checked for its complete degradation by varying pH from 3 to 12. Furthermore, the degraded water was also analyzed for water quality parameters and was found to meet industrial wastewater standards. The calculated irrigation parameters like magnesium hazard ratio, soluble sodium percentage, and Kelly's ratio of degraded water were within the permissible limits, which enables its reusability in irrigation, aquaculture, as industrial coolants, and domestic applications. The calculated correlation matrix shows that the metal influences various macro-, micro-, and non-essential elements. These results suggest that the non-essential element lead can be effectively reduced by increasing all the other micronutrients and macronutrients under study except sodium metal.

Efficient extraction of phycobiliproteins from dry biomass of Spirulina platensis using sodium chloride as extraction enhancer

An efficient strategy for phycobiliprotein extraction from Spirulina platensis dry biomass has been developed by using NaCl as an enhancer. Different sodium ion and chloride ion salts were screened, and NaCl was selected as the most appropriate solvent for phycobiliprotein extraction. The extraction parameters with NaCl were optimized using response surface methodology. Under optimal operating conditions, a phycobiliprotein extraction rate of 74.8 % and a phycocyanin extraction yield of 102.4 mg/g with a purity of 74.0 % were achieved. Adding NaCl resulted in smaller fragments and destroyed the cell integrity of S. platensis, facilitating phycobiliprotein exudation. The secondary structure and antioxidant activity of phycobiliproteins were not affected by NaCl extraction. The stability of the phycobiliproteins was improved by adding NaCl. This study provides a potential method for phycobiliprotein extraction with high efficiency and good quality using an inexpensive extraction enhancer.

Exploring the Benefits of Phycocyanin: From Spirulina Cultivation to Its Widespread Applications

Large-scale production of microalgae and their bioactive compounds has steadily increased in response to global demand for natural compounds. Spirulina, in particular, has been used due to its high nutritional value, especially its high protein content. Promising biological functions have been associated with Spirulina extracts, mainly related to its high value added blue pigment, phycocyanin. Phycocyanin is used in several industries such as food, cosmetics, and pharmaceuticals, which increases its market value. Due to the worldwide interest and the need to replace synthetic compounds with natural ones, efforts have been made to optimize large-scale production processes and maintain phycocyanin stability, which is a highly unstable protein. The aim of this review is to update the scientific knowledge on phycocyanin applications and to describe the reported production, extraction, and purification methods, including the main physical and chemical parameters that may affect the purity, recovery, and stability of phycocyanin. By implementing different techniques such as complete cell disruption, extraction at temperatures below 45 °C and a pH of 5.5-6.0, purification through ammonium sulfate, and filtration and chromatography, both the purity and stability of phycocyanin have been significantly improved. Moreover, the use of saccharides, crosslinkers, or natural polymers as preservatives has contributed to the increased market value of phycocyanin.

Comparative Study of the Efficiency of Additives in the Extraction of Phycocyanin-C from Arthrospira maxima Using Ultrasonication

Several phycocyanin extraction methods have been proposed, however, most of them present economical or productive barriers. One of the most promising methods that has been suggested is ultrasonication. We have analyzed here the effect of operational conditions and additives on the extraction and purity of phycocyanin from Arthrospira maxima. We followed three experimental designs to determine the best combination of buffered pH solutions, additives, fresh and lyophilized biomass. We have found that additives such as citric acid and/or disaccharides could be beneficial to the extraction process. We concluded that the biomass-solvent ratio is a determining factor to obtain high extraction and purity ratios with short ultrasonication times.

The increasing role of structural proteomics in cyanobacteria

Cyanobacteria, also known as blue–green algae, are ubiquitous organisms on the planet. They contain tremendous protein machineries that are of interest to the biotechnology industry and beyond. Recently, the number of annotated cyanobacterial genomes has expanded, enabling structural studies on known gene-coded proteins to accelerate. This review focuses on the advances in mass spectrometry (MS) that have enabled structural proteomics studies to be performed on the proteins and protein complexes within cyanobacteria. The review also showcases examples whereby MS has revealed critical mechanistic information behind how these remarkable machines within cyanobacteria function.

Improved pH stability, heat stability, and functionality of phycocyanin after PEGylation

Phycocyanin (PC), a spirulina-derived protein-chromophore complex, suffers from poor techno-functional properties and is highly susceptible to aggregation and color changes upon heating and pH fluctuations. We tackled these issues by modifying PC via PEGylation. Electrophoresis and Fourier transform infrared spectroscopy proved successful conjugation of methoxy PEG (mPEG) chains on PC after PEGylation. Circular dichroism indicated highly ordered folding states adopted by PEGylated PC, which we attributed to the mPEG chains on the protein surface that sterically stabilized the protein structure. Consequently, the mPEG-PC conjugates exhibited high blue color intensity and improved thermodynamic stability. Further, benefit from an electrostatic shielding effect of mPEG chains, surface charges of PEGylated PC were neutralized over pH 2-9 and the blue hue of PC was stabilized against pH variations. Additionally, the flexible and hydrophilic mPEG polymers on the PC surface promoted protein-protein and protein-water interactions. PEGylated PC thus gained increased protein solubility, techno-functionality (emulsifying, foaming, and gelling performance), and antioxidant activities, when compared to unmodified PC. Heat-induced gels formed by mPEG-PC conjugates exhibited increased stiffness, higher water retention, and weak gel-type rheological properties. After PEGylation, the improved functional properties, bioactivity, and color stability against heat and pH fluctuations will facilitate food and pharmaceutical applications of PC.

Influence of Geographical Location of Spirulina (Arthrospira platensis) on the Recovery of Bioactive Compounds Assisted by Pulsed Electric Fields

Spirulina (Arthrospira platensis) has been consumed by humans since ancient times. It is rich in high added-value compounds such as chlorophylls, carotenoids and polyphenols. Pulsed electric fields (PEF) is an innovative non-thermal technique that improves the extraction of bioactive compounds from diverse sources. PEF pre-treatment (3 kV/cm, 100 kJ/kg) combined with supplementary extraction with binary solvents at different times was evaluated to obtain the optimal conditions for extraction. In addition, the results obtained were compared with conventional treatment (without PEF pre-treatment and constant shaking) and different strains of Spirulina from diverse geographical locations. The optimal extraction conditions for recovering the bioactive compounds were obtained after applying PEF treatment combined with the binary mixture EtOH/H2O for 180 min. The recovery of total phenolic content (TPC) (19.76 ± 0.50 mg/g DM (dry matter) and carotenoids (0.50 ± 0.01 mg/g DM) was more efficient in the Spirulina from Spain. On the other hand, there was a higher recovery of chlorophylls in the Spirulina from China. The highest extraction of total antioxidant compounds was in Spirulina from Costa Rica. These results show that PEF, solvents and the condition of growing affect the extraction of antioxidant bioactive compounds from Spirulina. The combination of PEF and EtOH/H2O is a promising technology due to its environmental sustainability.

Green Extraction Process of Food Grade C-phycocyanin: Biological Effects and Metabolic Study in Mice

This study aimed to evaluate different parameters in the green process of organic Spirulina biomass (SB) C-phycocyanin (C-PC) extraction to understand the impact on weight and oral glucose tolerance of C-PC extract in Swiss mice fed with a high-fat diet (HFD). The proximate composition and antioxidant activity were analyzed in Spirulina by-products: SB, C-PC, and Remaining biomass (RB). The protein content on a dry basis was 52.05% in SB and 61.16% in RB and 118.97 μg/g in C-PC. The antioxidant activity was equal for SB and C-PC but higher than RB. However, RB can be considered a promising ingredient, promoting the sustainable use of the whole SB. Swiss mice were distributed in five groups: control diet (CD), HFD, HFD plus Spirulina biomass (HFDS), HFD plus C-PC (HFDC), and HFD plus remaining biomass (HFDR). HFDS increased the delta weight of the animals and showed glucose intolerance compared to the CD and HFDC groups. The results demonstrated that the supplementation of 500 mg/kg of body weight of SB in the HFDS group did not show antiobesogenic potential with an HFD, but it is essential to conduct further studies to bring other interesting responses regarding C-PC biological in vivo effects.

Factorial Optimization of Ultrasound-Assisted Extraction of Phycocyanin from Synechocystis salina: Towards a Biorefinery Approach

PC is a bioactive and colorant compound widely sought in the food, nutraceutical and cosmetic industries, and one of the most important pigments produced by Synechocystis salina. However, the general extraction process is usually time-consuming and expensive, with low extraction yields—thus compromising a feasible and sustainable bioprocess. Hence, new extraction technologies (e.g., ultrasound assisted-extraction or UAE) emerged in the latest years may serve as a key step to make the overall bioprocess more competitive. Therefore, this study aimed at optimizing the yields of phycocyanin (PC) rich-extracts of S. salina by resorting to UAE; in attempts to explore this process in a more economically feasible way; valorization of the remaining cyanobacterial biomass, via extraction of other bioactive pigments and antioxidants, was tackled within a biorefinery perspective. A two-stage extraction (using ethanol and water) was thus performed (because it favors PC extraction); other bioactive pigments, including chlorophyll a (chl a), carotenoids, and other phycobiliproteins (PBPs), but also antioxidant (AOX) capacity and extraction yields were also evaluated for their optimum UAE yields. A factorial design based on Box–Behnken model was developed; and the influence of such extraction parameters as biomass to solvent ratio (B/S ratio = 1.5–8.5 mg·mL⁻¹), duty cycle (DT = 40–100%), and percentage of amplitude (A = 40–100%) were evaluated. The model predicted higher PC yields with high B/S ratio = 6 mg·mL⁻¹, lower DT = 80% and an A = 100%. Classical extraction was compared with UAE under the optimum conditions found; the latter improved PC yields by 12.5% and 47.8%, when compared to freeze-thawing extraction, and bead beater homogenization-based extraction, respectively. UAE successive extractions allowed to valorize other important bioactive compounds than PC, by reusing biomass, supporting a favorable contribution to the economic feasibility of the S. salina-based process towards a biorefinery approach.

Phycocyanin: A Natural Antioxidant to Combat Free Radicals

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Various research showed that antioxidants can effectively overcome the damage caused by free radicals to human health. Therefore, antioxidants are identified as one of the main directions in the development of health care and cosmetics products due to high demand in the market. This review mainly focuses on the phycocyanin, a type of natural antioxidant mainly found in cyanobacteria. This mini review summarizes the phycocyanin sources and numerous extraction methods of phycocyanin along with the analytical methods and determine its ability to suppress free radicals. Phycocyanin has been proven to play an important role in scavenging free radicals and enhancing the body’s antioxidant capacity. However, there is a lack of long-term randomized clinical trial results that can be used as evidence in showing the benefits of phycocyanin. The existing phycocyanin extraction methods using solvents, ultrasonic-assisted, freeze-thaw, etc. can extract high-quality phycocyanin efficiently and quickly. Scientists are also trying to incorporate advanced technologies, such as "Industry 4.0" to optimize and enhance the industrial production of phycocyanin. Lastly, this review also describes the difficulties faced during the phycocyanin production or extraction process and financial obstacles in order to achieve the popularization of phycocyanin.

Effect of Different Extraction Methods on Physicochemical Characteristics and Antioxidant Activity of C-Phycocyanin from Dry Biomass of Arthrospira platensis

The effect of four different extraction methods on physicochemical characteristics and functionalities of chloro-phycocyanin (CP) was investigated. Swelling (S-CP), freezing and thawing (4FT-CP), ultrasonication with freezing and thawing (4FT+U-CP), and the high-pressure cell disruption (HPCD-CP) process affected CP differently, thus resulting in different levels of solubility, DPPH scavenging activity, ABTS scavenging activity, and reducing power. Among the four CPs, HPCD-CP had the highest CP content (15.3%), purity (1.66 ± 0.16), and ∆E value but the lowest ∆b value. The ζ potential of HPCD-CP (−38.8 mV) was the highest, but the average particle size of 4FT+U-CP (719.1 nm) was the highest. UV-Vis absorption spectra and fluorescence spectra illustrated that high-pressure cell disruption-assisted extraction had more profound impacts on the microenvironment of tetrapyrrole chromophores, the environment of aromatic amino acids, and the phycocyanobilin of CP. Furthermore, HPCD-CP and 4FT-CP showed higher solubility and antioxidant activities than S-CP, especially 4FT+U-CP. The results obtained in this study demonstrate that HPCD technology could obtain a food-grade C-phycocyanin product with higher CP concentration, purity, solubility, and antioxidant activity.

Tuning C-Phycocyanin Photoactivity via pH-Mediated Assembly-Disassembly

Environment-triggered protein conformational changes have garnered wide interest in both fundamental research, for deciphering in vivo acclimatory responses, and practical applications, for designing stimuli-responsive probes. Here, we propose a protein-chromophore regulatory mechanism that allows for manipulation of C-phycocyanin (C-PC) from Spirulina platensis by environmental pH and UV irradiation. Using small-angle X-ray scattering, a pH-mediated C-PC assembly-disassembly pathway, from monomers to nonamers, was unraveled. Such flexible protein matrices impart tunability to the embedded tetrapyrroles, whose photochemical behaviors were found to be modulated by protein assembly states. UV irradiation on C-PC triggers pH-dependent singlet oxygen (¹O₂) generation and conformational changes. Intermolecular photo-crosslinking occurs at pH 5.0 via dityrosine species, which bridges solution-based C-PC oligomers into unprecedented dodecamers and 24-mers. These supramolecular assemblies impart C-PC at pH 5.0, which significantly enhanced ¹O₂ yield, fluorescence, and photostability relative to those at other pH values, a finding that makes C-PC appealing for tumor-targeted photodynamic therapy.

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.

Food Matrices Affect the Peptides Produced during the Digestion of Arthrospira platensis-Based Functional Aliments

Arthrospira platensis (Spirulina) has been credited with multiple beneficial effects, many of which are attributed to bioactive peptides produced during the gastrointestinal digestion of this micro-alga. Many Spirulina-based nutraceuticals have been produced, and numerous functional foods enriched with Spirulina are available on the market. These are subjected to checks aimed at verifying the amount of algae actually present, but few studies relating to the bioavailability of the bioactive compounds in these products have been carried out. However, such investigations could be very important to elucidate the possible critical effects exerted by food matrices on protein digestion and bioactive peptide production. Here, in order to assess the suitability of Spirulina-enriched foods as a source of potentially bioactive peptides, a simulated digestion protocol was used in combination with mass spectrometry quantitative analysis to analyze functionalized pasta and sorbets. In the case of the pasta enriched with Spirulina, the production of peptides was quite similar to that of the Spirulina powder. On the other hand, the type of fruit present in the food matrix influenced the digestion of Spirulina inside the sorbets. In particular, the high concentration of protease inhibitors in kiwifruit drastically reduced the production of peptides from Spirulina in kiwi sorbet.

Assessment of Phycocyanin Extraction from Cyanidium caldarium by Spark Discharges, Compared to Freeze-Thaw Cycles, Sonication, and Pulsed Electric Fields

Phycocyanin is a blue colored pigment, synthesized by several species of cyanobacteria and red algae. Besides the application as a food-colorant, the pigmented protein is of high interest as a pharmaceutically and nutritionally valuable compound. Since cyanobacteria-derived phycocyanin is thermolabile, red algae that are adapted to high temperatures are an interesting source for phycocyanin extraction. Still, the extraction of high quality phycocyanin from red algae is challenging due to the strong and rigid cell wall. Since standard techniques show low yields, alternative methods are needed. Recently, spark discharges have been shown to gently disintegrate microalgae and thereby enable the efficient extraction of susceptible proteins. In this study, the applicability of spark discharges for phycocyanin extraction from the red alga Cyanidium caldarium was investigated. The efficiency of 30 min spark discharges was compared with standard treatment protocols, such as three times repeated freeze-thaw cycles, sonication, and pulsed electric fields. Input energy for all physical methods were kept constant at 11,880 J to ensure comparability. The obtained extracts were evaluated by photometric and fluorescent spectroscopy. Highest extraction yields were achieved with sonication (53 mg/g dry weight (dw)) and disintegration by spark discharges (4 mg/g dw) while neither freeze-thawing nor pulsed electric field disintegration proved effective. The protein analysis via LC-MS of the former two extracts revealed a comparable composition of phycobiliproteins. Despite the lower total concentration of phycocyanin after application of spark discharges, the purity in the raw extract was higher in comparison to the extract attained by sonication.

Phycocyanin from Spirulina: A review of extraction methods and stability

Phycocyanin (C-PC) application by the industry is still limited due to extraction methods drawbacks and to the low stability of these compounds after the extraction process. To overcome such limitations, alternative extraction methodologies have been evaluated, and stabilizing agents have been used under different conditions in the past years. Therefore, the aim of this review was to bring the state of the art of C-PC extraction methods, including main parameters that affect the extraction process and cell disruption mechanisms, as well as the physical and chemical parameters that may influence C-PC stability. Stabilizing agents have been used to avoid C-PC content degradation during storage and food processing. A critical analysis of the extraction methods indicated that pulsed electric field (PEF) is a promising technology for C-PC extraction since the extracts present relative high C-PC concentration and purity. Other methods either result in low purity extracts or are time demanding. Regarding stabilizing agents, natural polymers and sugars are potential compounds to be used in food formulations to avoid color and antioxidant activity losses.

Mechanical Cell Disruption Technologies for the Extraction of Dyes and Pigments from Microorganisms: A Review

The production of pigments using single cell microorganisms is gaining traction as a sustainable alternative to conventional syntheses, which rely, in no negligible proportions, on petrochemicals. In addition to depending on petroleum, these syntheses involved the use of toxic organic solvents, which may be inadequately disposed of across a range of industries, thus compounding the deleterious effects of fossil fuel exploitation. Literature suggests that notable research efforts in the area of sustainable pigment production using single cell microorganisms are focused on the production of pigments coveted for their interesting qualities, which transcend their mere capacity to dye various fabrics both natural and synthetic. As interest in sustainable pigment biosynthesis grows, the need to devise effective and efficient cell disruption processes becomes more pressing given that the viability of pigment biosynthesis is not only dependent on microorganisms’ yield in terms of production, but also on researchers’ ability to recover them. This review chiefly reports findings as to mechanical cell disruption methods, used individually or in various combinations, and their aptitude to recover biosynthetic pigments.