Stabilising phycocyanin by anionic micelles

Mechanism of Enhancing Chlorophyll Photostability through Light-Induced Chlorophyll/Phycocyanin Aggregation

Chlorophyll (Chl) is the most abundant pigment in photosynthetic plants, but it is prone to degradation during processing and storage, limiting its usage in the food industry. This study developed a technique for increasing Chl photostability by light-induced Chl/phycocyanin (PC) triple synergistic aggregation. Under continuous illumination settings, the results revealed that the Chl retention increased to 406% compared to the control. A model of Chl/PC complexes was constructed using multiligand molecular docking, and the aggregation mechanism was investigated by quantum chemistry, which demonstrated that PC could provide an ideal central hydrophobic cavity for Chl aggregates and thus further enhance the aggregation of Chl on the basis of Chl/PC complexes. The core driver of the improved photostability of Chl is photoexcitation-induced Chl aggregates. This study enriches our understanding of the interaction mechanism between PC and Chl, and we hope that this study can provide broader ideas for the development of natural pigment products.

Carboxylated chitosan improved the stability of phycocyanin under acidified conditions

Phycocyanin, a natural blue colorant, derived from Spirulina platensis, is now widely used in the food industry. However, its main drawbacks are loss of color and denature of structure in an acidic environment. In this study, carboxylated chitosan (0.1 %-1 % w/v) was chosen as an additive in acid-denatured phycocyanin for preserving phycocyanin's blue color and natural structure. Zeta-potential and particle size revealed that the carboxylated chitosan with high negative charge adsorbed on phycocyanin and provided stronger electrostatic repulsion to overcome the protein aggregation. Ultraviolet-visible absorption spectrum and fluorescence spectroscopy showed that the carboxylated chitosan recovered the microenvironment of tetrapyrrole chromophores and β-subunits, which led the secondary structure changed and the trimers depolymerized into the monomers changed by the acidic environment. Furthermore, Fourier transform infrared spectroscopy revealed highly negatively charged carboxylated chitosan with the groups (NH₂, COOH and OH) could restored the microenvironment of tetrapyrrole chromophores and β-subunits of phycocyanin, and interact with phycocyanin through hydrogen bonding, NH bonding, ionic bonding and van der Waals, which led to a change in secondary structure and depolymerization of trimers into monomers. Our study demonstrated the carboxylated chitosan played a beneficial role in recovering the structure of acid-denatured phycocyanin and its blue color.

A review of recent strategies to improve the physical stability of phycocyanin

There is an increasing demand for more healthy and sustainable diets, which led to an interest in replacing synthetic colors with natural plant-based ones. Phycocyanin, which is commonly extracted from Spirulina platensis, has been explored as a natural blue pigment for application in the food industry. It is also used as a nutraceutical in food, cosmetic, and pharmaceutical products because of its potentially beneficial biological properties, such as radical scavenging, immune modulating, and lipid peroxidase activities. The biggest challenges to the widespread application of phycocyanin for this purpose are its high sensitivity to chemical degradation when exposed to heat, light, acids, high pressure, heavy metal cations, and denaturants. Consequently, it is of considerable importance to improve its chemical stability, which requires a thorough knowledge of the relationship between the structure, environment, and chemical reactivity of phycocyanin. To increase the application of this natural pigment and nutraceutical within foods and other products, the structure, biological activities, and factors affecting its stability are reviewed, as well as strategies that have been developed to improve its stability. The information contained in this article is intended to stimulate further studies on the development of effective strategies to improve phycocyanin stability and performance.

Phycobiliproteins, the pigment-protein complex form of natural food colorants and bioactive ingredients

Currently, the use of synthetic pigments in foods is restricted since synthetic pigments are proven and suspected to be harmful to human health. Phycobiliproteins (PBPs), existed in phycobilisomes (PBSs) of algae, are a kind of pigment-proteins with intense color. The specific color of PBPs (red and blue) is given by the water-soluble open-chained tetrapyrrole chromophore (phycobilin) that covalently attaches to the apo-protein via thioether linkages to cysteine residues. According to the spectral characteristics of PBPs, they can be categorized as phycoerythrins (PEs), phycocyanins (PCs), allophycocyanins (APCs), and phycoerythrocyanins (PECs). PBPs can be used as natural food colorants, fluorescent substances, and bioactive ingredients in food applications owing to their color characteristics and physiological activities. This paper mainly summarizes the extraction and purification methods of the PBPs and reviews their characteristics and applications. Moreover, the use of several strategies such as additives, microencapsulation, electrospray, and cross-linking to improve the stability and bioavailability of PBPs as well as the future outlooks of PBPs as natural colorants in food commercialization are elucidated.

Improving the Thermal and Oxidative Stability of Food-Grade Phycocyanin from Arthrospira platensis by Addition of Saccharides and Sugar Alcohols

The water-soluble pigment protein phycocyanin (C-PC) from cyanobacteria Arthrospira sp. is an excellent natural food colorant and nutritional supplement with a brilliant blue color. However, C-PC is highly unstable, especially at high temperatures and when exposed to oxidative stress. The lack of simple and economical methods for improving the stability of C-PC greatly limits the application of this functional protein in the food industry. This study investigated the effect of adding saccharides (glucose, mannose, galactose, and maltose) and sugar alcohols (mannitol and maltitol) on the stability of food-grade C-PC extracted from Arthrospira platensis; the relevant reaction kinetics were also analyzed. The results revealed that glucose, mannose, mannitol, galactose, and maltose could effectively improve the thermal stability of C-PC. This improvement was positively correlated with the concentration of the additives and decreased sharply when the temperature exceeded 60 °C. Furthermore, the results also revealed the instability of C-PC when subjected to oxidative stress and the effectiveness of glucose, mannose, mannitol, and maltose in preventing the oxidative degradation of C-PC. In general, this study demonstrates that glucose, mannose, mannitol, and maltose are promising compounds for promoting the thermal and oxidative stability of C-PC, providing an economical and effective method for C-PC preservation.

Optimization of Phycobiliprotein Solubilization from a Thermotolerant Oscillatoria sp

The present study evaluated the effect of multiple variables (drying time, drying temperature, biomass/solvent ratio, glass beads/biomass ratio, extraction time, and extraction speed) in the solubilization of three different phycobiliproteins (C-PC, APC, and PE) from a thermotolerant Oscillatoria sp. The strain was grown in BG11 media (28 °C, light: dark cycle of 12:12 h at 100 µmol·m−2·s−1, 20 days) and the experiments were conducted according to a two-level randomized factorial design with six center points (38 runs). Results show that biomass/solvent ratio, glass beads/biomass ratio, and extraction time, are the most significant variables in the extraction of all three proteins, whereas the glass beads/biomass ratio and extraction time significantly affect their purity. The optimized conditions allow a statistical increase in the concentration of C-PC, APC, and PE extracted from the biomass; however, the purity was lower in comparison with the expected value. The latter occurs due to a larger biomass/solvent ratio and longer extraction times, which enhanced the solubility of other hydrophilic metabolites (proteins and carbohydrates, etc.).

Load phycocyanin to achieve in vivo imaging of casein-porous starch microgels induced by ultra-high-pressure homogenization

Traditional bioactive substances are often limited in practical application due to their poor stability and low solubility. Therefore, it is imperative to develop biocompatible high loading microgel carriers. In this study, a novel type of casein-porous starch microgel was prepared under ultra-high-pressure homogenization, by using porous starch with the honeycomb three-dimensional network porous structure. Molecular interaction force analysis and thermodynamic analysis showed that electrostatic interaction played a major role in the formation of microgels. Circular dichroism and Fourier transform infrared spectroscopy showed that homogenization and pH were the main factors, which affected the formation and structural stability of microgels. Compared with casein-glutinous rice starch microgels, the encapsulation efficiency and loading capacity of phycocyanin in casein-porous starch microgels were increased by 77.27% and 135.10%, respectively. Thus, casein-porous starch microgels could not only achieve a sustained release effect, but also effectively transport phycocyanin to the gastrointestinal tract of zebrafish, while achieving good fluorescence imaging in vivo. Ultimately, the prepared casein-porous starch microgels could enrich the nanocarriers material, and contribute to the research of safe and effective fluorescent imaging materials.

Physicochemical degradation of phycocyanin and means to improve its stability: A short review

The cyanobacterium Arthrospira platensis, spirulina, is a source of pigments such as phycobiliprotein and phycocyanin. Phycocyanin is used in the food, cosmetics, and pharmaceutical industries because of its antioxidant, anti-inflammatory, and anticancer properties. The different steps involved in extraction and purification of this protein can alter the final properties. In this review, the stability of phycocyanin (pH, temperature, and light) is discussed, considering the physicochemical parameters of kinetic modeling. The optimal working pH range for phycocyanin is between 5.5 and 6.0 and it remains stable up to 45 °C; however, exposure to relatively high temperatures or acidic pH decreases its half-life and increases the degradation kinetic constant. Phycobiliproteins are sensitive to light; preservatives such as mono- and di-saccharides, citric acid, or sodium chloride appear to be effective stabilizing agents. Encapsulation within nano- or micro-structured materials such as nanofibers, microparticles, or nanoparticles, can also preserve or enhance its stability.

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Phycocyanin is in great demand for industrial application.

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Phycocyanin is sensitive to pH, temperature, and light.

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Optimal stability occurs between pH 5.5–6.0 and at temperatures <45 °C in the dark.

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The use of preservatives or its encapsulation with polymers enhances its stability.

The formation of phycocyanin-EGCG complex for improving the color protection stability exposing to light

Phycocyanin (PC) is a natural pigment-protein complex in food dye applications. In this study, a phycocyanin-epigallocatechin gallate (EGCG) complex (PE) was prepared and the effects of EGCG on the structure and color stability of PC were evaluated. The fluorescence results showed that the binding number n was 62.1 ± 3.41 (EGCG/PC) and the binding constant K was 4.39 (±0.2) × 10⁵ M^-1, indicating a weak-binding interaction. Fourier transform-infrared analysis showed that EGCG caused structural changes in PC by partially uncoiling α-helix and increasing β-sheet content. The EGCG induced a PC association at a reaction molar ratio above 40:1 (EGCG/PC). Moreover, EGCG protected phycocyanobilin against color fading, making PE more stable relative to PC under 8-days storage in light. This study provides a novel scheme to stabilize PC by forming a complex with polyphenols, which will facilitate the PC application as a natural blue pigment in food.

Enhanced Microencapsulation of C-Phycocyanin from Arthrospira by Freeze-Drying with Different Wall Materials

RESEARCH BACKGROUND

C-phycocyanin (C-PC), a water-soluble blue pigment, was extracted from microalgae Arthrospira sp. C-PC could be a good substitute for synthetic pigments with high antioxidant activity. However, C-PC is unstable due to sensitivity to temperature, light, pH and oxygen; therefore, applications of C-PC in food and other products are limited. Microencapsulation of C-PC using freeze-drying is a solution to this problem and is considered a suitable method for drying the heat-sensitive pigment.

EXPERIMENTAL APPROACH

C-phycocyanin was extracted from Arthrospira platensis. C-PC microcapsules were modified by freeze-drying, with maltodextrin and gum Arabic used as microencapsulation wall materials at different fractions from 0 to 100%. The physical properties including moisture content and water activity, solubility, hygroscopicity, bulk density, colour appearance, particle morphology and size distribution of the produced powders were evaluated. Thermal stability and antioxidant activity of freeze-dried microencapsulated C-PC powders were also assessed.

RESULTS AND CONCLUSIONS

Freeze-dried microencapsulated C-PC powders with maltodextrin and gum Arabic as wall materials gave high encapsulation efficiency of around 99%. At higher gum Arabic mass fraction, moisture content decreased and water activity improved. Maltodextrin gave higher solubility of C-PC powders whereas gum Arabic led to a similar colour of C-PC to those without microencapsulation. Freeze-dried microencapsulated C-PC powders were composed of different sized microparticles regardless of the combination of wall materials with amorphous glassy shapes. Thermal stability of encapsulated C-PC increased and also showed high antioxidant properties.

NOVELTY AND SCIENTIFIC CONTRIBUTION

This study demonstrates that the freeze-dried microencapsulated C-PC powders have pigment stability with antioxidant properties and are resistant to high temperatures. Therefore, they may have a potential for the development of microencapsulated C-PC as a functional ingredient with improved colour and bioactive properties. Such a product can be applied in food, cosmetic, biotechnology and nutraceutical industries.

Extraction Methods for Obtaining Natural Blue Colorants

Background:

Blue is a color not often present in food. Even so, it is especially attractive to children. Today, most blue coloring agents used by the food industry are synthetic. With increasing health issues concern by the scientific community and the general population, there is a trend to look for natural alternatives to most synthetic products. There only exist few natural blue colorants, which are presented in a literature survey, along with the methods currently used for their recovery from natural sources. The best extraction methods and process parameters for the extraction of blue anthocyanins, iridoids and phycocyanin are discussed.

Methods:

A literature survey was conducted to detect the main sources of blue colorants found in nature. The focus was on the extraction methods used to recover such molecules, with the objective of finding efficient and environmentally safe techniques for application at industrial level, and, thus, allowing the production of natural blue colorants at scale high enough for food industry consumption.

Results:

The main natural blue colorants found in literature are anthocyanins, phycocyanin, and genipin. While anthocyanins can be recovered from a variety of plants, the source of phycocyanin are algae, and genipin can be obtained specifically from Gardenia jasminoides Ellis and Genipa americana L. Several extraction techniques have been applied to recover blue colorants from such sources, from classical methods using organic solvents, to more sophisticated technologies as ultrasoundassisted extraction, supercritical fluid extraction, pressurized liquid extraction, high-pressure extraction, and enzyme-assisted extraction.

Conclusion:

There is great potential for anthocyanins, phycocyanin and genipin use as natural food additives with health benefits, besides imparting color. However, the technologies for the colorants recovery and application are not mature enough. Therefore, this area is still developing, and it is necessary to evaluate the economic feasibility of the proposed extraction processes, along with the safety and acceptance of colored food using these additives.

Phycobiliproteins from extreme environments and their potential applications

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.