Microalgae: A Promising Source of Bioactive Phycobiliproteins

Phycobiliproteins are photosynthetic light-harvesting pigments isolated from microalgae with fluorescent, colorimetric and biological properties, making them a potential commodity in the pharmaceutical, cosmetic and food industries. Hence, improving their metabolic yield is of great interest. In this regard, the present review aimed, first, to provide a detailed and thorough overview of the optimization of culture media elements, as well as various physical parameters, to improve the large-scale manufacturing of such bioactive molecules. The second section of the review offers systematic, deep and detailed data about the current main features of phycobiliproteins. In the ultimate section, the health and nutritional claims related to these bioactive pigments, explaining their noticeable potential for biotechnological uses in various fields, are examined.

Sustainable Production of Pigments from Cyanobacteria

Pigments are intensely coloured compounds used in many industries to colour other materials. The demand for naturally synthesised pigments is increasing and their production can be incorporated into circular bioeconomy approaches. Natural pigments are produced by bacteria, cyanobacteria, microalgae, macroalgae, plants and animals. There is a huge unexplored biodiversity of prokaryotic cyanobacteria which are microscopic phototrophic microorganisms that have the ability to capture solar energy and CO2 and use it to synthesise a diverse range of sugars, lipids, amino acids and biochemicals including pigments. This makes them attractive for the sustainable production of a wide range of high-value products including industrial chemicals, pharmaceuticals, nutraceuticals and animal-feed supplements. The advantages of cyanobacteria production platforms include comparatively high growth rates, their ability to use freshwater, seawater or brackish water and the ability to cultivate them on non-arable land. The pigments derived from cyanobacteria and microalgae include chlorophylls, carotenoids and phycobiliproteins that have useful properties for advanced technical and commercial products. Development and optimisation of strain-specific pigment-based cultivation strategies support the development of economically feasible pigment biorefinery scenarios with enhanced pigment yields, quality and price. Thus, this chapter discusses the origin, properties, strain selection, production techniques and market opportunities of cyanobacterial pigments.

A Review on a Hidden Gem: Phycoerythrin from Blue-Green Algae

Phycoerythrin (PE) is a pink/red-colored pigment found in rhodophytes, cryptophytes, and blue-green algae (cyanobacteria). The interest in PE is emerging from its role in delivering health benefits. Unfortunately, the current cyanobacterial-PE (C-PE) knowledge is still in the infant stage. It is essential to acquire a more comprehensive understanding of C-PE. This study aimed to review the C-PE structure, up and downstream processes of C-PE, application of C-PE, and strategies to enhance its stability and market value. In addition, this study also presented a strengths, weaknesses, opportunities, and threats (SWOT) analysis on C-PE. Cyanobacteria appeared to be the more promising PE producers compared to rhodophytes, cryptophytes, and macroalgae. Green/blue light is preferred to accumulate higher PE content in cyanobacteria. Currently, the prominent C-PE extraction method is repeated freezing-thawing. A combination of precipitation and chromatography approaches is proposed to obtain greater purity of C-PE. C-PE has been widely exploited in various fields, such as nutraceuticals, pharmaceuticals, therapeutics, cosmetics, biotechnology, food, and feed, owing to its bioactivities and fluorescent properties. This review provides insight into the state-of-art nature of C-PE and advances a step further in commercializing this prospective pigment.

The Effect of Colored and White Light on Growth and Phycobiliproteins, Chlorophyll and Carotenoids Content of the Marine Cyanobacteria Phormidium sp. and Cyanothece sp. in Batch Cultures

Two local marine cyanobacteria, Phormidium sp. and Cyanothece sp., were batch-cultured under 18–19.5 °C, at 40 ppt salinity, using white LED light of low (40 μmol photons/m²/s) and high (160 μmol/m²/s) intensity and, additionally, blue, green and red LED light. Yield was highest in high white light in both species (2.15 g dw/L in Phormidium, 1.47 g/L in Cyanothece), followed by green light (1.25 g/L) in Cyanothece and low white and green (1.26–1.33 g/L) in Phormidium. Green light maximized phycocyanin in Phormidium (0.45 mg/mL), while phycoerythrin was enhanced (0.17 mg/mL) by blue light and allophycocyanin by all colors (~0.80 mg/mL). All colors maximized phycocyanin in Cyanothece (~0.32 mg/mL), while phycoerythrin and allophycocyanin peaked under green light (~0.138 and 0.38 mg/mL, respectively). In Phormidium, maximization of chlorophyll-a (9.3 μg/mL) was induced by green light, while total carotenoids and b-carotene (3.05 and 0.89 μg/mL, respectively) by high white light. In Cyanothece, both white light intensities along with green maximized chlorophyll-a (~9 μg/mL) while high white light and green maximized total carotenoids (2.6–3.0 μg/mL). This study strongly indicates that these cyanobacteria can be cultured at the first stage under white light to accumulate sufficient biomass and, subsequently, under colored light for enhancing phycobiliproteins.

Biosynthesis and biotechnological interventions for commercial production of microalgal pigments: A review

Microalgae are photosynthetic eukaryotes that serve as microbial cell factories for the production of useful biochemicals, including pigments. These pigments are eco-friendly alternatives to synthetic dyes and reduce environmental and health risks. They also exhibit excellent anti-oxidative properties, making them a useful commodity in the nutrition and pharmaceutical industries. Light-harvesting pigments such as chlorophylls and phycobilins, and photoprotective carotenoids are some of the most common microalgal pigments. The increasing demand for these pigments in industrial applications has prompted a need to improve their metabolic yield in microalgal cells. So far, expensive cultivation methods and sensitivity to microbial contamination remain the main obstacles to the large-scale production of these pigments. This review highlights current issues and future prospects related to the production of microalgal pigments. The review also emphasizes the use of engineering approaches such as genetic engineering, and optimization of media components and physical parameters to increase their commercial-scale production.

Simultaneous Application of Mixotrophic Culture and Magnetic Fields as a Strategy to Improve Spirulina sp. LEB 18 Phycocyanin Synthesis

Spirulina is a filamentous microalga which is considered a promising alternative source of essential nutrients and active biomolecules. High production cost and the space required to install a photobioreactor are two of the greatest challenges in the industrial application of microalga-based products. Thus, this study aimed to improve Spirulina sp. LEB 18 biomass and phycocyanin content by combining the application of mixotrophic culture and magnetic fields (MF). Zarrouk medium was modified with 1 and 3 g/L liquid molasses and the application of 30 mT for 1·h/d was investigated. Mixotrophic culture with 1 g/L molasses showed the highest biomass concentration (1.62 g/L), carbohydrate content (25.6%), and lipid contents (8.7%) after 15 days. Although the combination of 30 mT and 1 g/L liquid molasses decreased biomass production (1.44 g/L), there was increase in protein yield (76.9%) and protein productivity (73.8 mg/L·d). The proposed method increased phycocyanin production by 145% and its purity from 0.584 in the control culture to 0.627. Data described by this study show that the combination of mixotrophic culture and MF application is a promising alternative to increase microalga protein and phycocyanin production.