Microalgae-Derived Pigments: A 10-Year Bibliometric Review and Industry and Market Trend Analysis

Microalgae-based sunscreens as green and sustainable cosmetic products

Recently, microalgal biotechnology has attained great acceptance among various researchers and industries for the green and sustainable production of different bioactive compounds. They provide multiple metabolites and molecules, making them an ideal candidate for cosmetic formulators and cosmeceutical companies. Nevertheless, numerous microalgae strains have never been studied for their pharmaceutical, nutritional and cosmeceutical purposes. Even less, only some have been cultivated on a large scale for bioactive compound production. Here, we have studied the cosmetic and cosmeceutical potentials of different microalgal strains for sunscreen as adjuvants and boosters in a green, carbon-neutral and sustainable platform. Other bioactive compounds were exploited, and the available products in the market and the published patents were also reviewed. From our review, it will be possible to combine the fundamental and practical aspects of microalgal biotechnology toward a greener and more sustainable future for the cosmetic/cosmeceutical areas of the photoprotection scenario.

Harnessing nature's palette: Exploring photosynthetic pigments for sustainable biotechnology

Photosynthetic microorganisms such as cyanobacteria, microalgae, and anoxygenic phototrophic bacteria (APB) have emerged as sustainable and economic biotechnology platforms due to their ability to transform energy from light into chemicals through photosynthesis. The light is absorbed by photosynthetic pigment-protein antenna complexes which are composed of pigments such as bacteriochlorophylls (BChl) and carotenoids in APB, and chlorophylls (Chl), phycobiliproteins (PBP), and carotenoids in cyanobacteria and microalgae. These photosynthetic pigments are essential in the physiology of photosynthetic microorganisms and offer significant health benefits due to their potent antioxidant activity, with properties that include anticancer, antiaging, antiproliferative, anti-inflammatory, and neuroprotective effects. This review first provides an overview of current advances in photosynthetic pigment synthesis and the latest strategies to increase pigment content in cyanobacteria, microalgae, and APB. It then delves into the pigment production process, covering biosynthetic pathways, critical environmental parameters, and extraction methods. Finally, the potential marketability of photosynthetic pigments together with current limitations are discussed.

Is it possible to shape the microalgal biomass composition with operational parameters for target compound accumulation?

Microalgae, as photosynthetic microorganisms, offer a sustainable source of proteins, lipids, carbohydrates, pigments, vitamins, and antioxidants. Leveraging their advantages, such as fast growth, CO2 fixation, cultivation without arable land, and wastewater utilisation, microalgae can produce a diverse range of compounds. The extracted products find applications in bioenergy, animal feed, pharmaceuticals, nutraceuticals, cosmetics, and food industries. The selection of microalgal species is crucial, and their biochemical composition varies during growth phases influenced by environmental factors like light, salinity, temperature, and nutrients. Manipulating growth conditions shapes biomass composition, optimising the production of target compounds. This review synthesises research from 2019 onwards, focusing on stress induction and two-stage cultivation in microalgal strategies. This review takes a broader approach, addressing the effects of various operating conditions on a range of biochemical compounds. It explores the impact of operational parameters (light, nutrient availability, salinity, temperature) on biomass composition, elucidating microalgal mechanisms. Challenges include species-specific responses, maintaining stable conditions, and scale-up complexities. A two-stage approach balances biomass productivity and compound yield. Overcoming challenges involves improving upstream and downstream processes, developing sophisticated monitoring systems, and conducting further modelling work. Future efforts should concentrate on strain engineering and refined monitoring, facilitating real-time adjustments for optimal compound accumulation. Moreover, conducting large-scale experiments is essential to evaluate the feasibility and sustainability of the process through techno-economic analysis and life cycle assessments.

Characterization of microalgal β-carotene and astaxanthin: exploring their health-promoting properties under the effect of salinity and light intensity

Microalgae are promising sources of valuable carotenoids like β-carotene and astaxanthin with numerous health benefits. This review summarizes recent studies on producing these carotenoids in microalgae under different salinity and light-intensity conditions, which are key factors influencing their biosynthesis. The carotenoid biosynthesis pathways in microalgae, involving the methylerythritol phosphate pathway in chloroplasts, are described in detail. The effects of high salinity and light stress on stimulating astaxanthin accumulation in species like Haematococcus pluvialis and Chromochloris zofingiensis and their synergistic impact are discussed. Similarly, the review covers how high light and salinity induce β-carotene production in Dunaliella salina and other microalgae. The diverse health-promoting properties of astaxanthin and β-carotene, such as their antioxidant, antiinflammatory, and anticancer activities, are highlighted. Strategies to improve carotenoid yields in microalgae through environmental stresses, two-stage cultivation, genetic engineering, and metabolic engineering approaches are evaluated. Overall, this review highlights advancements in β-carotene and astaxanthin production reporting the different microalgal capability to produce carotenoids under different stress level like 31.5% increase in β-carotene accumulation in Dunaliella salina and astaxanthin productivity reaching 18.1 mg/L/day in Haematococcus lacustris. It also explores novel biotechnological strategies, including CRISPR-Cas9, for enhancing carotenoid yield.

Unveiling astaxanthin: biotechnological advances, delivery systems and versatile applications in nutraceuticals and cosmetics

Astaxanthin (ASX), "king of carotenoids", is a xanthophyll carotenoid that is characterized by a distinct reddish-orange hue, procured from diverse sources including plants, microalgae, fungi, yeast, and lichens. It exhibits potent antioxidant and anti-ageing properties and has been demonstrated to mitigate ultraviolet-induced cellular and DNA damage, enhance immune system function, and improve cardiovascular diseases. Despite its broad utilization across nutraceutical, cosmetic, aquaculture, and pharmaceutical sectors, the large-scale production and application of ASX are constrained by the limited availability of natural sources, low production yields and stringent production requirements. This review provides a comprehensive analysis of ASX applications, emphasizing its dual roles in cosmetic and nutraceutical fields. It integrates insights into the qualitative differences of ASX from various natural sources and assesses biosynthetic pathways across organisms. Advanced biotechnological strategies for industrial-scale production are explored alongside innovative delivery systems, such as emulsions, films, microcapsules, nanoliposomes, and nanoparticles, designed to enhance ASX's bioavailability and functional efficacy. By unifying perspectives on its nutraceutical and cosmetic applications, this review highlights the challenges and advancements in formulation and commercialization. Prospective research directions for optimizing ASX's production and applications are also discussed, providing a roadmap for its future development.

Light-dependent variations in fatty acid profiles and gene expression in Antarctic microalgal cultures

Photosynthetic eukaryotic microalgae are key primary producers in the Antarctic sea ice environment. Anticipated changes in sea ice thickness and snow load due to climate change may cause substantial shifts in available light to these ice-associated organisms. This study used a laboratory-based experiment to investigate how light levels, simulating different sea ice and snow thicknesses, affect fatty acid (FA) composition in two ice associated microalgae species, the pennate diatom Nitzschia cf. biundulata and the dinoflagellate Polarella glacialis. FA profiling and transcriptomic analyses were used to compare the impact of three light levels: High (baseline culturing conditions 90 ± 1 μmol photons m-2 s-1), mid (10 ± 1 μmol photons m-2 s-1); and low (1.5 ± 1 μmol photons m-2 s-1) on each isolate. Both microalgal isolates had altered growth rates and shifts in FA composition under different light conditions. Nitzschia cf. biundulata exhibited significant changes in specific saturated and monounsaturated FAs, with a notable increase in energy storage-related FAs under conditions emulating thinner ice or reduced snow cover. Polarella glacialis significantly increased production of polyunsaturated FAs (PUFAs) in mid light conditions, particularly octadecapentaenoic acid (C18:5N-3), indicating enhanced membrane fluidity and synthesis of longer-chain PUFAs. Notably, C18:5N-3 has been identified as an ichthyotoxic molecule, with fish mortalities associated with other high producing marine taxa. High light levels caused down regulation of photosynthetic genes in N. cf. biundulata isolates and up-regulation in P. glacialis isolates. This and the FA composition changes show the variability of acclimation strategies for different taxonomic groups, providing insights into the responses of microalgae to light stress. This variability could impact polar food webs under climate change, particularly through changes in macronutrient availability to higher trophic levels due to species specific acclimation responses. Further research on the broader microalgal community is needed to clarify the extent of these effects.

Advance on the effects of algal carotenoids on inflammatory signaling pathways

The development of inflammation has an indispensable importance in the self-protection of the human body. However, over-inflammation may damage human health, and inflammatory pathways and inflammasomes have a significant impact on the onset of inflammation. Therefore, how to constrain the development of inflammation through inflammatory pathways or inflammasomes becomes a hot research issue. Carotenoids are a natural pigment and an active substance in algae, with anti-inflammatory and antioxidant effects. Many studies have shown that carotenoids have inhibitory effects on the inflammatory pathways and inflammasomes. In this review, we discussed the mechanism of carotenoids targeting those important inflammatory pathways and their effects on common inflammasome NLRP3 and inflammation-related diseases from the perspective of several inflammatory pathways, including p38 MAPK, IL-6/JAK/STAT3, and PI3K, with a focus on the targets and targeting effects of carotenoids on different inflammatory signaling pathways, and at last proposed possible anti-inflammatory targets.

Arthrospira maxima and biosynthesized zinc oxide nanoparticles as antibacterials against carbapenem-resistant Klebsiella pneumoniae and Acinetobacter baumannii: a review article

Carbapenem resistance among bacteria, especially Klebsiella pneumoniae and Acinetobacter baumannii, constitutes a dreadful threat to public health all over the world that requires developing new medications urgently. Carbapenem resistance emerges as a serious problem as this class is used as a last-line option to clear the multidrug-resistant bacteria. Arthrospira maxima (Spirulina) is a well-known cyanobacterium used as a food supplement as it is rich in protein, essential minerals and vitamins and previous studies showed it may have some antimicrobial activity against different organisms. Biosynthesized (green) zinc oxide nanoparticles have been investigated by several researchers as antibacterials because of their safety in health. In this article, previous studies were analyzed to get to a conclusion about their activity as antibacterials.

Spirulina-An Invaluable Source of Macro- and Micronutrients with Broad Biological Activity and Application Potential

With population growth expected in the near future and the planet's limited resources, alternative food sources are already being looked for. In this context, spirulina is called the food of the future due to its rich nutritional composition. This blue-green alga is primarily a valuable source of protein (55-70%) containing all essential amino acids. In its composition, it also contains unsaturated fatty acids, minerals, vitamins, and pigments, including the valuable protein-pigment complex-phycocyanin. Due to its high content of complete protein and minerals such as iron and calcium, it is an excellent addition to diets, especially those of vegans and vegetarians. Despite several limitations to the use of spirulina, including its distinctive marine flavour, low consumer awareness, or relatively high price, scientists are attempting to enrich many food products with the microalga. This is supported not only by the improved nutritional composition of the fortified product but also by spirulina's impact on sustainable food production. Therefore, this review aims to create consumer attention by presenting spirulina as a valuable and sustainable food source with health-promoting potential and great future significance.

Research progress in microalgae nutrients: emerging extraction and purification technologies, digestive behavior, and potential effects on human gut

Microalgae contain a diverse range of high-value compounds that can be utilized directly or fractionated to obtain components with even greater value-added potential. With the use of microalgae for food and medical purposes, there is a growing interest in their digestive properties and impact on human gut health. The extraction, separation, and purification of these components are key processes in the industrial application of microalgae. Innovative technologies used to extract and purify microalgal high-added-value compounds are key for their efficient utilization and evaluation. This review's comprehensive literature review was performed to highlight the main high-added-value microalgal components. The technologies for obtaining bioactive compounds from microalgae are being developed rapidly, various innovative, efficient, green separation and purification technologies are emerging, thus helping in the scaling-up and subsequent commercialization of microalgae products. Finally, the digestive behavior of microalgae nutrients and their health effects on the human gut microbiota were discussed. Microalgal nutrients exhibit favorable digestive properties and certain components have been shown to benefit gut microbes. The reality that must be faced is that multiple processes are still required for microalgae raw materials to final usable products, involving energy, time consumption and loss of ingredients, which still face challenges.

Retargeting of heterologous enzymes results in improved β-carotene synthesis in Saccharomyces cerevisiae

AIMS

Carotenoids are a class of hydrophobic substances that are important as food and feed colorants and as antioxidants. The pathway for β-carotene synthesis has been expressed in various yeast species, albeit with rather low yields and titers. The inefficient conversion of phytoene to lycopene is often regarded as a bottleneck in the pathway. In this study, we aimed at the improvement of β-carotene production in Saccharomyces cerevisiae by specifically engineering the enzymatic reactions producing and converting phytoene.

METHODS AND RESULTS

We show that phytoene is stored in intracellular lipid droplets, whereas the enzyme responsible for its conversion, phytoene dehydrogenase, CrtI, is located at the endoplasmic reticulum, like the bifunctional enzyme CrtYB that catalyses the reaction before and after CrtI. To improve the accessibility of phytoene for CrtI and to delay its storage in lipid droplets, we tested the relocation of CrtI and CrtYB to mitochondria. However, only the retargeting of CrtYB resulted in an improvement of the β-carotene content, whereas the mitochondrial variant of CrtI was not functional. Surprisingly, a cytosolic variant of this enzyme, which we obtained through the elimination of its carboxy-terminal membrane anchor, caused an increase in β-carotene accumulation. Overexpression of this CrtI variant in an optimized medium resulted in a strain with a β-carotene content of 79 mg g-1 cell dry weight, corresponding to a 76-fold improvement over the starting strain.

CONCLUSIONS

The retargeting of heterologously expressed pathway enzymes improves β-carotene production in S. cerevisiae, implicating extensive inter-organellar transport phenomena of carotenoid precursors. In addition, strong overexpression of carotenoid biosynthetic enzymes and the optimization of cultivation conditions are required for high contents.

Preventing biofouling in microalgal photobioreactors

Photobioreactors (PBRs) are used to grow the light-requiring microalgae in diverse commercial processes. Often, they are operated as continuous culture over months period. However, with time, biofouling layer develops on the inner surfaces of their walls. The fouling layer formation deteriorates the PBR performance as foulants reduce light penetration in it. Light is essential for photosynthetic cultures, and a deterioration in lighting adversely impacts algae growth and biomass productivity. Fouling requires a frequent shutdown to clean the PBR and add to the environmental impact of the operation by generating many wastewaters contaminated with the cleaning chemicals. Antibiofouling coatings could be used to modify the surfaces of existing and future PBRs. Therefore, transparent and non-toxic fouling-release coatings, produced using hydrogel technology, could transform the existing PBRs into efficient and enduring microalgae culture systems, requiring only the application of the coating to the inner walls, without additional investments in new PBRs.

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.

Genetic Engineering and Innovative Cultivation Strategies for Enhancing the Lutein Production in Microalgae

Carotenoids, with their diverse biological activities and potential pharmaceutical applications, have garnered significant attention as essential nutraceuticals. Microalgae, as natural producers of these bioactive compounds, offer a promising avenue for sustainable and cost-effective carotenoid production. Despite the ability to cultivate microalgae for its high-value carotenoids with health benefits, only astaxanthin and β-carotene are produced on a commercial scale by Haematococcus pluvialis and Dunaliella salina, respectively. This review explores recent advancements in genetic engineering and cultivation strategies to enhance the production of lutein by microalgae. Techniques such as random mutagenesis, genetic engineering, including CRISPR technology and multi-omics approaches, are discussed in detail for their impact on improving lutein production. Innovative cultivation strategies are compared, highlighting their advantages and challenges. The paper concludes by identifying future research directions, challenges, and proposing strategies for the continued advancement of cost-effective and genetically engineered microalgal carotenoids for pharmaceutical applications.

Exploring effective light spectral conversion techniques for enhanced production of Spirulina-derived blue pigment protein, c-phycocyanin

Spirulina is a promising feedstock for c-phycocyanin, a blue pigment-protein, commercially incorporated in many food products for its desirable bright blue attributes, exceptional bioavailability, and inherent therapeutic properties. Remarkably, enhancing c-phycocyanin synthesis in Spirulina would facilitate economic viability and sustainability at large-scale production, as the forecasted market value is $ 409.8 million by 2030. Notably, the lighting source plays a key role in enhancing c-phycocyanin in Spirulina, and thus, strategies to filter/concentrate the photons of respective wavelengths, influencing light spectra, are beneficial. Enveloping open raceway ponds and greenhouses by luminescent solar concentrators and light filtering sheets enables solar spectral conversion of the sunlight at desirable wavelengths, emerges as a promising strategy to enhance synthesis of c-phycocyanin in Spirulina. Nevertheless, the conduction of techno-economic assessments and evaluation of scalability at large-scale cultivation of Spirulina are essential for the real-time implementation of lighting strategies.

Reaction of Pyrrolobenzothiazines with Schiff Bases and Carbodiimides: Approach to Angular 6/5/5/5-Tetracyclic Spiroheterocycles

1H-Pyrrole-2,3-diones, fused at [e]-side with a heterocycle, are suitable platforms for the synthesis of various angular polycyclic alkaloid-like spiroheterocycles. Recently discovered sulfur-containing [e]-fused 1H-pyrrole-2,3-diones (aroylpyrrolobenzothiazinetriones) tend to exhibit unusual reactivity. Based on these peculiar representatives of [e]-fused 1H-pyrrole-2,3-diones, we have developed an approach to an unprecedented 6/5/5/5-tetracyclic alkaloid-like spiroheterocyclic system of benzo[d]pyrrolo[3',4':2,3]pyrrolo[2,1-b]thiazole via their reaction with Schiff bases and carbodiimides. The experimental results have been supplemented with DFT computational studies. The synthesized alkaloid-like 6/5/5/5-tetracyclic compounds have been tested for their biotechnological potential as growth stimulants in the green algae Chlorella vulgaris.

Application of microbial resources in biorefineries: Current trend and future prospects

The recent growing interest in sustainable and alternative sources of energy and bio-based products has driven the paradigm shift to an integrated model termed "biorefinery." Biorefinery framework implements the concepts of novel eco-technologies and eco-efficient processes for the sustainable production of energy and value-added biomolecules. The utilization of microbial resources for the production of various value-added products has been documented in the literatures. However, the appointment of these microbial resources in integrated resource management requires a better understanding of their status. The main of aim of this review is to provide an overview on the defined positioning and overall contribution of the microbial resources, i.e., algae, fungi and bacteria, for various bioprocesses and generation of multiple products from a single biorefinery. By utilizing waste material as a feedstock, biofuels can be generated by microalgae while sequestering environmental carbon and producing value added compounds as by-products. In parallel, fungal biorefineries are prolific producers of lignocellulose degrading enzymes along with pharmaceutically important novel products. Conversely, bacterial biorefineries emerge as a preferred platform for the transformation of standard cells into proficient bio-factories, developing chassis and turbo cells for enhanced target compound production. This comprehensive review is poised to offer an intricate exploration of the current trends, obstacles, and prospective pathways of microbial biorefineries, for the development of future biorefineries.

Comparative Analysis of Effect of Culture Conditions on Growth and C-Phycocyanin Production in Helical and Linear Spirulina

Spirulina (Arthrospira and Spirulina spp.) has always been characterized by the helical trichomes, despite the existence of linear forms. A great debate is now open on the morphological flexibility of Spirulina, but it seems that both trichome morphology and C-phycocyanin (C-PC) concentrations are influenced by the culture conditions.This work compared the effect of some key growth factors (medium pH as well as its carbon, potassium, and salt contents) on the growth and C-PC concentration of helical and linear Spirulina strains. Further, two-phase strategies, including light and nitrogen variation, were applied to increase the in vivo C-PC accumulation into the trichomes. Results showed that high pH induced trichomes elongation and improved growth but decreased C-PC content (+ 65 and + 43% vs. -83 and -49%, for helical and linear strains, respectively). Variations in carbon and salt concentrations negatively impacted growth and C-PC content, even if the linear strain was more robust against these fluctuations. It was also interesting to see that potassium increasing improved growth and C-PC content for both strains.The variation of light wavelength during the enrichment phase (in the two-phase strategy) improved by 50% C-PC accumulation in trichomes, especially after blue lighting for 96 h. Similar result was obtained after 48 h of nitrogen reduction, while its removal from the medium caused trichomes disintegration. The current work highlights the robustness of linear Spirulina strain and presents an efficient and scalable way to increase C-PC in vivo without affecting growth.

Antares I: a Modular Photobioreactor Suitable for Photosynthesis and Bioenergetics Research

Oxygenic photosynthesis is responsible for most of the fixation of atmospheric CO2. The microalgal community can transport atmospheric carbon into biological cycles in which no additional CO2 is created. This represents a resource to confront the actual climate change crisis. These organisms have evolved to adapt to several environments and different spectral distribution of light that may strongly influence their metabolism. Therefore, there is a need for development of photobioreactors specialized in addressing spectral optimization. Here, a multi-scale modular photobioreactor made from standard glass materials, ad hoc light circuits, and easily accessible, small commercial devices is described. The system is suitable to manage the principal culture variables of research in bioenergetics and photosynthesis. Its performance was tested by growing four evolutionary-distant microalgal species with different endosymbiotic scenarios: Chlamydomonas reinhardtii (Archaeplastida, green primary plastid), Polytomella parva (Archaeplastida, colorless plastid), Euglena gracilis (Discoba, green secondary plastid), and Phaeodactylum tricornutum (Stramenophiles, red secondary plastid). Our results show an improvement of biomass production, as compared to the traditional flask system. The modulation of the incident light spectra allowed us to observe a far-red adaptation in Euglena gracilis with a difference on paramylon production, and it also significantly increased the maximal cell density of the diatom species under green light. Together, these confirm that for photobioreactors with artificial light, manipulation of the light spectrum is a critical parameter for controlling the optimal performance, depending on the downstream goals.

Enzymes as indispensable markers in disease diagnosis

Enzymes have been used for disease diagnosis for many decades; however, advancements in technology like ELISA and flow cytometry-based detection have significantly increased their use and have increased the sensitivity of detection. Technological advancements in recombinant enzyme production have increased enzymatic stability, and the use of colorimetric-based and florescence-based assays has led to their increased use as biomarkers for disease detection. Enzymes like acid phosphatase, cathepsin, lactate dehydrogenase, thymidine kinase and creatine kinase are indispensable markers for diagnosing cancer, cardiovascular diseases and others. This minireview summarizes various enzymes used in disease diagnosis, their metabolic role, market value and potential as disease markers across various metabolic and other disorders.

Improving the colloidal stability of pectin-phycocyanin complexes by increasing the mixing ratio

In the food industry, the phycobiliprotein phycocyanin acts as a color pigment or the functional part of the superfood "Spirulina." It is industrially extracted from Arthrospira platensis. Current scientific research is focusing on finding complex partners with the potential to stabilize phycocyanin against its sensitivity toward heating and pH changes. Less attention is paid to the factors that influence complexation. This study focuses on the mixing ratio of phycocyanin with pectin. Phycocyanin concentration was fixed, and the mixing ratios ranged from 0.67 to 2.50 (pectin:phycocyanin). All samples were analyzed for their color, size, microscopic structure, zeta potential, and sedimentation stability before and after heating at 85°C. It was found that increasing the pectin content fostered the initial interactions with the protein and chromophore, resulting in a color shift from blue to turquoise. The size of the complexes decreased from several micrometers to nanometers with increasing pectin concentration. Those smaller complexes that were formed at a mixing ratio of 2.5 showed a higher colloidal stability over a period of ∼2 days. It is suggested that at a low mixing ratio (0.67), phycocyanin cannot be completely entrapped within the complexes and attaches to the complex surface as well. This results in aggregation and precipitation of the complexes upon heating. With increasing aggregation and consequently size as well as density of the complexes, sedimentation was accelerated. PRACTICAL APPLICATION: Under acidic conditions, as found in many foods and beverages (e.g., soft drinks, hard candy), phycocyanin tends to agglomerate and lose its color. Specifically heating, triggers denaturation, causing phycocyanin to aggregate and lose vital protein-chromophore interactions necessary to maintain a blue color. To prevent precipitation of the phycocyanin-pectin complexes, increasing the amount of pectin to a ratio of at least 2.0 is effective. This illustrates how adjusting the mixing ratio improves stability. Conversely, lower mixing ratios  induce color precipitation, valuable in purification processes. Thus, practical use of biopolymer-complexes, requires determination of the optimal mixing ratio for the desired effect.

Microalgae-derived Co3O4 nanomaterials for catalytic CO oxidation

Efficient carbon monoxide oxidation is important to reduce its impacts on both human health and the environment. Following a sustainable synthesis route toward new catalysts, nanosized Co3O4 was synthesized based on extracts of microalgae: Spirulina platensis, Chlorella vulgaris, and Haematococcus pluvialis. Using the metabolites in the extract and applying different calcination temperatures (450, 650, 800 °C) led to Co3O4 catalysts with distinctly different properties. The obtained Co3O4 nanomaterials exhibited octahedral, nanosheet, and spherical morphologies with structural defects and surface segregation of phosphorous and potassium, originating from the extracts. The presence of P and K in the oxide nanostructures significantly improved their catalytic CO oxidation activity. When normalized by the specific surface area, the microalgae-derived catalysts exceeded a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction. The obtained insights may facilitate the development of new synthesis strategies for manufacturing highly active Co3O4 nanocatalysts.

The Structure, Functions and Potential Medicinal Effects of Chlorophylls Derived from Microalgae

Microalgae are considered to be natural producers of bioactive pigments, with the production of pigments from microalgae being a sustainable and economical strategy that promises to alleviate growing demand. Chlorophyll, as the main pigment of photosynthesis, has been widely studied, but its medicinal applications as an antioxidant, antibacterial, and antitumor reagent are still poorly understood. Chlorophyll is the most important pigment in plants and algae, which not only provides food for organisms throughout the biosphere, but also plays an important role in a variety of human and man-made applications. The biological activity of chlorophyll is closely related to its chemical structure; its specific structure offers the possibility for its medicinal applications. This paper reviews the structural and functional roles of microalgal chlorophylls, commonly used extraction methods, and recent advances in medicine, to provide a theoretical basis for the standardization and commercial production and application of chlorophylls.

Microbial pigments: Sources, current status, future challenges in cosmetics and therapeutic applications

Color serves as the initial attraction and offers a pleasing aspect. While synthetic colorants have been popular for many years, their adverse environmental and health effects cannot be overlooked. This necessitates the search for natural colorants, especially microbial colorants, which have proven and more effective. Pigment-producing microorganisms offer substantial benefits. Natural colors improve product marketability and bestow additional benefits, including antioxidant, antiaging, anticancer, antiviral, antimicrobial, and antitumor properties. This review covers the various types of microbial pigments, the methods to enhance their production, and their cosmetic and therapeutic applications. We also address the challenges faced during the commercial production of microbial pigments and propose potential solutions.

Comprehensive Update on Carotenoid Colorants from Plants and Microalgae: Challenges and Advances from Research Laboratories to Industry

The substitution of synthetic food dyes with natural colorants continues to be assiduously pursued. The current list of natural carotenoid colorants consists of plant-derived annatto (bixin and norbixin), paprika (capsanthin and capsorubin), saffron (crocin), tomato and gac fruit lycopene, marigold lutein, and red palm oil (α- and β-carotene), along with microalgal Dunaliella β-carotene and Haematococcus astaxanthin and fungal Blakeslea trispora β-carotene and lycopene. Potential microalgal sources are being sought, especially in relation to lutein, for which commercial plant sources are lacking. Research efforts, manifested in numerous reviews and research papers published in the last decade, have been directed to green extraction, microencapsulation/nanoencapsulation, and valorization of processing by-products. Extraction is shifting from conventional extraction with organic solvents to supercritical CO2 extraction and different types of assisted extraction. Initially intended for the stabilization of the highly degradable carotenoids, additional benefits of encapsulation have been demonstrated, especially the improvement of carotenoid solubility and bioavailability. Instead of searching for new higher plant sources, enormous effort has been directed to the utilization of by-products of the fruit and vegetable processing industry, with the application of biorefinery and circular economy concepts. Amidst enormous research activities, however, the gap between research and industrial implementation remains wide.

Enhancing the bio-prospective of microalgae by different light systems and photoperiods

Microalgae are a source of highly valuable bioactive metabolites and a high-potential feedstock for environmentally friendly and sustainable biofuel production. Recent research has shown that microalgae benefit the environment using less water than conventional crops while increasing oxygen production and lowering CO2 emissions. Microalgae are an excellent source of value-added compounds, such as proteins, pigments, lipids, and polysaccharides, as well as a high-potential feedstock for environmentally friendly and sustainable biofuel production. Various factors, such as nutrient concentration, temperature, light, pH, and cultivation method, effect the biomass cultivation and accumulation of high-value-added compounds in microalgae. Among the aforementioned factors, light is a key and essential factor for microalgae growth. Since photoautotrophic microalgae rely on light to absorb energy and transform it into chemical energy, light has a significant impact on algal growth. During micro-algal culture, spectral quality may be tailored to improve biomass composition for use in downstream bio-refineries and boost production. The light regime, which includes changes in intensity and photoperiod, has an impact on the growth and metabolic composition of microalgae. In this review, we investigate the effects of red, blue, and UV light wavelengths, different photoperiod, and different lighting systems on micro-algal growth and their valuable compounds. It also focuses on different micro-algal growth, photosynthesis systems, cultivation methods, and current market shares.

Metabolic engineering and synthetic biology strategies for producing high-value natural pigments in Microalgae

Microalgae are microorganisms capable of producing bioactive compounds using photosynthesis. Microalgae contain a variety of high value-added natural pigments such as carotenoids, phycobilins, and chlorophylls. These pigments play an important role in many areas such as food, pharmaceuticals, and cosmetics. Natural pigments have a health value that is unmatched by synthetic pigments. However, the current commercial production of natural pigments from microalgae is not able to meet the growing market demand. The use of metabolic engineering and synthetic biological strategies to improve the production performance of microalgal cell factories is essential to promote the large-scale production of high-value pigments from microalgae. This paper reviews the health and economic values, the applications, and the synthesis pathways of microalgal pigments. Overall, this review aims to highlight the latest research progress in metabolic engineering and synthetic biology in constructing engineered strains of microalgae with high-value pigments and the application of CRISPR technology and multi-omics in this context. Finally, we conclude with a discussion on the bottlenecks and challenges of microalgal pigment production and their future development prospects.

Diversity and impacts of macroalgae and cyanobacteria on multi-stressed coral reefs in the Gulf of Mannar Marine Biosphere Reserve

In India, intertidal seaweed resources are widely investigated and utilized for various applications, whereas reef-associated seaweed resources and their impacts on corals are lesser known. Thus, the present study investigated the diversity and impacts of macroalgae and cyanobacteria on coral reefs distributed in 21 islands under the Gulf of Mannar Marine Biosphere Reserve (GoMMBR), Tamil Nadu. About 140 macroalgal species representing 53 species of Chlorophyta, 32 species of Ochrophyta (Phaeophyta), and 55 species of Rhodophyta were recorded. Only three cyanobacterial species were documented during this study. All the documented species were categorized as edible, medicinal, smothering, bloom-forming, sediment trapping, and auxiliary. Diversity indices and multivariate analysis indicated latitudinal gradient distribution of macroalgae, where the maximum diversity was observed from the Mandapam group of Islands. The predominant genera observed in all the islands were Caulerpa, Halimeda, Turbinaria, and Sargassum. The updated checklist of seaweeds and cyanobacteria of India revealed 1118 and 258 species, correspondingly, on Indian coasts, including coral reef regions. The use of traditional morphology-based techniques in this study without molecular approaches to identify all of the specimens limits our investigation. Thus, molecular taxonomy is necessary to revalidate and confirm the actual genetic diversity existing in the Indian waters. Results of this study would benefit the scientific community and industries in various aspects, such as molecular taxonomy, biomass utilization, reef conservation, and industrial applications.

Chlamydomonas agloeformis from the Ecuadorian Highlands: Nutrients and Bioactive Compounds Profiling and In Vitro Antioxidant Activity

Green microalgae are single-celled eukaryotic organisms that, in recent years, are becoming increasingly important in the nutraceutical, cosmetic, and pharmaceutical fields because of their high content of bioactive compounds. In this study, a particular green microalga was isolated from freshwater highland lakes of Ecuador and morphologically and molecularly identified as Chlamydomonas agloeformis (ChA), and it was studied for nutritional and nutraceutical properties. The phenolic composition and the fatty acids profile of lyophilized cells were determined. The methanolic extract was analyzed for the phenolic compounds profile and the antioxidant capacity by means of in vitro tests. Finally, Human Microvascular Endothelial Cells (HMEC-1) were exploited to explore the capacity of ChA to reduce the endothelial damage induced by oxidized LDL-mediated oxidative stress. The extract showed a good antioxidant ability thanks to the high content in polyphenolic compounds. The observed decrease in HMEC-1 cells endothelial damage also was probably due to the antioxidant compounds present in the extract. Based on the outcomes of our in vitro assays, ChA demonstrated to be a promising source of bioactive compounds possessing exceptional antioxidant capacities which make it a prospective functional food.

Microalgae: A green eco-friendly agents for bioremediation of tannery wastewater with simultaneous production of value-added products

Tannery wastewater (TWW) has high BOD, COD, TS and variety of pollutants like chromium, formaldehydes, biocides, oils, chlorophenols, detergents and phthalates etc. Besides these pollutants, TWW also rich source of nutrients like nitrogen, phosphorus, carbon and sulphur etc. that can be utilized by microalgae during their growth. Direct disposal of TWW into the environment may lead severe environmental and health threats, therefore it needs to be treated adequately. Microalgae are considered as an efficient microorganisms (fast growing, adaptability and strain robustness, high surface to volume ratio, energy saving) for remediation of wastewaters with simultaneous biomass recovery and generation of value added products (VAPs) such as biofuels, biohydrogen, biopolymer, biofertilizer, pigments, bioethanol, bioactive compounds, nutraceutical etc. Most microalgae are photosynthetic and use CO₂ and light energy to synthesise carbohydrate and reduces the emission of greenhouse gasses. Microalgae are also reported to remove heavy metals and antibiotics from wastewaters by bioaccumulation, biodegradation and biosorption. Microalgal treatment can be an alternative of conventional processes with generation of VAPs. The use of biotechnology in wastewater remediation with simultaneous generation of VAPs is trending. The validation of economic viability and environmental sustainability, life cycle assessment studies and techno-economic analysis is undergoing. Thus, in this review, the characteristics of TWW and microalgae are summarized, which manifest microalgae as potential candidates for wastewater remediation with simultaneous production of VAPs. Further, the treatment mechanisms, various factors (physical, chemical, mechanical and biological etc.) affecting treatment efficiency as well as challenges associated with microalgal remediation are also discussed.

Simulation and Economic Analysis of the Biotechnological Potential of Biomass Production from a Microalgal Consortium

The biomass of microalgae and the compounds that can be obtained from their processing are of great interest for various economic sectors. Chlorophyll from green microalgae has biotechnological applications of great potential in different industrial areas such as food, animal feed, pharmaceuticals, cosmetics, and agriculture. In this paper, the experimental, technical and economic performance of biomass production from a microalgal consortium (Scenedesmus sp., Chlorella sp., Schroderia sp., Spirulina sp., Pediastrum sp., and Chlamydomonas sp.) was investigated in three cultivation systems (phototrophic, heterotrophic and mixotrophic) in combination with the extraction of chlorophyll (a and b) on a large scale using simulation; 1 ha was established as the area for cultivation. In the laboratory-scale experimental stage, biomass and chlorophyll concentrations were determined for 12 days. In the simulation stage, two retention times in the photobioreactor were considered, which generated six case studies for the culture stage. Subsequently, a simulation proposal for the chlorophyll extraction process was evaluated. The highest microalgae biomass concentration was 2.06 g/L in heterotrophic culture, followed by mixotrophic (1.98 g/L). Phototrophic and mixotrophic cultures showed the highest chlorophyll concentrations of 20.5 µg/mL and 13.5 µg/mL, respectively. The simulation shows that higher biomass and chlorophyll production is attained when using the mixotrophic culture with 72 h of retention that we considered to evaluate chlorophyll production (a and b). The operating cost of the entire process is very high; the cultivation stage has the highest operating cost (78%), mainly due to the high energy consumption of the photobioreactors.

Delivering impactful solutions for the bioeconomy

We are increasingly challenged to operate within our planetary boundaries, while delivering on United Nations (UN) Sustainable Development Goal (SDG) 2030 targets, and net-zero emissions by 2050. Failure to solve these challenges risks economic, social, political, climate, food, water, and fuel security. Therefore, new, scalable, and adoptable circular economy solutions are urgently required. The ability of plants to use light, capture CO₂, and drive complex biochemistry is pivotal to delivering these solutions. However, harnessing this capability efficiently also requires robust accompanying economic, financial, market, and strategic analytics. A framework for this is presented here in the Commercialization Tourbillon. It supports the delivery of emerging plant biotechnologies and bio-inspired light-driven industry solutions within the critical 2030-2050 timeframe, to achieve validated economic, social, and environmental benefits.

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.

Microalgae as a Nutraceutical Tool to Antagonize the Impairment of Redox Status Induced by SNPs: Implications on Insulin Resistance

Microalgae represent a growing innovative source of nutraceuticals such as carotenoids and phenolic compound which are naturally present within these single-celled organisms or can be induced in response to specific growth conditions. The presence of the unfavourable allelic variant in genes involved in the control of oxidative stress, due to one or more SNPs in gene encoding protein involved in the regulation of redox balance, can lead to pathological conditions such as insulin resistance, which, in turn, is directly involved in the pathogenesis of type 2 diabetes mellitus. In this review we provide an overview of the main SNPs in antioxidant genes involved in the promotion of insulin resistance with a focus on the potential role of microalgae-derived antioxidant molecules as novel nutritional tools to mitigate oxidative stress and improve insulin sensitivity.

Recent Advances in Supercritical CO2 Extraction of Pigments, Lipids and Bioactive Compounds from Microalgae

Supercritical CO₂ extraction is a green method that combines economic and environmental benefits. Microalgae, on the other hand, is a biomass in abundance, capable of providing a vast variety of valuable compounds, finding applications in the food industry, cosmetics, pharmaceuticals and biofuels. An extensive study on the existing literature concerning supercritical fluid extraction (SFE) of microalgae has been carried out focusing on carotenoids, chlorophylls, lipids and fatty acids recovery, as well as the bioactivity of the extracts. Moreover, kinetic models used to describe SFE process and experimental design are included. Finally, biomass pretreatment processes applied prior to SFE are mentioned, and other extraction methods used as benchmarks are also presented.

The antioxidant, wound healing properties and proteomic analysis of water extracts from the tropical cyanobacteria, Nostoc NIES-2111_MUM004

Cyanobacteria bioactive compounds are chemical treasure troves for product discovery and development. The wound healing effects and antioxidant capacities of water extracts from Nostoc NIES-2111_MUM004 were evaluated via in vitro wound scratch assay and three antioxidant assays respectively. Results showed that the water extracts were protein-rich and exhibited good antioxidant properties in ABTS radical scavenging (11.27 ± 0.205 mg TAE g^-1 extract), Ferric reducing antioxidant power (1652.71 ± 110.71 mg TAE g^-1 extract) and β-carotene bleaching assay (354.90 ± 31.80 mg TAE g^-1 extract). Also, extracts were non-cytotoxic in concentrations up to 250 µg/mL as reflected in cytotoxicity assay. Importantly, water extracts showed considerable proliferation and migration activity at 125 µg/mL with wound closure rate as high as 42.67%. Statistical correlation revealed no significant relationship (p > 0.05) between protein fraction and the wound healing properties, confirming that phycobiliproteins were not solely responsible for wound healing activities. Subsequent Q-TOF-LCMS analysis identified six protein families involved in enhancing the proliferation and migration of epithelial cells. These findings are antecedent in the uncovering of continuous supplies of bioactive compounds from new and sustainable sources. Ultimately, enriching the microalgae menu for applications in pharmaceutical, nutraceutical and cosmeceuticals.

Egg laying performance and egg quality with Paracoccus carotinifaciens supplementation containing high astaxanthin levels

1. This study assessed 1) the effects of Paracoccus carotinifaciens supplementation containing high astaxanthin levels on egg production performance and quality, 2) dynamics of carotenoids levels in the egg yolk and 3) taste of astaxanthin-rich egg yolk.2. Laying hens were fed diets containing different levels of P. carotinifaciens-derived astaxanthin (ASX; 0, 2, 4, 8, or 16 ppm) for 28 d (experiment 1) or a diet containing 16 ppm astaxanthin for 28 d followed by a 0 ppm astaxanthin diet for 28 days (experiment 2).3. Production performance, egg quality and egg yolk carotenoid levels were examined in experiment 1 (Ex1) and the dynamics of egg yolk carotenoid levels and egg yolk taste in experiment 2 (Ex2).4. ASX supplementation did not affect production performance or egg quality. ASX levels in the egg yolk became saturated after seven days of 16 ppm supplementation and decreased to less than one-tenth of the saturated levels seven days after supplementation cessation. Supplementation with 16 ppm ASX for 28 d did not affect egg yolk taste.5. Supplementation resulted in the production of ASX-rich eggs for a brief period without affecting production performance, egg quality or taste. Understanding the time taken for the incorporation of ASX into egg yolks is beneficial for value-added egg production and may help in minimising supplementation costs.

Microalgae-Derived Pigments for the Food Industry

In the food industry, manufacturers and customers have paid more attention to natural pigments instead of the synthetic counterparts for their excellent coloring ability and healthy properties. Microalgae are proven as one of the major photosynthesizers of naturally derived commercial pigments, gaining higher value in the global food pigment market. Microalgae-derived pigments, especially chlorophylls, carotenoids and phycobiliproteins, have unique colors and molecular structures, respectively, and show different physiological activities and health effects in the human body. This review provides recent updates on characteristics, application fields, stability in production and extraction processes of chlorophylls, carotenoids and phycobiliproteins to standardize and analyze their commercial production from microalgae. Potential food commodities for the pigment as eco-friendly colorants, nutraceuticals, and antioxidants are summarized for the target products. Then, recent cultivation strategies, metabolic and genomic designs are presented for high pigment productivity. Technical bottlenecks of downstream processing are discussed for improved stability and bioaccessibility during production. The production strategies of microalgal pigments have been exploited to varying degrees, with some already being applied at scale while others remain at the laboratory level. Finally, some factors affecting their global market value and future prospects are proposed. The microalgae-derived pigments have great potential in the food industry due to their high nutritional value and competitive production cost.

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.

Comparative genomic analysis illustrates evolutionary dynamics of multisubunit tethering complexes across green algal diversity

The chlorophyte algae are a dominant group of photosynthetic eukaryotes. Although many are photoautotrophs, there are also mixotrophs, heterotrophs, and even parasites. The physical characteristics of green algae are also highly diverse, varying greatly in size, shape, and habitat. Given this morphological and trophic diversity, we postulated that diversity may also exist in the protein components controlling intracellular movement of material by vesicular transport. One such set is the multisubunit tethering complexes (MTCs)-components regulating cargo delivery. As they span endomembrane organelles and are well-conserved across eukaryotes, MTCs should be a good proxy for assessing the evolutionary dynamics across the diversity of Chlorophyta. Our results reveal that while green algae carry a generally conserved and unduplicated complement of MTCs, some intriguing variation exists. Notably, we identified incomplete sets of TRAPPII, exocyst, and HOPS/CORVET components in all Mamiellophyceae, and what is more, not a single subunit of Dsl1 was found in Cymbomonas tetramitiformis. As the absence of Dsl1 has been correlated with having unusual peroxisomes, we searched for peroxisome biogenesis machinery, finding very few components in Cymbomonas, suggestive of peroxisome degeneration. Overall, we demonstrate conservation of MTCs across green algae, but with notable taxon-specific losses suggestive of unusual endomembrane systems.

Algal Biomass Accumulation in Waste Digestate after Anaerobic Digestion of Wheat Straw

Cultivation of microalgae in waste digestate is a promising cost-effective and environmentally friendly strategy for algal biomass accumulation and valuable product production. Two different digestates obtained as by-products of the anaerobic fermentation at 35 °C and 55 °C of wheat straw as a renewable source for biogas production in laboratory-scale bioreactors were tested as cultivation media for microalgae after pretreatment with active carbon for clarification. The strains of microalgae involved were the red marine microalga Porphyridium cruentum, which reached 4.7 mg/mL dry matter when grown in thermophilic digestate and green freshwater microalga-Scenedesmus acutus, whose growth was the highest—7.3 mg/mL in the mesophilic digestate. During cultivation, algae reduced the available nutrient components in the liquid digestate at the expense of increasing their biomass. This biomass can find further applications in cosmetics, pharmacy, and feed. The nitrogen and phosphorus uptake from both digestates during algae cultivation was monitored and modeled. The results led to the idea of nonlinear dynamic approximations with an exponential character. The purpose was to develop relatively simple nonlinear dynamic models based on available experimental data, as knowing the mechanisms of the considered processes can permit creating protocols for industrial-scale algal production toward obtaining economically valuable products from microalgae grown in organic waste digestate.

Self-Enclosed Bio-Photoelectrochemical Cell in Succulent Plants

Harvesting an electrical current from biological photosynthetic systems (live cells or isolated complexes) is typically achieved by immersion of the system into an electrolyte solution. In this study, we show that the aqueous solution found in the tissues of succulent plants can be used directly as a natural bio-photo electrochemical cell. Here, the thick water-preserving outer cuticle of the succulent Corpuscularia lehmannii serves as the electrochemical container, the inner water content as the electrolyte into which an iron anode and platinum cathode are introduced. We produce up to 20 μA/cm² bias-free photocurrent. When 0.5 V bias is added to the iron anode, the current density increases ∼10-fold, and evolved hydrogen gas can be collected with a Faradaic efficiency of 2.1 and 3.5% in dark or light, respectively. The addition of the photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea inhibits the photocurrent, indicating that water oxidation is the primary source of electrons in the light. Two-dimensional fluorescence measurements show that NADH and NADPH serve as the major mediating electron transfer molecules, functionally connecting photosynthesis to metal electrodes. This work presents a method to simultaneously absorb CO₂ while producing an electrical current with minimal engineering requirements.

Functional properties of bioactive compounds from Spirulina spp.: Current status and future trends

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Functional foods that contain bioactive compounds (BC) and provide health benefits;

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Spirulina is a cyanobacterium considered blue microalgae rich in BC;

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BC from Spirulina have interesting health effects;

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Chlorophyll, carotenoids, and phycocyanin are natural corants from Spirulina;

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Spirulina has potential as an ingredient for application in functional foods.

Functional foods show non-toxic bioactive compounds that offer health benefits beyond their nutritional value and beneficially modulate one or more target functions in the body. In recent decades, there has been an increase in the trend toward consuming foods rich in bioactive compounds, less industrialized, and with functional properties. Spirulina, a cyanobacterium considered blue microalgae, widely found in South America, stands out for its rich composition of bioactive compounds, as well as unsaturated fatty acids and essential amino acids, which contribute to basic human nutrition and can be used as a protein source for diets free from animal products. In addition, they have colored compounds, such as chlorophylls, carotenoids, phycocyanins, and phenolic compounds which can be used as corants and natural antioxidants. In this context, this review article presents the main biological activities of spirulina as an anticancer, neuroprotective, probiotic, anti-inflammatory, and immune system stimulating effect. Furthermore, an overview of the composition of spirulina, its potential for different applications in functional foods, and its emerging technologies are covered in this review.

Cultivation of microalgae on food waste: Recent advances and way forward

Microalgae are photosynthetic microbes that can synthesize compounds of therapeutic potential with wide applications in the food, bioprocessing and pharmaceutical sector. Recent research advances have therefore, focused on finding suitable economic substrates for the sustainable cultivation of microalgae. Among such substrates, food derived waste specifically from the starch, meat, dairy, brewery, oil and fruit and vegetable processing industries has gained popularity but poses numerous challenges. Pretreatment, dilution of waste water supernatants, mixing of different food waste streams, utilizing two-stage cultivation and other biorefinery approaches have been intensively explored for multifold improvement in microalgal biomass recovery from food waste. This review discusses the advances and challenges associated with cultivation of microalgae on food waste. The review suggests that there is a need to standardize different waste substrates in terms of general composition, genetically engineered microalgal strains, tackling process scalability issues, controlling wastewater toxicity and establishing a waste transportation chain.

Algal biorefinery culminating multiple value-added products: recent advances, emerging trends, opportunities, and challenges

Algal biorefinery is rising as a prominent solution to economically fulfill the escalating global requirement for nutrition, feed, fuel, and medicines. In recent years, scientific productiveness associated with microalgae-based studies has elaborated in multiplied aspects, while translation to the commercial level continues to be missing. The present microalgal biorefinery has a challenge in long-term viability due to escalated market price of algal-mediated biofuels and bioproducts. Advancements are required in a few aspects like improvement in algae processing, energy investment, and cost analysis of microalgae biorefinery. Therefore, it is essential to recognize the modern work by understanding the knowledge gaps and hotspots driving business scale up. The microalgae biorefinery integrated with energy-based products, bioactive and green compounds, focusing on a circular bioeconomy, is urgently needed. A detailed investigation of techno-economic analysis (TEA) and life cycle assessment (LCA) is important to increase the market value of algal products. This review discusses the valorization of algal biomass for the value-added application that holds a sustainable approach and cost-competitive algal biorefinery. The current industries, policies, technology transfer trends, challenges, and future economic outlook are discussed. This study is an overview through scientometric investigation attempt to describe the research development contributing to this rising field.

Bioproducts from microalgae biomass: Technology, sustainability, challenges and opportunities

Microalgae are a potential feedstock for several bioproducts, mainly from its primary and secondary metabolites. Lipids can be converted in high-value polyunsaturated fatty acids (PUFA) such as omega-3, carbohydrates are potential biohydrogen (bioH₂) sources, proteins can be converted into biopolymers (such as bioplastics) and pigments can achieve high concentrations of valuable carotenoids. This work comprehends the current practices for the production of such products from microalgae biomass, with insights on technical performance, environmental and economical sustainability. For each bioproduct, discussion includes insights on bioprocesses, productivity, commercialization, environmental impacts and major challenges. Opportunities for future research, such as wastewater cultivation, arise as environmentally attractive alternatives for sustainable production with high potential for resource recovery and valorization. Still, microalgae biotechnology stands out as an attractive topic for it research and market potential.

Progress of Microencapsulated Phycocyanin in Food and Pharma Industries: A Review

Phycocyanin is a blue fluorescent protein with multi-bioactive functions. However, the multi-bioactivities and spectral stability of phycocyanin are susceptible to external environmental conditions, which limit its wide application. Here, the structure, properties, and biological activity of phycocyanin were discussed. This review highlights the significance of the microcapsules' wall materials which commonly protect phycocyanin from environmental interference and summarizes the current preparation principles and characteristics of microcapsules in food and pharma industries, including spray drying, electrospinning, electrospraying, liposome delivery, sharp-hole coagulation baths, and ion gelation. Moreover, the major technical challenge and corresponding countermeasures of phycocyanin microencapsulation are also appraised, providing insights for the broader application of phycocyanin.