Use of pulsed electric field permeabilization to extract astaxanthin from the Nordic microalga Haematococcus pluvialis

Bioactive Compounds of Marine Algae and Their Potential Health and Nutraceutical Applications: A Review

Currently, marine algae are still an under-exploited natural bioresource of bioactive compounds. Seaweeds represent a sustainable source for obtaining bioactive compounds that can be useful for the fabrication of new active products with biomedical benefits and applications as biomedicinals and nutraceuticals. The objective of this review is to highlight scientific papers that identify biocompounds from marine macroalgae and emphasize their benefits. The method used was data analysis to systematize information to identify biocompounds and their various benefits in pharmaceuticals, cosmetics, and nutraceuticals. The research results demonstrate the multiple uses of seaweeds. As pharmaceuticals, seaweeds are rich sources of bioactive compounds like polysaccharides, protein compounds, pigments, and polyphenols, which have demonstrated various pharmacological activities such as antioxidant, antibacterial, anti-inflammatory, antiviral, anticoagulant, and potentially anticarcinogenic effects. Seaweed has gained recognition as a functional food and offers a unique set of compounds that promote body health, including vitamins, minerals, and antioxidants. In conclusion, the importance of this review is to expand the possibilities for utilizing natural resources by broadening the areas of research for human health and marine nutraceuticals.

Microalgae-derived astaxanthin: bioactivities, biotechnological approaches and industrial technologies for its production

Microalgae are rich sources of astaxanthin well recognized for their potent bioactivities such as antioxidant, anti-cancer, and anti-inflammatory activities. Recent interests focused on the bioactivities of microalgae-derived astaxanthin on treating or preventing cancers mediated by their antioxidant and anti-inflammatory properties. This is due to the special structural configuration of microalgae-derived astaxanthin in terms of unsaturation (conjugated double bonds), stereochemical isomerism (3S,3'S optical isomer) and esterification (monoester), which display more potent bioactivities, compared with those from the other natural sources such as yeasts and higher plants, as well as synthetic astaxanthin. This review focuses on the recent advances on the bioactivities of microalgae-derived astaxanthin in association with cancers and immune diseases, with emphasis on their potential applications as natural antioxidants. Various well-developed biotechnological approaches for inducing astaxanthin production from microalgal culture, along with the proven and emerging industrial technologies to commercialize astaxanthin products in a large-scale manner, are also critically reviewed. These would facilitate the manufacture of bioactive microalgae-derived astaxanthin products to be applied in the food and pharmaceutical industries as salutary nutraceuticals.

Biphasic lipid extraction from microalgae after PEF-treatment reduces the energy demand of the downstream process

BACKGROUND

The gradual extrusion of water-soluble intracellular components (such as proteins) from microalgae after pulsed electric field (PEF) treatment is a well-documented phenomenon. This could be utilized in biorefinery applications with lipid extraction taking place after such an 'incubation' period, i.e., a post-PEF-treatment step during which the biomass is left undisturbed before any further processing. The goal of this work was to further explore how this incubation could improve lipid extraction.

RESULTS

Experiments were conducted on wet, freshly harvested Auxenochlorella protothecoides, treated with 0.25 or 1.5 MJ/kgDW and incubated for 24 h. Lipid extraction took place with a monophasic ethanol:hexane:water, 1:0.41:0.04 vol/vol/vol mixture with a 75.6 mL solvent per 1 g of dry biomass ratio. The kinetics of the extraction were studied with samples taken between 10 and 1080 min from fresh and incubated biomass. The yields at 10 min were significantly increased with incubation compared to without (31.2% dry weight compared to 1.81%, respectively). The experimental data were fitted with the Patricelli model where extraction occurs in two steps, a rapid washing of immediate available lipids and a slower diffusion one. During Nile-Red staining of microalgae and microscopy imaging, a shift of emission from both GFP and RFP channels to mostly RFP was observed indicating an increase in the polarity of the environment of Nile-Red. These led to an adaption of a biphasic ethanol:hexane:water 1:6:0.4 vol/vol/vol solvent with 37 mL solvent per 1 g of dry biomass ratio which while ineffective on fresh biomass, achieved a 27% dry weight yield from incubated microalgae. The extraction efficiency in the biphasic route was lower compared to the monophasic (i.e., 69% and 95%, respectively). It was compensated however, by the significant solvent reduction (37 mL to 75.6 mL respectively), in particular the ethanol minimization. For the extraction of 1 L lipids, it was estimated that the energy consumption ratio for the biphasic process was 1.6 compared to 9.9 for monophasic, making clearly the most preferential one.

CONCLUSIONS

This biphasic approach significantly reduces solvent consumption and the respective energy requirement for solvent recovery. Incubation thus could majorly improve the commercialization prospects of the process.

Evaluation of astaxanthin stability under varying temperatures and ultraviolet irradiation durations based on Raman spectroscopy

As a potent naturally carotenoid, Astaxanthin (AST) is commonly used as a natural coloring agent and antioxidant in food products, and it's stability is of great interest. The stability of AST solution stored in glass bottle under different temperatures and ultraviolet (UV) irradiation durations was analyzed in situ using confocal Raman spectroscopy, and the acceptable depth of focus was optimized. Raman spectra of AST geometrical isomers were determined by density functional theory (DFT) simulation, and characteristic peaks were selected for studying AST degradation and isomerization. Raman spectra and peak-fitting spectra based on gaussian multi-peak fitting analysis combined with Pearson's correlation analysis were conducted to study the effect of temperatures and UV irradiation on AST degradation and isomerization. The peak intensity ratio of I1518/I880 had been selected as the optimal Raman spectral variable for AST degradation based on Pearson's correlation analysis. Finally, degradation kinetic curves and degradation rate prediction equation were established. The results indicated that the isomerization of 9,13-di-cis isomer occurred at a UV irradiation of 288 h. Moreover, high temperatures above 60 °C and prolonged UV exposure exceeds 48 h can cause significant degradation of AST, with a degradation rate above 20 %. This study provided an in-situ, nondestructive potential method for the calculation of AST degradation under different temperatures and UV irradiation durations, which contribute guiding insights into the development and utilization of AST in food industry.

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.

Pulsed Electric Fields Effects on Proteins: Extraction, Structural Modification, and Enhancing Enzymatic Activity

Pulsed electric field (PEF) is an innovative physical method for food processing characterized by low energy consumption and short processing time. This technology represents a sustainable procedure to extend food shelf-life, enhance mass transfer, or modify food structure. The main mechanism of action of PEF for food processing is the increment of the permeability of the cell membranes by electroporation. However, it has also been shown that PEF may modify the technological and functional properties of proteins. Generating a high-intensity electric field necessitates the flow of an electric current that may have side effects such as electrochemical reactions and temperature increments due to the Joule effect that may affect food components such as proteins. This article presents a critical review of the knowledge on the extraction of proteins assisted by PEF and the impact of these treatments on protein composition, structure, and functionality. The required research for understanding what happens to a protein when it is under the action of a high-intensity electric field and to know if the mechanism of action of PEF on proteins is different from thermal or electrochemical effects is underlying.

Sustainable Green Extraction of Carotenoid Pigments: Innovative Technologies and Bio-Based Solvents

Carotenoids are ubiquitous and versatile isoprenoid compounds. The intake of foods rich in these pigments is often associated with health benefits, attributable to the provitamin A activity of some of them and different mechanisms. The importance of carotenoids and their derivatives for the production of foods and health-promotion through the diet is beyond doubt. In the new circular economy paradigm, the recovery of carotenoids in the biorefinery process is highly desirable, for which greener processes and solvents are being advocated for, considering the many studies being conducted at the laboratory scale. This review summarizes information on different extraction technologies (ultrasound, microwaves, pulsed electric fields, pressurized liquid extraction, sub- and supercritical fluid extraction, and enzyme-assisted extraction) and green solvents (ethyl lactate, 2-methyltetrahydrofuran, natural deep eutectic solvents, and ionic liquids), which are potential substitutes for more toxic and less environmentally friendly solvents. Additionally, it discusses the results of the latest studies on the sustainable green extraction of carotenoids. The conclusions drawn from the review indicate that while laboratory results are often promising, the scalability to real industrial scenarios poses a significant challenge. Furthermore, incorporating life cycle assessment analyses is crucial for a comprehensive evaluation of the sustainability of innovative extraction processes compared to industry-standard methods.

A review on pretreatment methods for lipid extraction from microalgae biomass

Microalgal lipids are promising and sustainable sources for the production of third-generation biofuels, foods, and medicines. A high lipid yield during the extraction process in microalgae could be influenced by the suitable pretreatment and lipid extraction methods. The extraction method itself could be attributed to the economic and environmental impacts on the industry. This review summarizes the pretreatment methods including mechanical and non-mechanical techniques for cell lysis strategy before lipid extraction in microalgae biomass. The multiple strategies to achieve high lipid yields via cell disruption techniques are discussed. These strategies include mechanical (shear forces, pulse electric forces, waves, and temperature shock) and non-mechanical (chemicals, osmotic pressure, and biological) methods. At present, two techniques of the pretreatment method can be combined to increase lipid extraction from microalgae. Therefore, the extraction strategy for a large-scale application could be further strengthened to optimize lipid recovery by microalgae.

Astaxanthin from microalgae: A review on structure, biosynthesis, production strategies and application

Astaxanthin is a red-colored secondary metabolite with excellent antioxidant properties, typically finds application as foods, feed, cosmetics, nutraceuticals, and medications. Astaxanthin is usually produced synthetically using chemicals and costs less as compared to the natural astaxanthin obtained from fish, shrimps, and microorganisms. Over the decades, astaxanthin has been naturally synthesized from Haematococcus pluvialis in commercial scales and remains exceptional, attributed to its higher bioactive properties as compared to synthetic astaxanthin. However, the production cost of algal astaxanthin is still high due to several bottlenecks prevailing in the upstream and downstream processes. To that end, the present study intends to review the recent trends and advancements in astaxanthin production from microalgae. The structure of astaxanthin, sources, production strategies of microalgal astaxanthin, and factors influencing the synthesis of microalgal astaxanthin were discussed while detailing the pathway involved in astaxanthin biosynthesis. The study also discusses the relevant downstream process used in commercial scales and details the applications of astaxanthin in various health related issues.

Enhancement of astaxanthin production, recovery, and bio-accessibility in Haematococcus pluvialis through taurine-mediated inhibition of secondary cell wall formation under high light conditions

This study explored the use of taurine in enhancing the production and bio-accessibility of astaxanthin in Haematococcus pluvialis, which typically forms a secondary cell wall hindering astaxanthin extraction. The biomass of taurine-treated group significantly increased by 18%, and astaxanthin yield surged by 34% in comparison to the control group. Without cell disruption, astaxanthin recovery from thin-walled cells in the taurine-treated group, using dimethyl sulfoxide and ethanol as extraction reagents, was 97% and 75%, respectively, which were 30-fold higher than those of thick-walled cells in the control group. Additionally, the cell fragmentation rate increased by 86% in taurine-treated group relative to the control group. Comparative transcriptome analysis identified taurine-induced upregulation of genes involved in the astaxanthin biosynthesis pathway and downregulation of those associated with secondary cell wall synthesis. This study thus offers an innovative taurine-based strategy to enhance astaxanthin production and bio-accessibility while shedding light on the mechanisms driving this process.

Microalgae, Seaweeds and Aquatic Bacteria, Archaea, and Yeasts: Sources of Carotenoids with Potential Antioxidant and Anti-Inflammatory Health-Promoting Actions in the Sustainability Era

Carotenoids are a large group of health-promoting compounds used in many industrial sectors, such as foods, feeds, pharmaceuticals, cosmetics, nutraceuticals, and colorants. Considering the global population growth and environmental challenges, it is essential to find new sustainable sources of carotenoids beyond those obtained from agriculture. This review focuses on the potential use of marine archaea, bacteria, algae, and yeast as biological factories of carotenoids. A wide variety of carotenoids, including novel ones, were identified in these organisms. The role of carotenoids in marine organisms and their potential health-promoting actions have also been discussed. Marine organisms have a great capacity to synthesize a wide variety of carotenoids, which can be obtained in a renewable manner without depleting natural resources. Thus, it is concluded that they represent a key sustainable source of carotenoids that could help Europe achieve its Green Deal and Recovery Plan. Additionally, the lack of standards, clinical studies, and toxicity analysis reduces the use of marine organisms as sources of traditional and novel carotenoids. Therefore, further research on the processing of marine organisms, the biosynthetic pathways, extraction procedures, and examination of their content is needed to increase carotenoid productivity, document their safety, and decrease costs for their industrial implementation.

Exploring Nordic microalgae as a potential novel source of antioxidant and bioactive compounds

Nordic microalgae are a group of photosynthetic organisms acclimated to growth at low temperature and in varying light conditions; the subarctic climate offers bright days with moderate temperatures during summer and cold and dark winter months. The robustness to these natural stress conditions makes the species interesting for large-scale cultivation in harsh environments and for the production of high-value compounds. The aim of this study was to explore the ability of nineteen species of Nordic microalgae to produce different bioactive compounds, such as carotenoids or polyphenols. The results showed that some of these strains are able to produce high amounts of carotenoids (over 12 mg·g^-1 dry weight) and phenolic compounds (over 20 mg GAE·g^-1 dry weight). Based on these profiles, six species were selected for cultivation under high light and cold stress (500 μmol·m^-2·s^-1 and 10 ˚C). The strains Chlorococcum sp. (MC1) and Scenedesmus sp. (B2-2) exhibited similar values of biomass productivity under standard or stress conditions, but produced higher concentrations of carotenoids (an increase of 40% and 25%, respectively), phenolic compounds (an increase of 40% and 30%, respectively), and showed higher antioxidant capacity (an increase of 15% and 20%, respectively) during stress. The results highlight the ability of these Nordic microalgae as outstanding producers of bioactive compounds, justifying their cultivation at large scale in Nordic environments.

Extraction of Valuable Biomolecules from the Microalga Haematococcus pluvialis Assisted by Electrotechnologies

The freshwater microalga Haematococcus pluvialis is well known as the cell factory for natural astaxanthin, which composes up to 4-7% of its total dry weight. The bioaccumulation of astaxanthin in H. pluvialis cysts seems to be a very complex process that depends on different stress conditions during its cultivation. The red cysts of H. pluvialis develop thick and rigid cell walls under stress growing conditions. Thus, the biomolecule extraction requires general cell disruption technologies to reach a high recovery rate. This short review provides an analysis of the different steps in H. pluvialis's up and downstream processing including cultivation and harvesting of biomass, cell disruption, extraction and purification techniques. Useful information on the structure of H. pluvialis's cells, biomolecular composition and properties and the bioactivity of astaxanthin is collected. Special emphasis is given to the recent progress in application of different electrotechnologies during the growth stages and for assistance of the recovery of different biomolecules from H. pluvialis.

Current trends in the pretreatment of microalgal biomass for efficient and enhanced bioenergy production

Biofuels from microalgal biomass is among some of the promising sustainable energy technologies that can significantly replace the dependence on fossil fuels worldwide due to potentiality to lower CO₂ emissions. Nevertheless, the extraction of biomolecules for biofuel generation is inhibited by the rigidity of the cellular structure of microalgal biomass. Various pretreatment strategies have been evaluated for their efficacy in microalgal cell wall disruption to enhance microalgal bioenergy production. However, the efficiency of the pretreatment methods depend on the particular species being treated due to the inherent variability of the composition of the cell wall. This paper reviews pretreatment strategies (mainly novel physical, chemical and physicochemical) employed in bioenergy generation from microalgal biomass, address existing constraints and provides prospects for economic and industrial-scale production. The authors have also discussed the different pretreatment methods used for biodiesel, bioethanol, and biohydrogen production.

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.

Cell disruption and lipid extraction from Chlorella species for biorefinery applications: Recent advances

Chlorella is a promising microalga for CO₂-neutral biorefinery that co-produces drop-in biofuels and multiple biochemicals. Cell disruption and selective lipid extraction steps are major technical bottlenecks in biorefinement because of the inherent robustness and complexity of algal cell walls. This review focuses on the state-of-the-art achievements in cell disruption and lipid extraction methods for Chlorella species within the last five years. Various chemical, physical, and biological approaches have been detailed theoretically, compared, and discussed in terms of the degree of cell wall disruption, lipid extractability, chemical toxicity, cost-effectiveness, energy use, scalability, customer preferences, environment friendliness, and synergistic combinations of different methods. Future challenges and prospects of environmental-friendly and efficient extraction technologies are also outlined for practical applications in sustainable Chlorella biorefineries. Given the diverse industrial applications of Chlorella, this review may provide useful information for downstream processing of the advanced biorefineries of other algae genera.

Recent advancements in astaxanthin production from microalgae: A review

Microalgae have emerged as the best source of high-value astaxanthin producers. Algal astaxanthin possesses numerous bioactivities hence the rising demand for several health applications and is broadly used in pharmaceuticals, aquaculture, health foods, cosmetics, etc. Among several low-priced synthetic astaxanthin, natural astaxanthin is still irreplaceable for human consumption and food-additive uses. This review highlights the recent development in production enhancement and cost-effective extraction techniques that may apply to large-scale astaxanthin biorefinery. Primarily, the biosynthetic pathway of astaxanthin is elaborated with the key enzymes involved in the metabolic process. Moreover, discussed the latest astaxanthin enhancement strategies mainly including chemicals as product inducers and byproducts inhibitors. Later, various physical, chemical, and biological cell disruption methods are compared for cell disruption efficiency, and astaxanthin extractability. The aim of this review is to provide a comprehensive review of advancements in astaxanthin research covering scalable upstream and downstream astaxanthin bioproduction aspects.

Algae in wastewater treatment, mechanism, and application of biomass for production of value-added product

The pollutants can enter water bodies at various point and non-point sources, and wastewater discharge remains a major pathway. Wastewater treatment effectively reduces contaminants, it is expensive and requires an eco-friendly and sustainable alternative approach to reduce treatment costs. Algae have recently emerged as a potentially cost-effective method to remediate toxic pollutants through the mechanism of biosorption, bioaccumulation, and intracellular degradation. Hence, before discharging the wastewater into the natural environment better solutions for environmental resource recovery and sustainable developments can be applied. More importantly, algae are a potential feedstock material for various industrial applications such as biofuel production. Currently, researchers are developing algae as a source for pharmaceuticals, biofuels, food additives, and bio-fertilizers. This review mainly focused on the potential of algae and their specific mechanisms involved in wastewater treatment and energy recovery systems leading to important industrial precursors. The review is highly beneficial for scientists, wastewater treatment plant operators, freshwater managers, and industrial communities to support the sustainable development of natural resources.

Detailed Characterization of the Cell Wall Structure and Composition of Nordic Green Microalgae

Green microalgae are attractive to food, pharmaceutical, and biofuel industries due to the promising and diverse properties of their intracellular components. In current biotechnological applications, however, clear bottlenecks are the cell disruption and cell harvesting steps. Challenges in both of these processes are directly linked to the properties of the microalgal cell wall. The aim of this study was to explore the cell wall compositions and morphologies of four Nordic microalgal strains (Chlorella vulgaris (13-1), Scenedesmus sp. (B2-2), Haematococcus pluvialis, and Coelastrella sp. (3-4)) and their changes in relation to logarithmic and stationary growth phases. Transmission electron microscopy imaging enabled us to visualize the cell walls and to observe structural elements such as spines, microfibrillar hairs, or layers. Using cryogenic X-ray photoelectron spectroscopy, we quantified lipid, protein, and polysaccharide content of the outer surface of the microalgal cell wall in cultures. Fourier transform infrared spectroscopy highlighted changes between growth phases within the polysaccharide and protein fractions of the cell wall. Very prominent differences were observed in sugar and protein composition of the Scenedesmus sp. (B2-2) cell wall compared to the cell walls of the other three Nordic strains using trimethylsilyl derivatization.

Decay of Trichomes of Arthrospira platensis After Permeabilization Through Pulsed Electric Fields (PEFs) Causes the Release of Phycocyanin

The cyanobacterium Arthrospira platensis is a promising source of edible proteins and other highly valuable substances such as the blue pigment-protein complex phycocyanin. Pulsed electric field (PEF) technology has recently been studied as a way of permeabilizing the cell membrane, thereby enhancing the mass transfer of water-soluble cell metabolites. Unfortunately, the question of the release mechanism is not sufficiently clarified in published literature. In this study, the degree of cell permeabilization (cell disintegration index) was directly measured by means of a new method using fluorescent dye propidium iodide (PI). The method allows for conclusions to be drawn about the effects of treatment time, electric field strength, and treatment temperature. Using a self-developed algorithm for image segmentation, disintegration of trichomes was observed over a period of 3 h. This revealed a direct correlation between cell disintegration index and decay of trichomes. This decay, in turn, could be brought into a direct temporal relationship with the release of phycocyanin. For the first time, this study reveals the relationship between permeabilization and the kinetics of particle decay and phycocyanin extraction, thus contributing to a deeper understanding of the release of cell metabolites in response to PEF. The results will facilitate the design of downstream processes to produce sustainable products from Arthrospira platensis.

Insights into using green and unconventional technologies to recover natural astaxanthin from microbial biomass

Microorganisms such as bacteria, microalgae and fungi, are natural and rich sources of several valuable bioactive antioxidant's compounds, including carotenoids. Among the carotenoids with antioxidant properties, astaxanthin can be highlighted due to its pharmaceutical, feed, food, cosmetic and biotechnological applications. The best-known producers of astaxanthin are yeast and microalgae cells that biosynthesize this pigment intracellularly, requiring efficient and sustainable downstream procedures for its recovery. Conventional multi-step procedures usually involve the consumption of large amounts of volatile organic compounds (VOCs), which are regarded as toxic and hazardous chemicals. Considering these environmental issues, this review is focused on revealing the potential of unconventional extraction procedures [viz., Supercritical Fluid Extraction (SFE), Ultrasound-Assisted Extraction (UAE), Microwave-Assisted Extraction (MAE), High-Pressure Homogenization (HPH)] combined with alternative green solvents (biosolvents, eutectic solvents and ionic liquids) for the recovery of microbial-based astaxanthin from microalgae (such as Haematococcus pluvialis) and yeast (such as Phaffia rhodozyma) cells. The principal advances in the area, process bottlenecks, solvent selection and strategies to improve the recovery of microbial astaxanthin are emphasized. The promising recovery yields using these environmentally friendly procedures in lab-scale are good indications and directions for their effective use in biotechnological processes for the production of commercial feed and food ingredients like astaxanthin.

Cell disruption and astaxanthin extraction from Haematococcus pluvialis: Recent advances

The green microalga Haematococcus pluvialis is an excellent source of astaxanthin, a powerful antioxidant widely used in cosmetics, aquaculture, health foods, and pharmaceuticals. This review explores recent developments in cell disruption and astaxanthin extraction techniques applied using H. pluvialis as a model species for large-scale algal biorefinery. Notably, this alga develops a unique cyst-like cell with a rigid three-layered cell wall during astaxanthin accumulation (∼4% of dry weight) under stress. The thick (∼2 µm), acetolysis-resistant cell wall forms the strongest barrier to astaxanthin extraction. Various physical, chemical, and biological cell disruption methods were discussed and compared based on theoretical mechanisms, biomass status (wet, dry, and live), cell-disruption efficacy, astaxanthin extractability, cost, scalability, synergistic combinations, and impact on the stress-sensitive astaxanthin content. The challenges and future prospects of the downstream processes for the sustainable and economic development of advanced H. pluvialis biorefineries are also outlined.

Dietary natural products as a potential inhibitor towards advanced glycation end products and hyperglycemic complications: A phytotherapy approaches

Natural products exist in various natural foods such as plants, herbs, fruits, and vegetables. Furthermore, marine life offers potential natural products with significant biological activity. The biochemical reaction is known as advanced glycation end products (AGEs) occurs in the human body. On the other hand, foods are capable of a wide range of processing conditions resulting in the generation of exogenous AGEs adducts. Protein glycation and the formation of advanced glycation end products both contribute to the pathogenesis of hyperglycemic complications. AGEs also play a pivotal role in microvascular and macrovascular complications progression by receptors for advanced glycation end products (RAGE). RAGE activate by AGEs leads to up-regulation of transcriptional factor NF-kB and inflammatory genes. Around the globe, researchers are working in various approaches for therapeutical implications on controlling AGEs mediated disease complications. In this regard, one of the potential promising agents observed with a wide range of AGEs inhibition by food-derived natural products. Current biotechnological tools have been turned to natural products or phytochemicals to manufacture the molecules without compromising their functionality. Metabolic engineering and bioinformatics perspectives have recently enabled the generation of a few potent metabolites with anti-diabetic activity. As the primary focus, this review article will also discuss multidisciplinary approaches that emphasize current advances in anti-diabetic therapeutic action and future perspectives of natural products.

Microalgae for high-value products: A way towards green nutraceutical and pharmaceutical compounds

Microalgae is a renewable bioresource with the potential to replace the conventional fossil-based industrial production of organic chemicals and pharmaceuticals. Moreover, the microalgal biomass contains carotenoids, vitamins, and other biomolecules that are widely used as food supplements. However, the microalgal biomass production, their composition variations, energy-intensive harvesting methods, optimized bio-refinery routes, and lack of techno-economic analysis are the major bottleneck for the life-sized commercialization of this nascent bio-industry. This review discusses the microalgae-derived key bioactive compounds and their applications in different sectors for human health. Furthermore, this review proposes advanced strategies to enhance the productivity of bioactive compounds and highlight the key challenges associated with a safety issue for use of microalgae biomass. It also provides a detailed global scenario and market demand of microalgal bioproducts. In conclusion, this review will provide the concept of microalgal biorefinery to produce bioactive compounds at industrial scale platform for their application in the nutraceutical and pharmaceutical sector considering their current and future market trends.

Extraction of Antioxidant Compounds and Pigments from Spirulina (Arthrospira platensis) Assisted by Pulsed Electric Fields and the Binary Mixture of Organic Solvents and Water

The application of pulsed electric fields (PEF) is an innovative extraction technology promoting cell membrane electroporation, thus allowing for an efficient recovery, from an energy point of view, of antioxidant compounds (chlorophylls, carotenoids, total phenolic compounds, etc.) from microalgae. Due to its selectivity and high extraction yield, the effects of PEF pre-treatment (3 kV/cm, 100 kJ/kg) combined with supplementary extraction at different times (5–180 min) and with different solvents (ethanol (EtOH)/H2O, 50:50, v/v; dimethyl sulfoxide (DMSO)/H2O, 50:50, v/v) were evaluated in order to obtain the optimal conditions for the extraction of different antioxidant compounds and pigments. In addition, the results obtained were compared with those of a conventional treatment (without PEF pre-treatment but with constant shaking). After carrying out the different experiments, the best extraction conditions to recover the different compounds were obtained after applying PEF pre-treatment combined with the binary mixture EtOH/H2O, 50:50, v/v, for 60–120 min. PEF extraction was more efficient throughout the study, especially at short extraction times (5–15 min). In this sense, recovery of 55–60%, 85–90%, and 60–70% was obtained for chlorophylls, carotenoids, and total phenolic compounds, respectively, compared to the maximum total extracted amount. These results show that PEF improves the extraction yield of antioxidant bioactive compounds from microalgae and is a promising technology due to its profitability and environmental sustainability.

Microencapsulation of carotenoid-rich materials: A review

Carotenoids are natural pigments that present several bioactive properties, including antioxidant, anticarcinogenic and provitamin A activities. However, these compounds are susceptible to degradation when exposed to a number of conditions (e.g. light, heat, oxygen), leading to loss of benefits and hampering their application in food products. Their hydrophobicity also makes incorporation into water-based foods more difficult. Microencapsulation techniques have been applied for decades to provide stability to carotenoid-rich extracts under typical conditions of processing and storage of foods, besides offering several other advantages to the use and application of these materials. This work reviews the recent advances in the microencapsulation of carotenoid-rich extracts, oils and oleoresins from varying sources, evidencing the technologies applied to encapsulate these materials, the effects of encapsulation on the obtained particles, and the impact of such processes on the bioaccessibility and release profile of carotenoids from microparticles. Moreover, recent applications of carotenoid-rich microparticles in food products are discussed. Most of the applied processes were effective in improving different aspects of the encapsulated materials, especially the stability of carotenoids during storage, resulting in microparticles with promising properties for future applications in food products. However, the lack of information about the effects of microencapsulation on carotenoids during processing of model foods, the sensory acceptance of enriched food products and the bioaccessibility and bioavailability of microencapsulated carotenoids reveals gaps that should be explored in the future.

Effects of astaxanthin in animal models of obesity-associated diseases: A systematic review and meta-analysis

BACKGROUND AND AIM

Obesity is a major risk factor for several diseases, including metabolic syndrome (MetS), non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). The use of natural products, such as astaxanthin (ASX), a potent antioxidant compound produced by the freshwater green microalga Haematococcus pluvialis, has gained particular interest to reduce oxidative stress and inflammation, and to improve redox status, often associated with obesity. A systematic review and meta-analysis was performed to comprehensively examine the effects of ASX in animal models of diet induced obesity-associated diseases in order to inform the design of future human clinical studies for ASX use as supplement or nutraceutical.

METHODS

Cinahl, Cochraine, MEDLINE, Scopus and Web of Science were searched for English-language manuscripts published between January 2000 and April 2020 using the following key words: astaxanthin, obesity, non-alcoholic fatty liver disease, diabetes mellitus type 2, NAFLD and metabolic.

RESULTS

Seventeen eligible articles, corresponding to 21 animal studies, were included in the final quantitative analysis. ASX, at different concentrations and administered for different length of time, induced a significant reduction in adipose tissue weight (P = 0.05) and systolic blood pressure (P < 0.0001) in control animals. In animal models of T2D, ASX significantly reduced serum glucose levels (P = 0.04); whereas it improved several disease biomarkers in the blood (e.g. cholesterol, triglycerides, ALT and AST, P < 0.10), and reduced liver (P = 0.0002) and body weight (P = 0.11), in animal models of NAFLD.

CONCLUSIONS

Supplementation of ASX in the diet has positive effects on symptoms associated with obesity related diseases in animals, by having lipid-lowering, hypo-insulin and hypoglycaemic capacity, protecting organs from oxidative stress and mitigating the immune system, as suggested in this review.

An innovative protocol to select the best growth phase for astaxanthin biosynthesis in H. pluvialis

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H. pluvialis non-motile cells produce more astaxanthin.

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H. pluvialis cells could be separated, based on their size, by an electric field.

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H. pluvialis non-motile cells are bigger than motile cells, and it's possible to recovery non-motile cells using this innovative protocol.

H. pluvialis is a green unicellular microalgae and it is the first producer of natural astaxanthin in the world if subjected to stress conditions such as high light, high salinity and nutrient starvation. Astaxanthin is a powerful antioxidant used in many fields, such as aquaculture, pharmaceutical, food supplements and cosmetic. To obtain a large amount of astaxanthin, researcher focused on the optimisation of H. pluvialis growth. H. pluvialis has four different size growth stage (macrozooids, microzooids, palmelloid and “red non-motile astaxanthin accumulated encysted”), and astaxanthin production occur in the last phase. Recent studies shown that non-motile cells can produce more astaxanthin than motile cells if subjected to light stress. For these reasons, the aim of this study is to find a new and innovative methodology to select and recovery H. pluvialis in his last growth phase thanks to an electrophoretic run, and optimize, in this way, astaxanthin production.

Extraction of Pigments from Microalgae and Cyanobacteria—A Review on Current Methodologies

Pigments from microalgae and cyanobacteria have attracted great interest for industrial applications due to their bioactive potential and their natural product attributes. These pigments are usually sold as extracts, to overcome purification costs. The extraction of these compounds is based on cell disruption methodologies and chemical solubility of compounds. Different cell disruption methodologies have been used for pigment extraction, such as sonication, homogenization, high-pressure, CO2 supercritical fluid extraction, enzymatic extraction, and some other promising extraction methodologies such as ohmic heating and electric pulse technologies. The biggest constrain on pigment bioprocessing comes from the installation and operation costs; thus, fundamental and applied research are still needed to overcome such constrains and give the microalgae and cyanobacteria industry an opportunity in the world market. In this review, the main extraction methodologies will be discussed, taking into account the advantages and disadvantages for each kind of pigment, type of organism, cost, and final market.

Technological Applications of Natural Colorants in Food Systems: A Review

Natural colorants have emerged as an alternative to their synthetic counterparts due to an existing health concern of these later. Moreover, natural-food colorants are a renewable option providing health benefits and interesting technological and sensory attributes to the food systems containing them. Several sources of natural colorants have been explored aiming to deliver the required wide color range demanded by consumers. This review aimed to compare and discuss the technological applications of the main natural-food colorants into food system in the last six years, giving additional information about their extraction process. Although natural colorants are promising choices to replace synthetic ones, optimization of processing conditions, research on new sources, and new formulations to ensure stability are required to equate their properties to their synthetic counterparts.

Effect of dietary astaxanthin administration on the growth performance and innate immunity of juvenile crucian carp (Carassius auratus)

The present study aims to explore the effects of oral astaxanthin administration on the growth performance and innate immunity of juvenile crucian carp (Carassius auratus). Juvenile crucian carps with a bodyweight of 40.06 ± 2.17 g were randomly assigned to four groups, i.e., one control group fed with a basic diet and three treatment groups fed with a diet that contains 200, 400 and 800 mg/kg astaxanthin. After 60 days of feeding, the groups fed with astaxanthin-containing diets had improved body weight gain rate; feed conversion ratio; intestinal digestive protease, lipase and amylase levels; serum superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase and lysozyme activities; complement 3 and complement 4 levels; interleukin (IL)-10 and resistance to Aeromonas hydrophilia and reduced serum aspartate aminotransferase and alanine aminotransferase activities and tumour necrosis factor-α, IL-1β and IL-8 levels compared with those of the control group. Based on the efficiency of the oral administration of astaxanthin on the growth performance of juvenile crucian carps, the optimum dose of astaxanthin was 400 mg/kg. Results indicated that astaxanthin may be used as a dietary supplement for the crucian carp.

Importance of Downstream Processing of Natural Astaxanthin for Pharmaceutical Application

Astaxanthin (ASX) is a xanthophyll pigment considered as a nutraceutical with high antioxidant activity. Several clinical trials have shown the multiple health benefits of this molecule; therefore, it has various pharmaceutical industry applications. Commercial astaxanthin can be produced by chemical synthesis or through biosynthesis within different microorganisms. The molecule produced by the microorganisms is highly preferred due to its zero toxicity and superior therapeutic properties. However, the biotechnological production of the xanthophyll is not competitive against the chemical synthesis, since the downstream process may represent 70–80% of the process production cost. These operations denote then an opportunity to optimize the process and make this alternative more competitive. Since ASX is produced intracellularly by the microorganisms, high investment and high operational costs, like centrifugation and bead milling or high-pressure homogenization, are mainly used. In cell recovery, flocculation and flotation may represent low energy demanding techniques, whereas, after cell disruption, an efficient extraction technique is necessary to extract the highest percentage of ASX produced by the cell. Solvent extraction is the traditional method, but large-scale ASX production has adopted supercritical CO2 (SC-CO2), an efficient and environmentally friendly technology. On the other hand, assisted technologies are extensively reported since the cell disruption, and ASX extraction can be carried out in a single step. Because a high-purity product is required in pharmaceuticals and nutraceutical applications, the use of chromatography is necessary for the downstream process. Traditionally liquid-solid chromatography techniques are applied; however, the recent emergence of liquid-liquid chromatography like high-speed countercurrent chromatography (HSCCC) coupled with liquid-solid chromatography allows high productivity and purity up to 99% of ASX. Additionally, the use of SC-CO2, coupled with two-dimensional chromatography, is very promising. Finally, the purified ASX needs to be formulated to ensure its stability and bioavailability; thus, encapsulation is widely employed. In this review, we focus on the processes of cell recovery, cell disruption, drying, extraction, purification, and formulation of ASX mainly produced in Haematococcus pluvialis, Phaffia rhodozyma, and Paracoccus carotinifaciens. We discuss the current technologies that are being developed to make downstream operations more efficient and competitive in the biotechnological production process of this carotenoid.

Replacing fish oil and astaxanthin by microalgal sources produced different metabolic responses in juvenile rainbow trout fed 2 types of practical diets

Dietary fish oil supplementation provides n-3 long-chained polyunsaturated fatty acids for supporting fish growth and metabolism and enriching fillet with eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; c22:6n-3). Two experiments were performed as a 3 × 2 factorial arrangement of dietary treatments for 16 wk to determine effects and mechanisms of replacing 0%, 50%, and 100% fish oil with DHA-rich microalgae in combination with synthetic vs. microalgal source of astaxanthin in plant protein meal (PM)- or fishmeal (FM)- based diets for juvenile rainbow trout (Oncorhynchus mykiss). Fish (22 ± 0.26 g) were stocked at 17/tank and 3 tanks/diet. The 100% fish oil replacement impaired (P < 0.0001) growth performance, dietary protein and energy utilization, body indices, and tissue accumulation of DHA and EPA in both diet series. The impairments were associated (P < 0.05) with upregulation of hepatic gene expression related to growth (ghr1and igf1) and biosynthesis of DHA and EPA (fads6 and evol5) that was more dramatic in the FM than PM diet-fed fish, and more pronounced on tissue EPA than DHA concentrations. The source of astaxanthin exerted interaction effects with the fish oil replacement on several measures including muscle total cholesterol concentrations. In conclusion, replacing fish oil by the DHA-rich microalgae produced more negative metabolic responses than the substitution of synthetic astaxanthin by the microalgal source in juvenile rainbow trout fed 2 types of practical diets.

Microalgae Biomolecules: Extraction, Separation and Purification Methods

Several microalgae species have been exploited due to their great biotechnological potential for the production of a range of biomolecules that can be applied in a large variety of industrial sectors. However, the major challenge of biotechnological processes is to make them economically viable, through the production of commercially valuable compounds. Most of these compounds are accumulated inside the cells, requiring efficient technologies for their extraction, recovery and purification. Recent improvements approaching physicochemical treatments (e.g., supercritical fluid extraction, ultrasound-assisted extraction, pulsed electric fields, among others) and processes without solvents are seeking to establish sustainable and scalable technologies to obtain target products from microalgae with high efficiency and purity. This article reviews the currently available approaches reported in literature, highlighting some examples covering recent granted patents for the microalgae’s components extraction, recovery and purification, at small and large scales, in accordance with the worldwide trend of transition to bio-based products.

Astaxanthin improves serum cytokine expression and semen quality of diabetes mellitus KKAy mice

The present study aims to explore the effects of astaxanthin on the semen quality of diabetes mellitus (DM) KKAy mice. A total of 60 DM KKAy mice with similar body weights and initial blood glucose and serum lipid levels were assigned to four groups, namely, one control and three astaxanthin treatments (10, 50, or 100 mg/kg astaxanthin). Results show that oral astaxanthin administration reduced fasting blood glucose and serum total cholesterol, low-density lipoprotein cholesterol, insulin and nitrate oxide levels in the testis of DM KKAy mice. Astaxanthin also improved the high-density lipoprotein cholesterol, protein and superoxide dismutase levels in the testis; serum interleukin-11, tumour necrosis factor-α and interferon-γ levels; and sperm density, sperm movement and normal morphology rate of DM KKAy mice. Based on the results, astaxanthin can effectively affect serum cytokines and ameliorate semen quality of DM KKAy mice; thus, it may be developed as an adjuvant drug to treat diabetes mellitus-induced infertility.

Current and novel approaches to downstream processing of microalgae: A review

Biotechnological application of microalgae cultures at large scale has significant potential in the various fields of biofuels, food and feed, cosmetic, pharmaceutic, environmental remediation and water treatment. Despite this great potential application, industrialisation of microalgae culture and valorisation is still faced with serious remaining challenges in culture scale-up, harvesting and extraction of target molecules. This review presents a general summary of current techniques for harvesting and extraction of biomolecules from microalgae, their relative merits and potential for industrial application. The cell wall composition and its impact on microalgae cell disruption is discussed. Additionally, more recent progress and promising experimental methods and studies are summarised that would allow the reader to further investigate the state of the art. A final survey of energetic assessments of the different techniques is also made. Bead milling and high-pressure homogenisation seem to give clear advantages in terms of target high value compounds extraction from microalgae, with enzyme hydrolysis as a promising emerging technique. Future industrialisation of microalgae for high scale biotechnological processing will require the establishment of universal comparison-standards that would enable easy assessment of one technique against another.

Enzymatic Processes Triggered by PEF for Astaxanthin Extraction From Xanthophyllomyces dendrorhous

The aim of this study was to evaluate the potential of pulsed electric fields (PEF) to improve the extraction of the lipid-soluble astaxanthin from fresh biomass of a wild-type (CECT 11028) and mutant (ATCC 74219) Xanthophyllomyces dendrorhous strain using ethanol as solvent. Inactivation and propidium uptake studies revealed that inactivation is a good index for estimated the proportion of irreversible permeabilized cells when inactivation is higher than 70% in the two strains. Ethanol was ineffective for extracting carotenoids from the PEF-treated cells (20 kV/cm, 135 μs) of the two strains. However, after aqueous incubation of PEF-treated X. dendrorhous ATCC 74219 cells for 12 h, up to 2.4 ± 0.05 mg/g dried weight (d.w.) of carotenoids were extracted in ethanol. From total carotenoid extracted, around 84% corresponded to all-trans astaxanthin. The detection and quantification of esterase activity in the supernatant and the relationship between the percentage of esterase activity quantified and the amount of carotenoids extracted indicate that the extraction of astaxanthin was mediated by enzymatic esterase activity triggered by PEF during incubation. On the other hand, the formation of a large lipid globule into the cytoplasm of PEF-treated X. dendrorhous CECT 11028 cells during aqueous incubation prevented carotenoid extraction. The process developed in this investigation represents a more sustainable and greener method that those previously used for extracting astaxanthin from yeast.

Improved Extraction Efficiency of Antioxidant Bioactive Compounds from Tetraselmis chuii and Phaedoactylum tricornutum Using Pulsed Electric Fields

Pulsed electric fields (PEF) is a promising technology that allows the selective extraction of high-added value compounds by electroporation. Thus, PEF provides numerous opportunities for the energy efficient isolation of valuable microalgal bioactive substances (i.e., pigments and polyphenols). The efficiency of PEF-assisted extraction combined with aqueous or dimethyl sulfoxide (DMSO) solvents in recovering pigments and polyphenols from microalgae Tetraselmis chuii (T. chuii) and Phaeodactylum tricornutum (P. tricornutum) was evaluated. Two PEF treatments were applied: (1 kV/cm/400 pulses, 3 kV/cm/45 pulses), with a specific energy input of 100 kJ/kg. The total antioxidant capacity (TAC) was positively influenced by the use of DMSO. The highest TAC in the T. chuii culture was achieved at a lower extraction time and electric field than for P. tricornutum. The use of DMSO only improved the polyphenols' extraction for P. tricornutum, whereas the PEF and extraction time were more important for T. chuii. Carotenoids and chlorophyll a were more efficiently extracted using DMSO, while chlorophyll b levels were higher following aqueous extraction for both microalgae. In P. tricornutum, the TAC and pigment extraction efficiency were in general higher at lower extraction times. It can be concluded that PEF may be a promising alternative for the enhancement of the selective extraction of antioxidant bioactive compounds from microalgae.

Progress in the physicochemical treatment of microalgae biomass for value-added product recovery

Interest in microalgae-derived products is growing, mostly due to their unique characteristics and range of industrial applications. To obtain different products, one must employ specific pretreatments that retain the properties of the biologically active compounds extracted from microalgae biomass; thus, new extraction techniques require frequent upgrades. Due to increased interest in economically viable and ecologically friendly processes, new extraction methods that can be incorporated into microalgae biorefinery systems have become the main focus of research. Therefore, this review aims to address the potential applications, future prospects, and economic scenario of the new physicochemical treatments used in the extraction of bioactive microalgae compounds.

Pulsed electric field-assisted extraction of valuable compounds from microorganisms

Microorganisms (bacteria, yeast, and microalgae) are a promising resource for products of high value such as nutrients, pigments, and enzymes. The majority of these compounds of interest remain inside the cell, thus making it necessary to extract and purify them before use. This review presents the challenges and opportunities in the production of these compounds, the microbial structure and the location of target compounds in the cells, the different procedures proposed for improving extraction of these compounds, and pulsed electric field (PEF)-assisted extraction as alternative to these procedures. PEF is a nonthermal technology that produces a precise action on the cytoplasmic membrane improving the selective release of intracellular compounds while avoiding undesirable consequences of heating on the characteristics and purity of the extracts. PEF pretreatment with low energetic requirements allows for high extraction yields. However, PEF parameters should be tailored to each microbial cell, according to their structure, size, and other factors affecting efficiency. Furthermore, the recent discovery of the triggering effect of enzymatic activity during cell incubation after electroporation opens up the possibility of new implementations of PEF for the recovery of compounds that are bounded or assembled in structures. Similarly, PEF parameters and suspension storage conditions need to be optimized to reach the desired effect. PEF can be applied in continuous flow and is adaptable to industrial equipment, making it feasible for scale-up to large processing capacities.

Statistical Methods for Rapid Quantification of Proteins, Lipids, and Carbohydrates in Nordic Microalgal Species Using ATR-FTIR Spectroscopy

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy is a simple, cheap, and fast method to collect chemical compositional information from microalgae. However, (semi)quantitative evaluation of the collected data can be daunting. In this work, ATR-FTIR spectroscopy was used to monitor changes of protein, lipid, and carbohydrate content in seven green microalgae grown under nitrogen starvation. Three statistical methods-univariate linear regression analysis (ULRA), orthogonal partial least squares (OPLS), and multivariate curve resolution-alternating least squares (MCR-ALS)-were compared in their ability to model and predict the concentration of these compounds in the biomass. OPLS was found superior, since it i) included all three compounds simultaneously; ii) explained variations in the data very well; iii) had excellent prediction accuracy for proteins and lipids, and acceptable for carbohydrates; and iv) was able to discriminate samples based on cultivation stage and type of storage compounds accumulated in the cells. ULRA models worked well for the determination of proteins and lipids, but carbohydrates could only be estimated if already determined protein contents were used for scaling. Results obtained by MCR-ALS were similar to ULRA, however, this method is considerably easier to perform and interpret than the more abstract statistical/chemometric methods. FTIR-spectroscopy-based models allow high-throughput, cost-effective, and rapid estimation of biomass composition of green microalgae.