Recovery of Astaxanthin-Containing Oil from Haematococcus pluvialis by Nano-dispersion and Oil Partitioning

Advancement of Carotenogenesis of Astaxanthin from Haematococcus pluvialis: Recent Insight and Way Forward

The demand for astaxanthin has been increasing for many health applications ranging from pharmaceuticals, food, cosmetics, and aquaculture due to its bioactive properties. Haematococcus pluvialis is widely recognized as the microalgae species with the highest natural accumulation of astaxanthin, which has made it a valuable source for industrial production. Astaxanthin produced by other sources such as chemical synthesis or fermentation are often produced in the cis configuration, which has been shown to have lower bioactivity. Additionally, some sources of astaxanthin, such as shrimp, may denature or degrade when exposed to high temperatures, which can result in a loss of bioactivity. Producing natural astaxanthin through the cultivation of H. pluvialis is presently a demanding and time-consuming task, which incurs high expenses and restricts the cost-effective industrial production of this valuable substance. The production of astaxanthin occurs through two distinct pathways, namely the cytosolic mevalonate pathway and the chloroplast methylerythritol phosphate (MEP) pathway. The latest advancements in enhancing product quality and extracting techniques at a reasonable cost are emphasized in this review. The comparative of specific extraction processes of H. pluvialis biological astaxanthin production that may be applied to large-scale industries were assessed. The article covers a contemporary approach to optimizing microalgae culture for increased astaxanthin content, as well as obtaining preliminary data on the sustainability of astaxanthin production and astaxanthin marketing information.

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.

Developing industry-scale microfluidization for cell disruption, biomolecules release and bioaccessibility improvement of Chlorella pyrenoidosa

To facilitate biomolecules extraction and bioaccessibility of Chlorella pyrenoidosa, a novel industry-scale microfluidization (ISM) was used to disrupt cells effectively. Microscope images showed ISM damaged cell integrity, disorganized cell wall structure, pulverized cell membrane and promoted the release of intracellular components. The decrease of particle size and the increase of ζ-potential also confirmed the cell disruption. The cell breakage ratio of sample treated at 120 MPa was 98%. Compared with untreated samples, total soluble solid content and protein extraction rate of the sample treated at 120 MPa increased by 2 °Brix and 12%. Protein was degraded by ISM, the release of intracellular protein and the reduction of molecular weight increased protein digestibility by 20% in in vitro gastric phase. Lipid yield and chlorophyll b content were also increased by ISM. These results provided a new solution to cell disruption of microalgae and expanded the application field of ISM.

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.

Comparative study on photosynthetic and antioxidant activities of Haematococcus pluvialis vegetative and resting cells; UVA light-induced stimulation

AIM

This study aims to determine how photosynthetic and antioxidant activities vary in vegetative and dormant cells of Haematococcus pluvialis subjected to stresses in conditions representative of industrial productions of microalgae under solar light.

METHODS AND RESULTS

The effects of short-term oxidative treatments were examined on photosynthetic and antioxidant activities of Haematococcus pluvialis vegetative and resting cells. The vegetative cells have 1.6 times higher levels of phenolic compounds, but 1.7 times less catalase, ascorbate peroxidase, and superoxide dismutase activities than the astaxanthin-enriched resting cells. Mainly, a UVA dose of 4 J cm^-2 induced increases in photosystem II electron transport rates (ETRmax) (+15%), phenolic compounds (+15%), astaxanthin (+ 48%), catalase (+45%), and superoxide dismutase (+30%) activities in vegetative cells.

CONCLUSION

The UVA-dose strongly stimulates the photosynthetic and antioxidant activities of vegetative cells, but only the accumulation of astaxanthin in resting cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

These preliminary results show that oxidative stresses at sub-lethal levels can stimulate the activities of microalgae. Further investigations are needed to estimate the real influence on metabolite productivities in industrial production conditions.

Room-Temperature Cell Disruption and Astaxanthin Recovery from Haematococcus lacustris Cysts Using Ultrathin α-Quartz Nanoplates and Ionic Liquids

Ionic liquids (ILs) are new green solvents, which are widely used in lignocellulosic and microalgal biorefineries. However, high-temperature operating conditions limit their application in the extraction of heat-labile algal products, such as bioactive astaxanthin. In this study, we report the technical feasibility of room-temperature astaxanthin extraction from Haematococcus lacustris cysts with a thick and complex cell wall structure, by combining ultrathin α-quartz nanoplates (NPLs) with ethyl-3-methylimidazolium ([Emim])-based ILs. When four different [Emim]-based ILs with thiocyanate (SCN), diethylphosphate (DEP), HSO4, and Cl anions were applied to 90-day-old H. lacustris cysts at room temperature (~28 °C), the astaxanthin extraction efficiency was as low as 9.6–14.2%. Under sonication, α-quartz NPLs disrupted the cyst cell wall for a short duration (5 min). The astaxanthin extraction efficacies of a subsequent IL treatment improved significantly to 49.8% for [Emim] SCN, 60.0% for [Emim] DEP, 80.7% for [Emim] HSO4, and 74.3% for [Emim] Cl ions, which were 4.4, 6.1, 8.4, and 5.2 times higher than the extraction efficacy of only ILs, respectively. This finding suggests that α-quartz NPLs can serve as powerful cell-wall-disrupting agents for the room-temperature IL-mediated extraction of astaxanthin from robust algal cyst cells.

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.

A Method of Solubilizing and Concentrating Astaxanthin and Other Carotenoids

The valuable marine carotenoid, astaxanthin, is used in supplements, medicines and cosmetics. In this study, crustacyanin, an astaxanthin-binding protein, was used to solubilize and concentrate astaxanthin. The recombinant crustacyanin of European lobster spontaneously formed an inclusion body when it was over-expressed in Escherichia coli. In this study, fusing the NusA-tag to the crustacyanin subunits made it possible to express in a soluble fraction and solubilize astaxanthin in aqueous solution. By cutting off the NusA-tag, the crustacyanin subunits generated the pure insoluble form, and captured and concentrated astaxanthin. Overall, the attaching and releasing NusA-tag method has the potential to supply solubilized carotenoids in aqueous solution and concentrated carotenoids, respectively.

Morphological Change and Cell Disruption of Haematococcus pluvialis Cyst during High-Pressure Homogenization for Astaxanthin Recovery

Haematococcus pluvialis accumulates astaxanthin, which is a high-value antioxidant, during the red cyst stage of its lifecycle. The development of a rigid cell wall in the cysts hinders the recovery of astaxanthin. We investigated morphological changes and cell disruption of mature H. pluvialis cyst cells while using high-pressure homogenization for astaxanthin extraction. When treated with French-press-cell (pressure, 10,000–30,000 psi; passage, 1–3), the intact cyst cells were significantly broken or fully ruptured, releasing cytoplasmic components, thereby facilitating the separation of astaxanthin by ethyl acetate. Fluorescence microscopy observations using three different fluorescent dyes revealed that a greater degree of cell breakage caused greater external dispersion of astaxanthin, chlorophyll, lipids, proteins, and carbohydrates. The mechanical treatment resulted in a high cell disruption rate of up to 91% based on microscopic cell typing and Coulter methods. After the ethyl acetate extraction, the astaxanthin concentration significantly increased by 15.2 mg/L in proportion to the increase in cell disruption rate, which indicates that cell disruption is a critical factor for solvent-based astaxanthin recovery. Furthermore, this study recommends a synergistic combination of the fast instrumental particle-volume-distribution analysis and microscope-based morphologic phenotyping for the development of practical H. pluvialis biorefinery processes that co-produce various biological products, including lipids, proteins, carbohydrates, chlorophyll, and astaxanthin.