Advances and trends in biotechnological production of natural astaxanthin by Phaffia rhodozyma yeast

Astaxanthin biosynthesis for functional food development and space missions

Astaxanthin (AXT), a natural carotenoid, has strong antioxidant and anti-ageing effects and can reduce ultraviolet light-induced damage to cells and DNA, stimulate the immune system, and improve cardiovascular disease prognosis. Despite its wide applications in the: nutraceutical, cosmetic, aquaculture, and pharmaceutical industries, AXT industrial production and application are hindered by natural source scarcity, low production efficiency, and high requirements. This review compares the qualitative differences of AXT derived from different natural sources, evaluates the upstream procedures for AXT expression in different chassis organisms, and investigates synthetic biology- and cell factory-based strategies for the industrial production of natural AXT. Synthetic biology is a promising novel strategy for reprogramming plants or microorganisms to produce AXT. Additionally, genetic engineering using cell factories extends beyond terrestrial applications, as it may contribute to the long-term sustainability of human health during space exploration and migration endeavors. This review provides a theoretical basis for the efficient and accurate genetic engineering of AXT from the microalga Haematococcuspluvialis, providing a valuable reference for future research on the biomanufacturing of AXT and other biological metabolites.

Advancements of astaxanthin production in Haematococcus pluvialis: Update insight and way forward

The global market demand for natural astaxanthin (AXT) is growing rapidly owing to its potential human health benefits and diverse industry applications, driven by its safety, unique structure, and special function. Currently, the alga Haematococcus pluvialis (alternative name H. lacustris) has been considered as one of the best large-scale producers of natural AXT. However, the industry's further development faces two main challenges: the limited cultivation areas due to light-dependent AXT accumulation and the low AXT yield coupled with high production costs resulting from complex, time-consuming upstream biomass culture and downstream AXT extraction processes. Therefore, it is urgently to develop novel strategies to improve the AXT production in H. pluvialis to meet industrial demands, which makes its commercialization cost-effective. Although several strategies related to screening excellent target strains, optimizing culture condition for high biomass yield, elucidating the AXT biosynthetic pathway, and exploiting effective inducers for high AXT content have been applied to enhance the AXT production in H. pluvialis, there are still some unsolved and easily ignored perspectives. In this review, firstly, we summarize the structure and function of natural AXT focus on those from the algal H. pluvialis. Secondly, the latest findings regarding the AXT biosynthetic pathway including spatiotemporal specificity, transport, esterification, and storage are updated. Thirdly, we systematically assess enhancement strategies on AXT yield. Fourthly, the regulation mechanisms of AXT accumulation under various stresses are discussed. Finally, the integrated and systematic solutions for improving AXT production are proposed. This review not only fills the existing gap about the AXT accumulation, but also points the way forward for AXT production in H. pluvialis.

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.

Biotechnological approaches for producing natural pigments in yeasts

Pigments are widely used in the food, cosmetic, textile, pharmaceutical, and materials industries. Demand for natural pigments has been increasing due to concerns regarding potential health problems and environmental pollution from synthetic pigments. Microbial production of natural pigments is a promising alternative to chemical synthesis or extraction from natural sources. Here, we discuss yeasts as promising chassis for producing natural pigments with their advantageous traits such as genetic amenability, safety, rapid growth, metabolic diversity, and tolerance. Metabolic engineering strategies and optimizing strategies in downstream process to enhance production of natural pigments are thoroughly reviewed. We discuss the challenges, including expanding the range of natural pigments and improving their feasibility of industrial scale-up, as well as the potential strategies for future development.

Industrial Production of Functional Foods for Human Health and Sustainability

Functional foods significantly affect social stability, human health, and food security. Plants and microorganisms are high-quality chassis for the bioactive ingredients in functional foods. Characterised by precise nutrition and the provision of both nutritive and medicinal value, functional foods serve a as key extension of functional agriculture and offer assurance of food availability for future space exploration efforts. This review summarises the main bioactive ingredients in functional foods and their functions, describes the strategies used for the nutritional fortification and industrial production of functional foods, and provides insights into the challenges and future developments in the applications of plants and microorganisms in functional foods. Our review aims to provide a theoretical basis for the development of functional foods, ensure the successful production of new products, and support the U.N. Sustainable Development Goals, including no poverty, zero hunger, and good health and well-being.

The Application of Fungi and Their Secondary Metabolites in Aquaculture

Ensuring sustainability has increasingly become a significant concern not only in aquaculture but in the general agrifood sector. Therefore, it is imperative to investigate pathways to feed substitutes/best practices to enhance aquaculture sustainability. The application of fungi in aquaculture provides innovative methods to enhance the sustainability and productivity of aquaculture. Fungi play numerous roles in aquaculture, including growth, immunity enhancement and disease resistance. They also play a role in bioremediation of waste and bioflocculation. The application of fungi improves the suitability and utilization of terrestrial plant ingredients in aquaculture by reducing the fibre fractions and anti-nutritional factors and increasing the nutrients and mineral contents of plant ingredients. Fungi are good flotation agents and can enhance the buoyancy of aquafeed. Pigments from fungi enhance the colouration of fish fillets, making them more attractive to consumers. This paper, via the relevant literature, explores the multifaceted roles of fungi in aquaculture, emphasizing their potential to transform aquaculture through environmentally friendly and sustainable techniques. The effectiveness of fungi in reducing fibre fractions and enhancing nutrient availability is influenced by the duration of fermentation and the dosage administered, which may differ for various feed ingredients, making it difficult for most aquaculture farmers to apply fungi approximately. Therefore, the most effective dosage and fermentation duration for each feed ingredient should be investigated.

Biovalorisation of agro-industrial wastes into astaxanthin by Xanthophyllomyces dendrorhous

Astaxanthin is a red xanthophyll with high economic and industrial value in the pharmaceutical, nutraceutical, cosmetic and food industries. In recent years, the biotechnological production of astaxanthin has attracted much attention as a sustainable alternative to the predominating petrochemical-dependent chemical synthesis. In this regard, Xanthophyllomyces dendrorhous is regarded as a promising microorganism for industrial production of astaxanthin. Unfortunately, biotechnological production of the carotenoid is currently expensive. The present study investigated soy molasses (SM) and residual brewers' yeast as cheap fermentation feedstocks for the cultivation of X. dendrorhous and astaxanthin production. Yeast extract was obtained from residual brewers' yeast using various techniques and then combined with SM to formulate a two-component growth medium which was subsequently used to cultivate X. dendrorhous. Generally, the yeast extract produced from residual brewers' yeast supported X. dendrorhous growth and astaxanthin production at levels comparable to those seen with commercial yeast extract. Overall, cultivating X. dendrorhous in an SM-based medium containing 5% SM and 0.2% yeast extract obtained from residual brewers' yeast resulted in significantly higher (> 20% more) biomass accumulation compared to the control media (YPD). A similar slightly higher astaxanthin output (up to 14% more) was recorded in the SM-based medium compared to YPD. The formulated cultivation medium in this study provides an opportunity to reduce the production cost of astaxanthin from X. dendrorhous while simultaneously reducing the environmental impact related to the disposal of the industrial waste used as feedstock. KEY POINTS: • Cheap culture media were formulated from soy molasses and brewers' spent yeast • The formulated medium resulted in at least 20% more biomass than the control • Up to 14% more astaxanthin was produced in molasses-based medium.

Astaxanthin Isomers: A Comprehensive Review of Isomerization Methods and Analytic Techniques

The presence of multiple conjugated double bonds and chiral carbon atoms endows astaxanthin with geometric and optical isomers, and these isomers widely exist in biological sources, food processing, and in vivo absorption. However, there remains no systematic summary of astaxanthin isomers regarding isomerization methods and analytic techniques. To address this need, this Review focuses on a comprehensive analysis of Z-isomerization methods of astaxanthin, including solvent system, catalyst, and heat treatment. Comparatively, high-efficiency and health-friendly methods are more conducive to put into practical use, such as food-grade solvents and food-component catalysts. In addition, we outline the recent advances in analysis techniques of astaxanthin isomers, as well as the structural characteristics reflected by various methods (e.g., HPLC, NMR, FTIR, and RS). Furthermore, we summarized the related research on the safety evaluation of astaxanthin isomers. Finally, future trends and barriers in Z-transformation and analysis of astaxanthin isomers are also discussed.

Microbial astaxanthin: from bioprocessing to the market recognition

The attractive biological properties and health benefits of natural astaxanthin (AXT), including its antioxidant and anti-carcinogenic properties, have garnered significant attention from academia and industry seeking natural alternatives to synthetic products. AXT, a red ketocarotenoid, is mainly produced by yeast, microalgae, wild or genetically engineered bacteria. Unfortunately, the large fraction of AXT available in the global market is still obtained using non-environmentally friendly petrochemical-based products. Due to the consumers concerns about synthetic AXT, the market of microbial-AXT is expected to grow exponentially in succeeding years. This review provides a detailed discussion of AXT's bioprocessing technologies and applications as a natural alternative to synthetic counterparts. Additionally, we present, for the first time, a very comprehensive segmentation of the global AXT market and suggest research directions to improve microbial production using sustainable and environmentally friendly practices. KEY POINTS: • Unlock the power of microorganisms for high value AXT production. • Discover the secrets to cost-effective microbial AXT processing. • Uncover the future opportunities in the AXT market.

High-Purity Bioactive Ingredient—3S,3′S-Astaxanthin: A New Preparation from Genetically Modified Kluyveromyces marxianus without Column Chromatography and Gel Filtration

A highly efficient methodology for bioactive ingredient 3S,3′S-astaxanthin (3S,3′S-AST) preparation from genetically modified yeast (Kluyveromyces marxianus) with a combination of enzyme-assisted extraction and salt-assisted liquid-liquid extraction (SALLE) was achieved. The highest yield of 3S,3′S-AST indicated that FoodPro® CBL for yeast cell walls hydrolysis could significantly enhance extraction and obtain, with the help of SALLE procedure, quantified 3S,3′S-AST over 99% in purity through cation chelation. In the oxygen radical antioxidant capacity (ORAC) assay, the antioxidant capacity of high-purity 3S,3′S-AST products were 18.3 times higher than that of the original raw material extract. This new combination preparation may replace previous methods and has the potential to be scaled up in the manufacture of high-purity 3S,3′S-AST from low-value bioresources of raw materials to high-value products in the food and/or drug industries with lower cost and simple equipment.

An enhanced electron transport chain improved astaxanthin production in Phaffia rhodozyma

Astaxanthin (AX) is a carotenoid pigment with antioxidant properties widely used as a feed supplement. Wild-type strains of Phaffia rhodozyma naturally produce low AX yields, but we increased AX yields 50-fold in previous research using random mutagenesis of P. rhodozyma CBS6938 and fermentation optimization. On that study, genome changes were linked with phenotype, but relevant metabolic changes were not resolved. In this study, the wild-type and the superior P. rhodozyma mutant strains were grown in chemically defined media and instrumented fermenters. Differential kinetic, metabolomics, and transcriptomics data were collected. Our results suggest that carotenoid production was mainly associated with cell growth and had a positive regulation of central carbon metabolism metabolites, amino acids, and fatty acids. In the stationary phase, amino acids associated with the TCA cycle increased, but most of the fatty acids and central carbon metabolism metabolites decreased. TCA cycle metabolites were in abundance and media supplementation of citrate, malate, α-ketoglutarate, succinate, or fumarate increased AX production in the mutant strain. Transcriptomic data correlated with the metabolic and genomic data and found a positive regulation of genes associated with the electron transport chain suggesting this to be the main driver for improved AX production in the mutant strain.

Red yeasts and their carotenogenic enzymes for microbial carotenoid production

Carotenoids are C40 isoprene-based compounds with significant commercial interests that harbor diverse bioactivities. Prominent examples of carotenoids are beta-carotene, a precursor to vitamin A essential for proper eye health, and lycopene and astaxanthin, powerful antioxidants implicated in preventing cancers and atherosclerosis. Due to their benefits to human health, the market value for carotenoids is rapidly increasing and is projected to reach USD 1.7 billion by 2025. However, their production now relies on chemical synthesis and extraction from plants that pose risks to food management and numerous biological safety issues. Thus, carotenoid production from microbes is considered a promising strategy for achieving a healthy society with more sustainability. Red yeast is a heterogeneous group of basidiomycetous fungi capable of producing carotenoids. It is a critical source of microbial carotenoids from low-cost substrates. Carotenogenic enzymes from red yeasts have also been highly efficient, invaluable biological resources for biotechnological applications. In this minireview, we focus on red yeast as a promising source for microbial carotenoids, strain engineering strategies for improving carotenoid production in red yeasts, and potential applications of carotenogenic enzymes from red yeasts in conventional and nonconventional yeasts.

Development of Biotechnological Photosensitizers for Photodynamic Therapy: Cancer Research and Treatment-From Benchtop to Clinical Practice

Photodynamic therapy (PDT) is a noninvasive therapeutic approach that has been applied in studies for the treatment of various diseases. In this context, PDT has been suggested as a new therapy or adjuvant therapy to traditional cancer therapy. The mode of action of PDT consists of the generation of singlet oxygen (¹O₂) and reactive oxygen species (ROS) through the administration of a compound called photosensitizer (PS), a light source, and molecular oxygen (³O₂). This combination generates controlled photochemical reactions (photodynamic mechanisms) that produce ROS, such as singlet oxygen (¹O₂), which can induce apoptosis and/or cell death induced by necrosis, degeneration of the tumor vasculature, stimulation of the antitumor immune response, and induction of inflammatory reactions in the illuminated region. However, the traditional compounds used in PDT limit its application. In this context, compounds of biotechnological origin with photosensitizing activity in association with nanotechnology are being used in PDT, aiming at its application in several types of cancer but with less toxicity toward neighboring tissues and better absorption of light for more aggressive types of cancer. In this review, we present studies involving innovatively developed PS that aimed to improve the efficiency of PDT in cancer treatment. Specifically, we focused on the clinical translation and application of PS of natural origin on cancer.

GATA transcription factor WC2 regulates the biosynthesis of astaxanthin in yeast Xanthophyllomyces dendrorhous

Astaxanthin is a type of carotenoid widely used as powerful antioxidant and colourant in aquaculture and the poultry industry. Production of astaxanthin by yeast Xanthophyllomyces dendrorhous has attracted increasing attention due to high cell density and low requirements of water and land compared to photoautotrophic algae. Currently, the regulatory mechanisms of astaxanthin synthesis in X. dendrorhous remain obscure. In this study, we obtained a yellow X. dendrorhous mutant by Atmospheric and Room Temperature Plasma (ARTP) mutagenesis and sequenced its genome. We then identified a putative GATA transcription factor, white collar 2 (XdWC2), from the comparative genome data and verified that disruption of the XdWC2 gene resulted in a similar carotenoid profile to that of the ARTP mutant. Furthermore, transcriptomic analysis and yeast one-hybrid (Y1H) assay showed that XdWC2 regulated the expression of phytoene desaturase gene CrtI and astaxanthin synthase gene CrtS. The yeast two-hybrid (Y2H) assay demonstrated that XdWC2 interacted with white collar 1 (XdWC1) forming a heterodimer WC complex (WCC) to regulate the expression of CrtI and CrtS. Increase of the transcriptional levels of XdWC2 or CrtS in the wild-type strain did not largely modify the carotenoid profile, indicating translational and/or post-translational regulations involved in the biosynthesis of astaxanthin. Overexpression of CrtI in both the wild-type strain and the XdWC2-disrupted strain apparently improved the production of monocyclic carotenoid 3-hydroxy-3', 4'-didehydro-β, ψ-carotene-4-one (HDCO) rather than β-carotene and astaxanthin. The regulation of carotenoid biosynthesis by XdWC2 presented here provides the foundation for further understanding the global regulation of astaxanthin biosynthesis and guides the construction of astaxanthin over-producing strains.

Enhancing astaxanthin yield in Phaffia rhodozyma: current trends and potential of phytohormones

Astaxanthin is an important ketocarotenoid with remarkable biological activities and high economic value. In recent times, natural astaxanthin production by microorganisms has attracted much attention particularly in pharmaceuticals, nutraceuticals, cosmetics, and food and feed industries. Though, currently, productivity is still low and has restricted scale-up application in the commercial market, microbial production of astaxanthin has enormous prospects as it is a greener alternative to the predominating chemical synthesis. Over the years, Phaffia rhodozyma has attracted immense interest particularly in the field of biovalorization and sustainable production of natural nutraceuticals as a promising source of natural astaxanthin since it is able to use agro-food waste as inexpensive nutrient source. Many research works have, thus, been devoted to improving the astaxanthin yield from this yeast. Considering that the yeast was first isolated from tree exudates, the use of phytohormones and plant growth stimulators as prospective stimulants of astaxanthin production in the yeast is promising. Besides, it has been shown in several studies that phytohormones could improve cell growth and astaxanthin production of algae. Nevertheless, this option is less explored for P. rhodozyma. The few studies that have examined the effect of phytohormones on the yeast and its astaxanthin productivity reported positive results, with phytohormones such as 6-benzylaminopurin and gibberellic acid resulting in increased expression of carotenogenesis genes. Although the evidence available is scanty, the results are promising. KEY POINTS: • Phaffia rhodozyma is a promising source of natural astaxanthin • For industrialization, astaxanthin productivity of P. rhodozyma still needs optimization • Phytohormones could potentially augment astaxanthin yield of P. rhodozyma.

Carotenoids: Dietary Sources, Extraction, Encapsulation, Bioavailability, and Health Benefits-A Review of Recent Advancements

Natural carotenoids (CARs), viz. β-carotene, lutein, astaxanthin, bixin, norbixin, capsanthin, lycopene, canthaxanthin, β-Apo-8-carotenal, zeaxanthin, and β-apo-8-carotenal-ester, are being studied as potential candidates in fields such as food, feed, nutraceuticals, and cosmeceuticals. CAR research is advancing in the following three major fields: (1) CAR production from natural sources and optimization of its downstream processing; (2) encapsulation for enhanced physical and chemical properties; and (3) preclinical, clinical, and epidemiological studies of CARs' health benefits. This review critically discusses the recent developments in studies of the chemistry and antioxidant activity, marketing trends, dietary sources, extraction, bioaccessibility and bioavailability, encapsulation methods, dietary intake, and health benefits of CARs. Preclinical, clinical, and epidemiological studies on cancer, obesity, type 2 diabetes (T2D), cardiovascular diseases (CVD), osteoporosis, neurodegenerative disease, mental health, eye, and skin health are also discussed.

Biotechnological advances for improving natural pigment production: a state-of-the-art review

In current years, natural pigments are facing a fast-growing global market due to the increase of people's awareness of health and the discovery of novel pharmacological effects of various natural pigments, e.g., carotenoids, flavonoids, and curcuminoids. However, the traditional production approaches are source-dependent and generally subject to the low contents of target pigment compounds. In order to scale-up industrial production, many efforts have been devoted to increasing pigment production from natural producers, via development of both in vitro plant cell/tissue culture systems, as well as optimization of microbial cultivation approaches. Moreover, synthetic biology has opened the door for heterologous biosynthesis of pigments via design and re-construction of novel biological modules as well as biological systems in bio-platforms. In this review, the innovative methods and strategies for optimization and engineering of both native and heterologous producers of natural pigments are comprehensively summarized. Current progress in the production of several representative high-value natural pigments is also presented; and the remaining challenges and future perspectives are discussed.