Two-dimensional liquid chromatography analysis of all-trans-, 9-cis-, and 13-cis-astaxanthin in raw extracts from Phaffia rhodozyma

New strategies to study in depth the metabolic mechanism of astaxanthin biosynthesis in Phaffia rhodozyma

Astaxanthin, a ketone carotenoid known for its high antioxidant activity, holds significant potential for application in nutraceuticals, aquaculture, and cosmetics. The increasing market demand necessitates a higher production of astaxanthin using Phaffia rhodozyma. Despite extensive research efforts focused on optimizing fermentation conditions, employing mutagenesis treatments, and utilizing genetic engineering technologies to enhance astaxanthin yield in P. rhodozyma, progress in this area remains limited. This review provides a comprehensive summary of the current understanding of rough metabolic pathways, regulatory mechanisms, and preliminary strategies for enhancing astaxanthin yield. However, further investigation is required to fully comprehend the intricate and essential metabolic regulation mechanism underlying astaxanthin synthesis. Specifically, the specific functions of key genes, such as crtYB, crtS, and crtI, need to be explored in detail. Additionally, a thorough understanding of the action mechanism of bifunctional enzymes and alternative splicing products is imperative. Lastly, the regulation of metabolic flux must be thoroughly investigated to reveal the complete pathway of astaxanthin synthesis. To obtain an in-depth mechanism and improve the yield of astaxanthin, this review proposes some frontier methods, including: omics, genome editing, protein structure-activity analysis, and synthetic biology. Moreover, it further elucidates the feasibility of new strategies using these advanced methods in various effectively combined ways to resolve these problems mentioned above. This review provides theory and method for studying the metabolic pathway of astaxanthin in P. rhodozyma and the industrial improvement of astaxanthin, and provides new insights into the flexible combined use of multiple modern advanced biotechnologies.

The Biosynthesis of Astaxanthin Esters in Schizochytrium sp. is Mediated by a Bifunctional Diacylglycerol Acyltransferase

Astaxanthin esters are a major form of astaxanthin found in nature. However, the exact mechanisms of the biosynthesis and storage of astaxanthin esters were previously unknown. We found that Schizochytrium sp. synthesized both astaxanthin and docosahexaenoic acid (DHA)-enriched lipids. The major type of astaxanthin produced was free astaxanthin along with astaxanthin-DHA monoester and other esterified forms. DHA accounted for 41.0% of the total fatty acids from astaxanthin monoesters. These compounds were deposited mainly in lipid droplets. The biosynthesis of the astaxanthin esters was mainly carried out by a novel diacylglycerol acyltransferase ScDGAT2-1, while ScDGAT2-2 was involved only in the production of triacylglycerol. We also identified astaxanthin ester synthases from the astaxanthin-producing algae Haematococcus pluvialis and Chromochloris zofingiensis, as well as a thraustochytrid Hondaea fermentalgiana with an unknown carotenoid profile. This investigation enlightens the application of thraustochytrids for the production of both DHA and astaxanthin and provides enzyme resources for the biosynthesis of astaxanthin esters in the engineered microbes.

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.

Isomerization of carotenoids in photosynthesis and metabolic adaptation

In nature, carotenoids are present as trans- and cis-isomers. Various physical and chemical factors like light, heat, acids, catalytic agents, and photosensitizers can contribute to the isomerization of carotenoids. Living organisms in the process of evolution have developed different mechanisms of adaptation to light stress, which can also involve isomeric forms of carotenoids. Particularly, light stress conditions can enhance isomerization processes. The purpose of this work is to review the recent studies on cis/trans isomerization of carotenoids as well as the role of carotenoid isomers for the light capture, energy transfer, photoprotection in light-harvesting complexes, and reaction centers of the photosynthetic apparatus of plants and other photosynthetic organisms. The review also presents recent studies of carotenoid isomers for the biomedical aspects, showing cis- and trans-isomers differ in bioavailability, antioxidant activity and biological activity, which can be used for therapeutic and prophylactic purposes.

Enhancement of astaxanthin production in Haematococcus pluvialis using zinc oxide nanoparticles

Today, there is a great interest in using astaxanthin due to its potential health advantages. Application of different types of nanoparticles (NPs) as stress agents to enhance astaxanthin production in Haematococcus pluvialis, a microalgae strain, has been reported in the literature. In this study, the effect of different concentrations of zinc oxide (ZnO) NPs on the enhancement of astaxanthin production in H. pluvialis was investigated. First, ZnO NPs were synthesized from zinc nitrate as the precursor and sodium hydroxide (chemical method), and peel extract of pomegranate (green method) as reducing agents. To study the cell viability and stimulate the astaxanthin production, H. pluvialis cells were exposed to the different concentrations (i.e. 50, 100, 200, and 400 μg.ml^-1) of ZnO NPs. The synthesized powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS) methods. The characterization results showed that the pure ZnO NPs were successfully synthesized via both methods with uniform particle size distribution. But, the average particle size of the green synthesized ZnO NPs (about 30 nm) was smaller than that of the chemically synthesized ones (about 80 nm). Maximum astaxanthin production (~ 20 mg.g^-1 of dry biomass of H. pluvialis) was achieved at 100 μg.ml^-1 of green synthesized ZnO NPs exposure to the H. pluvialis in comparison with the control culture after 15 days. However, ZnO NPs concentration above 200 μg.ml^-1 was toxic to the microalgae. From these results, it can be concluded that a specific amount of ZnO NPs could be considered as a worthy candidate for the enhancement of astaxanthin production in H. pluvialis.

Dietary astaxanthin: an excellent carotenoid with multiple health benefits

Astaxanthin is a carotenoid widely found in marine organisms and microorganisms. With extensive use in nutraceuticals, cosmetics, and animal feed, astaxanthin will have the largest share in the global market for carotenoids in the near future. Owing to its unique molecular features, astaxanthin has excellent antioxidant activity and holds promise for use in biochemical studies. This review focuses on the observed health benefits of dietary astaxanthin, as well as its underlying bioactivity mechanisms. Recent studies have increased our understanding of the role of isomerization and esterification in the structure-function relationship of dietary astaxanthin. Gut microbiota may involve the fate of astaxanthin during digestion and absorption; thus, further knowledge is needed to establish accurate recommendations for dietary intake of both healthy and special populations. Associated with the regulation of redox balance and multiple biological mechanisms, astaxanthin is proposed to affect oxidative stress, inflammation, cell death, and lipid metabolism in humans, thus exerting benefits for skin condition, eye health, cardiovascular system, neurological function, exercise performance, and immune response. Additionally, preclinical trials predict its potential effects such as intestinal flora regulation and anti-diabetic activity. Therefore, astaxanthin is worthy of further investigation for boosting human health, and wide applications in the food industry.

Residue measurement of pendimethalin in tobacco by using heart-cutting two dimensional liquid chromatography coupled with tandem mass spectrometry

A novel heart-cutting two-dimensional liquid chromatography coupled with tandem mass spectrometry method was developed for quantitative analysis of pendimethalin residue in tobacco. The strategy of reversed phase liquid chromatography coupled with another reversed-phase liquid chromatography was employed for high column efficiency and excellent compatibility of mobile phase. In the first dimensional chromatography, a cyano column with methanol/water as the eluent was applied to separate pendimethalin from thousands of interference components in tobacco. By heart-cutting technique, which effectively removed interference components, the target compound was cut to the second dimensional C18 column for further separation. The pendimethalin residue was finally determined by the tandem mass spectrometry under multiple reaction monitoring reversed-phase liquid chromatography mode. Sample pretreatment of the new method was simplified, involving only extraction and filtration. Compared with traditional methodologies, the new method showed fairly high selectivity and sensitivity with almost no matrix interference. The limit of quantitation for pendimethalin was 1.21 ng/mL, whereas the overall recoveries ranged from 95.7 to 103.3%. The new method has been successfully applied to non-stop measure of 200 real samples, without contamination of ion source. Detection results of the samples agreed well with standard method.