Exercise-induced fatigue represents a complex physiological response triggered by physical exertion,with its mechanisms primarily originating from central and peripheral systems.Central fatigue arises from neurotransm...Exercise-induced fatigue represents a complex physiological response triggered by physical exertion,with its mechanisms primarily originating from central and peripheral systems.Central fatigue arises from neurotransmitter imbalances such as elevated serotonin and reduced dopamine levels,leading to drowsiness and diminished motor performance.Peripheral fatigue occurs at the muscular level,where energy depletion,metabolic waste accumulation,and oxidative stress impair muscle contraction function.Astaxanthin,a potent antioxidant,directly and primarily alleviates peripheral fatigue through its antioxidant,anti-inflammatory,and mitochondrial protective effects.Simultaneously,by improving the peripheral environment and reducing the transmission of fatigue signals to the brain,it indirectly helps alleviate central fatigue.Based on this,this paper reviews the mechanisms of action and related research progress of astaxanthin on exercise-induced fatigue,and discusses its application value and challenges based on the current status.展开更多
Oxidative stress is considered as a critical factor in the process of pathological diseases,and mitochondria are considered as vital target organelles for disease intervention.The purpose of this study was aimed to ev...Oxidative stress is considered as a critical factor in the process of pathological diseases,and mitochondria are considered as vital target organelles for disease intervention.The purpose of this study was aimed to evaluate the antioxidant efficacy of mitochondria-targeted astaxanthin nanoparticle on hydrogen peroxideinduced oxidative damage.As expected,mitochondria-targeted nanoparticle showed excellent mitochondria co-localization ability with higher Pearson's correlation coefficient(r=0.88).In vitro experiments suggested that the mitochondria-targeted astaxanthin nanoparticle could promote cell viability and increase antioxidantrelated enzyme activities.Simultaneously,metabolomics analysis indicated that mitochondria-targeted astaxanthin nanoparticle could alleviate oxidative stress by regulating amino acid metabolism and energy metabolism.Altogether,all these results strongly confirmed the mitochondria-targeted strategy for astaxanthin delivery could relieve oxidative stress and had great promise in the application of disease intervention.展开更多
Saline treatment is a low-cost,simple,and effective method to stimulate astaxanthin accumulation in Haematococcus pluvialis,and is proposed to be applied in the second stage of a 2-stage culture since it does not nece...Saline treatment is a low-cost,simple,and effective method to stimulate astaxanthin accumulation in Haematococcus pluvialis,and is proposed to be applied in the second stage of a 2-stage culture since it does not necessitate changing the medium.To understand the effect of salinity on the astaxanthin production of H.pluvialis,the photosynthetic activity and the biocomponents production in 1-and 2-stage cultures in different salinities were investigated.Except for astaxanthin synthesis,which increased at low salinities of 2 and 5-g/L NaCl,most biocomponent yields decreased in 1-stage cultures as salinity increased.At a salinity of 5-g/L NaCl,the 2-stage culture further increased astaxanthin production to 18.41±0.24 mg/L,which was more than 2.0 times that of the control.Saline treatment led to an overall decrease in photosynthetic performance indices of H.pluvialis,and had an impact on five sites of the electron transport chain:the energy connection between antenna and reaction center of photosystemⅡ(PSⅡ),oxygen evolving complex activity on the donor side,the electron transfer from plastoquinone A(Q_(A))to plastoquinone B(Q_(B))and from plastoquinone(PQ)to receptor side of photosystem I(PS I),and the pool size of the end electron acceptors in PSⅠacceptor side.The excitation imbalance between PSⅠand PSⅡcaused by the variance in the electron transfer chain necessitated the synthesis of antioxidants like astaxanthin in order to ensure cell viability.The accumulation of astaxanthin was found to be closely correlated with the stabilized or enhanced the maximum relative electron transfer rate(rETR_(max))and the PSⅡactual quantum yield(QY_(SS))as well as the increased fluorescence yield at J-step(V_(J)).This work offers the novel insight of how saline stress controls H.pluvialis photosynthetic activity and astaxanthin synthesis.展开更多
Autophagy directly regulates the amyloid beta-peptide(Aβ)clearance,and its dysfunction occurs in the early pathogenesis of Alzheimer's disease(AD).We previously reported that docosahexaenoic acid-acylated astaxan...Autophagy directly regulates the amyloid beta-peptide(Aβ)clearance,and its dysfunction occurs in the early pathogenesis of Alzheimer's disease(AD).We previously reported that docosahexaenoic acid-acylated astaxanthin monoester(AST-DHA)showed neuroprotection against AD pathology.However,its in-depth mechanism and autophagic responses in AD brains are poorly understood.Herein,SH-SY5Y cells overexpressing the Swedish mutation(K595N/M596L)of APP gene were established to preliminarily evaluate the actions of AST-DHA on reducing Aβ_(1-42)levels and regulating autophagy.In microglial BV2 cells,AST-DHA and free astaxanthin(F-AST)recovered p62 and LC3Ⅱ/Ⅰlevels,and restored autophagy flux by rescuing the late phase of microglial autophagy.Notably,autophagic inhibitor bafilomycin A1 blunted the abilities of AST-DHA to reduce Aβ_(1-42)and fibral Aβ,suggesting that AST-DHA probably promoted Aβclearance in a microglial autophagy-dependent manner.Further studies in APP/PS1 mice verified that dietary AST-DHA and F-AST promoted Aβphagocytosis via microglial autophagy.Significant decreases of Iba1 and p62 were observed around Aβplaque in the hippocampus and cortex using triple fluorescence staining.Furthermore,AST-DHA exhibited superior performance over F-AST in restoring autophagic dysfunction,ameliorating Aβburden and cognitive deficit.Our findings suggest a possible mechanism of AST-DHA in improving AD by which it restores microglial autophagy to facilitate cerebral Aβclearance.It supports the future application of AST-DHA as an autophagic regulator in maintaining brain function.展开更多
Astaxanthin(AX)and vitamin E(VE)are widely consumed nutritional supplements in China,with its beneficial effects predominantly attributed to all-trans AX and VE.The aim of this study is to develop and validate a rapid...Astaxanthin(AX)and vitamin E(VE)are widely consumed nutritional supplements in China,with its beneficial effects predominantly attributed to all-trans AX and VE.The aim of this study is to develop and validate a rapid and accurate method for quantifying the content of AX and VE in nutritional supplement products using highly sensitive1H NMR method.Coumarin was chosen as the internal standard.Specific signals from AX was optimal at H-7,7'in the chemical shift range ofδ6.17–6.24 ppm,whereas the signals of VE atδ2.59 ppm.To demonstrate the reliability of this analytical approach the proposed method underwent rigorous validation,specificity,limit of detection(LOD),limit of quantitation(LOQ),linearity,accuracy,precision,and recovery.The accuracy of the validation method was 3.10%for AX and 1.99%for VE.The results indicated that the method was precise and reliable.The method has been successfully applied to simultaneous quantification of AX and VE in nutritional supplements products.展开更多
Background:Dry eye disease(DED)predominantly results from elevated tear film os-molarity,which can not only cause ocular inconvenience but may lead to visual impair-ments,severely compromising patient well-being and e...Background:Dry eye disease(DED)predominantly results from elevated tear film os-molarity,which can not only cause ocular inconvenience but may lead to visual impair-ments,severely compromising patient well-being and exerting substantial economic burdens as well.Astaxanthin(AST),a member of the xanthophylls and recognized for its robust abilities to combat inflammation and oxidation,is a common dietary sup-plement.Nonetheless,the precise molecular pathways through which AST influences DED are still poorly understood.Methods:Therapeutic targets for AST were identified using data from the GeneCards,PharmMapper,and Swiss Target Prediction databases,and STITCH datasets.Similarly,targets for dry eye disease(DED)were delineated leveraging resources such as the Therapeutic Target Database(TTD),DisGeNET,GeneCards,and OMIM databases,and DrugBank datasets.Interactions among shared targets were charted and dis-played using CytoScape 3.9.0.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted to elucidate the functions of pivotal tar-gets within the protein-protein interaction network.Molecular interactions between AST and key targets were confirmed through molecular docking using AutoDock and PyMOL.Molecular dynamics simulations were performed using GROMACS 2022.3.Viability of human corneal epithelial cells(hCEC)was assessed across varying concen-trations of AST.A mouse model of experimental DED was developed using 0.1%ben-zalkonium chloride(BAC),and the animals were administered 100 mg/kg/day of AST orally for 7 days.The efficacy of the treatments was assessed through a series of di-agnostic tests to evaluate the condition of the ocular surface after the interventions.The levels of inflammation and oxidative stress were quantitatively assessed using methods such as reverse transcription-polymerase chain reaction(RT-PCR),Western blot,and immunofluorescence staining.Results:Network pharmacology suggests that AST may alleviate DED by influenc-ing oxidation-reduction signaling pathways and reducing oxidative stress provoked by BAC.In vivo experiments demonstrated an improved overall condition in AST-administered mice in contrast to the control group.Immunofluorescence staining analyses indicated a decrease in Keap1 protein in the corneal tissues of AST-treated mice and a significant increase in Nrf2 and HO-1 protein.In vitro studies demon-strated that AST significantly enhanced cell viability and suppressed reactive oxy-gen species expression under hyperosmotic(HS)conditions,thereby protecting the human corneal epithelium.Conclusion:AST is capable of shielding mice from BAC-induced DED,decelerating the progression of DED,and mitigating oxidative stress damage under HS conditions in hCEC cells.The protective impact of AST on DED may operate through stimulating the Keap1-Nrf2/HO-1 signaling pathway.Our research findings indicate that AST may be a promising treatment for DED,offering new insights into DED treatment.展开更多
The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great po...The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability.However,excessive degradation rate and the delayed surface endothelialization still limit their further application.In this study,we modified a Mg-Zn-Y-Nd alloy(ZE21B)by preparing MgF_(2) as the corrosion resistance layer,the dopamine polymer film(PDA)as the bonding layer,and hyaluronic acid(HA)loaded astaxanthin(ASTA)as an important layer to directing the cardiovascular cells fate.The electrochemical test results showed that the MgF_(2)/PDA/HA-ASTA coating improved the corrosion resistance of ZE21B.The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation,inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages.Compared with the HAloaded rapamycin(RAPA)coating,our MgF_(2)/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility,indicating stronger multi-functions for the ZE21B alloy on cardiovascular application.展开更多
Aim： To evaluate the treatment of male infertility with a strong natural antioxidant, in addition to conventional treatment. Methods： Using a double blind, randomized trial design, 30 men with infertility of ≥12 mo...Aim： To evaluate the treatment of male infertility with a strong natural antioxidant, in addition to conventional treatment. Methods： Using a double blind, randomized trial design, 30 men with infertility of ≥12 months and female partners with no demonstrable cause of infertility received conventional treatment according to the guidelines of the World Health Organization （WHO）, and either a strong antioxidant Astaxanthin 16 rag/day （AstaCarox, AstaReal AB, Gustavsberg, Sweden） or placebo for 3 months. The effects of treatment on semen parameters, reactive oxygen species （ROS）, zona-free hamster oocyte test, serum hormones including testosterone, luteinizing hormone （LH）, follicle stimulating hormone （FSH） and Inhibin B, and spontaneous or intrauterine insemination （IUI）-induced pregnancies were evaluated. Results： ROS and Inhibin B decreased significantly and sperm linear velocity increased in the Astaxanthin group （n = 11）, but not in the placebo group （n = 19）. The results of the zona-free hamster oocyte test tended to improve in the Astaxanthin group in contrast with the placebo group, though not reaching statistical significance. The total and per cycle pregnancy rates among the placebo cases （10.5 % and 3.6 %） were lower compared with 54.5 % and 23. 1% respectively in the Astaxanthin group （P=0.028; P=0.036）. Conclusion： Although the present study suggests a positive effect of Astaxanthin on sperm parameters and fertility, the results need to be confirmed in a larger trial before recommending Astaxanthin for the complementary treatment of infertile men. （Asian J Androl 2005 Sep; 7： 257-262）展开更多
Optimization of a process for extracting astaxanthin from Phaffia rhodozyma by acidic method was investigated, regarding several extraction factors such as acids, organic solvents, temperature and time. Fractional fac...Optimization of a process for extracting astaxanthin from Phaffia rhodozyma by acidic method was investigated, regarding several extraction factors such as acids, organic solvents, temperature and time. Fractional factorial design, central composite design and response surface methodology were used to derive a statistically optimal model, which corresponded to the following optimal condition： concentration of lactic acid at 5.55 mol/L, ratio of ethanol to yeast dry weight at 20.25 ml/g, temperature for cell-disruption at 30 ℃, and extraction time for 3 min. Under this condition, astaxanthin and the total carotenoids could be extracted in amounts of 1294.7 μg/g and 1516.0 μg/g, respectively. This acidic method has advantages such as high extraction efficiency, low chemical toxicity and no special requirement of instruments. Therefore, it might be a more feasible and practical method for industrial practice.展开更多
A method for determination of astaxanthin and astaxanthin eaters in shrimp shell by high performance liquid chromatography is established.Shrimp shell are addressed with 5%hydrochloric acid to remove calcium ions.Afte...A method for determination of astaxanthin and astaxanthin eaters in shrimp shell by high performance liquid chromatography is established.Shrimp shell are addressed with 5%hydrochloric acid to remove calcium ions.After shell is dried,organics from shrimp shell are extracted with anhydrous ethanol.The alcohol extrative of the shrimp shell is mixed with the ammonium sulfate to extract astaxanthin by aqueous two-phase extraction.The crude astaxanthin is collected,which is distributed in the middle layer of the aqueous two-phase layer.After distilled water is added to the crude astaxanthin,the aqueous solution is centrifuged,and the previous step is repeated for several times.The precipitation in centrifuge tube is collected and dried.The crude astaxanthin dried is dissolved with acetone,and the sample solution is separated by TLC.Every pigment on the TLC plate is collected and dissolved with acetone.The pigments are determined by high performance liquid chromatograph.The results show that aqueous two-phase system,3 mL alcohol extractive of astaxanthin and 4.5 mL 20%ammonium sulfate,can be used to acquire crude astaxanthin.The wavelength of the maximum peak of astaxanthin in ethanol solution is 472 nm.A variety of pigments can be separated from the crude astaxanthin by thin-layer chromatography,including free astaxanthin,astaxanthin monoester,astaxanthin diester,echinenone and other substances.It can be seen from high performance liquid chromatography that the appearance time of free astaxanthin is from 4 min to 5.5 min,and the appearance time of astaxanthin monoester is from 10.5 min to 27.8 min.The method is simple about the sample pretreatment and feasible about the determination of astaxanthin and astaxanthin esters in shrimp shell.展开更多
Fermentation of Phaffia rhodozyma is a major method for producing astaxanthin, an important pigment with industrial and pharmaceutical application. To improve astaxanthin productivity, single factor and mixture design...Fermentation of Phaffia rhodozyma is a major method for producing astaxanthin, an important pigment with industrial and pharmaceutical application. To improve astaxanthin productivity, single factor and mixture design experiments were used to investigate the effects of nitrogen source on Phaffia rhodozyma cultivation and astaxanthin production. Results of single factor experiments showed nitrogen source could significantly affect P. rhodozyma cultivation with respect to carbon source utilization, yeast growth and astaxanthin accumulation. Further studies of mixture design experiments using (NH4)2SO4, KNO3 and beef extract as nitrogen sources indicated that the proportion of three nitrogen sources was very important to astaxanthin production. Validation experiments showed that the optimal nitrogen source was composed of 0.28 g/L (NH4)2SO4, 0.49 g/L KNO3 and 1.19 g/L beef extract. The kinetic characteristics of batch cultivation were investigated in a 5-L pH-stat fermentor. The maximum amount of biomass and highest astaxanthin yield in terms of volume and in terms of biomass were 7.71 mg/L and 1.00 mg/g, respectively.展开更多
An algal astaxanthin feeding trial was carried out to investigate the ef fects of natural astaxanthin from Haematococcus pluvialis as feed additives on growth, pigmenting efficacy and antioxidant capacity in blood par...An algal astaxanthin feeding trial was carried out to investigate the ef fects of natural astaxanthin from Haematococcus pluvialis as feed additives on growth, pigmenting efficacy and antioxidant capacity in blood parrot(C ichlasoma citrinellum × C ichlasoma. synspilum). Tissue total antioxidant capacity(TAC), superoxide dismutase(SOD), catalase(CAT) and maleic dialdehyde(MDA) were chosen as measures of its antioxidant capacity. All fish which received an astaxanthin(from micro-algal H. pluvialis) supplemented diet with 400 mg/kg of astaxanthin, after 50 days of feeding, the astaxanthin-fed fish displayed a pinkcolored skin and the control-fed fish displayed a grayish skin. For the growth, the weight gains of controlfed fish and astaxanthin-fed fish were 200% and 300%, respectively. Samples of skin and scales were used for analysis of total carotenoids and astaxanthin content, and fish feeding astaxanthin showed significantly( P <0.05) higher concentrations than the control group, indicating that the pigmentation of this fish had been significantly improved by dietary astaxanthin. Compared with the control fish, pigmented fish had lower SOD, CAT and MDA and higher TAC. It can be concluded that supplementation with dietary astaxanthin could eff ectively enhance growth, skin coloration and the antioxidant capacity of this fish. This study will provide a reference for application of natural astaxanthin from H. pluvialis as feed additives in blood parrot artificial breeding. Our data is also useful in ornamental fish farming, especially when the retentivity of astaxanthin in the skin and scales are involved. It is leading to the possibility of increasing the pigmentation of farmed-fish by adding the powdered form of H. pluvialis to the diet as an ef fective pigment.展开更多
In this paper,we investigated the effects of temperature,oxygen,antioxidants,and corn germ oil on the stability of astaxanthin from Haematococcus pluvialis under different storage conditions,and changes in the composi...In this paper,we investigated the effects of temperature,oxygen,antioxidants,and corn germ oil on the stability of astaxanthin from Haematococcus pluvialis under different storage conditions,and changes in the composition of astaxanthin esters during storage using high performance liquid chromatography and spectrophotometry.Oxygen and high temperatures(22–25°C) significantly reduced the stability of astaxanthin esters.Corn germ oil and antioxidants(ascorbic acid and vitamin E)failed to protect astaxanthin from oxidation,and actually significantly increased the instability of astaxanthin.A change in the relative composition of astaxanthin esters was observed after 96 weeks of long-term storage.During storage,the relative amounts of free astaxanthin and astaxanthin monoesters declined,while the relative amount of astaxanthin diesters increased.Thus,the ratio of astaxanthin diester to monoester increased,and this ratio could be used to indicate if astaxanthin esters have been properly preserved.If the ratio is greater than 0.2,it suggests that the decrease in astaxanthin content could be higher than 20%.Our results show that storing algal powder from H.pluvialis or other natural astaxanthin products under vacuum and in the dark below 4°C is the most economical and applicable storage method for the large-scale production of astaxanthin from H.pluvialis.This storage method can produce an astaxanthin preservation rate of at least 80%after 96 weeks of storage.展开更多
method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the ...method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the concentration of HCl was 0.4 mol.L^-1, the highest extraction efficiency of astaxanthin was achieved which was about three times higher than the control. Acetone or benzene as single polar or non-polar solvent was the most ef- fective solvent in our research. With a combination of isopropanol and n-hexane （volume ratio of 2 ： 1）, the maxi- mal extraction efficiency was achieved, approximately 60% higher than that obtained with a single solvent. The liquid-solid ratio and the extracting time were also optimized. Under the optimum extraction conditions, the extraction yield of astaxanthin exceeded 98%.展开更多
The optimum concentration of Na_2 WO_4 was explored in relation to the cell density and astaxanthin content in Haematococcus pluvialis. Then, the cellular morphology, nitrate reductase(NR) activity, soluble sugar and ...The optimum concentration of Na_2 WO_4 was explored in relation to the cell density and astaxanthin content in Haematococcus pluvialis. Then, the cellular morphology, nitrate reductase(NR) activity, soluble sugar and protein contents, and chlorophyll ?uorescence were measured, and the transcriptional expression of carotenogenic genes was determined by quantitative real-time PCR. The results showed that 3.0 mmol/L of Na_2 WO_4 was the optimum concentration to induce astaxanthin accumulation, with a maximum content of 49.41±0.13 pg/cell reached on the tenth day. The NR activity decreased signi?cantly and continually after Na_2 WO_4 treatment. The soluble sugar content increased gradually during the experimental period and was eventually signi?cantly higher than that in the control. The soluble protein content increased rapidly,reached a maximum in day 0.5 and day 1 and then decreased. The ef fective photochemical effciency of PSII( F v'/F m') and light saturation( E k) ?rst decreased and then tended to stabilize, and NADP +-glyceraldehyde-3-phosphate dehydrogenase(GAPDH) gene expression was correlated with photosynthesis. The transcriptional expression of ipi, psy and bkt was signi?cantly increased compared with that in the control after application of Na_2 WO_4, and the relative expression of ipi reached the highest level on the ?fth day, with a 98.03±1.92-fold increase. Our results describe a new approach to promote the ef fective accumulation of astaxanthin in H. pluvialis by NR inhibitor Na_2 WO_4.展开更多
A derivative ratio spectrophotometric method was used for the simultaneous determination of β-carotene and astaxanthin produced from Phaffia rhodozyma. Absorbencies of a series of the standard carotenoids in the rang...A derivative ratio spectrophotometric method was used for the simultaneous determination of β-carotene and astaxanthin produced from Phaffia rhodozyma. Absorbencies of a series of the standard carotenoids in the range of 441 nm to 490 nm demonstrated that their absorptive spectra accorded with Beer’s law and that the additivity when the concentrations of β-carotene and astaxanthin and their mixture were within the range of 0 to 5 μg/ml, 0 to 6 μg/ml, and 0 to 6 μg/ml, respectively. When the wavelength interval (?λ) at 2 nm was selected to calculate the first derivative ratio spectra values, the first derivative amplitudes at 461 nm and 466 nm were suitable for quantitatively determining β-carotene and astaxanthin, respectively. Effect of divisor on derivative ratio spectra could be neglected; any concentration used as divisor in range of 1.0 to 4.0 μg/ml is ideal for calculating the derivative ratio spectra values of the two carotenoids. Calibration graphs were established for β-carotene within 0?6.0 μg/ml and for astaxanthin within 0?5.0 μg/ml with their corresponding regressive equations in: y=?0.0082x?0.0002 and y=0.0146x?0.0006, respectively. R-square values in excess of 0.999 indicated the good linearity of the calibration graphs. Sample recovery rates were found satisfactory (>99%) with relative standard deviations (RSD) of less than 5%. This method was suc- cessfully applied to simultaneous determination of β-carotene and astaxanthin in the laboratory-prepared mixtures and the extract from the Phaffia rhodozyma culture.展开更多
This study engineered β-carotene ketolase CrtW and β-carotene hydroxylase CrtZ to improve biosynthesis of astaxanthin in Escherichia coli. Firstly, crtW was randomly mutated to increase CrtW activities on conversion...This study engineered β-carotene ketolase CrtW and β-carotene hydroxylase CrtZ to improve biosynthesis of astaxanthin in Escherichia coli. Firstly, crtW was randomly mutated to increase CrtW activities on conversion from β-carotene to astaxanthin. A crtW* mutant with A6 T, T105 A and L239 M mutations has improved 5.35-fold astaxanthin production compared with the wild-type control. Secondly, the expression levels of crtW* and crtZ on chromosomal were balanced by simultaneous modulation RBS regions of their genes using RBS library. The strain RBS54 selected from RBS library, directed the pathway exclusively towards the desired product astaxanthin as predominant carotenoid(99%). Lastly, the number of chromosomal copies of the balanced crtW*-crtZ cassette from RBS54 was increased using a Cre-loxP based technique, and a strain with 30 copies of the crtW*-crtZ cassette was selected. This final strain DL-A008 had a 9.8-fold increase of astaxanthin production compared with the wild-type control. Fed-batch fermentation showed that DL-A008 produced astaxanthin as predominant carotenoid(99%) with a specific titer of 0.88 g·L^(-1) without addition of inducer. In conclusion, through constructing crtW mutation, balancing the expression levels between crtW* and crtZ, and increasing the copy number of the balanced crtW*-crtZ cassette, the activities of β-carotene ketolase and β-carotene hydroxylase were improved for conversion of β-carotene to astaxanthin with higher efficiency. The series of conventional and novel metabolic engineering strategies were designed and applied to construct the astaxanthin hetero-producer strain of E. coli, possibly offering a general approach for the construction of stable hetero-producer strains for other natural products.展开更多
文摘Exercise-induced fatigue represents a complex physiological response triggered by physical exertion,with its mechanisms primarily originating from central and peripheral systems.Central fatigue arises from neurotransmitter imbalances such as elevated serotonin and reduced dopamine levels,leading to drowsiness and diminished motor performance.Peripheral fatigue occurs at the muscular level,where energy depletion,metabolic waste accumulation,and oxidative stress impair muscle contraction function.Astaxanthin,a potent antioxidant,directly and primarily alleviates peripheral fatigue through its antioxidant,anti-inflammatory,and mitochondrial protective effects.Simultaneously,by improving the peripheral environment and reducing the transmission of fatigue signals to the brain,it indirectly helps alleviate central fatigue.Based on this,this paper reviews the mechanisms of action and related research progress of astaxanthin on exercise-induced fatigue,and discusses its application value and challenges based on the current status.
基金supported by the National Science Fund for Distinguished Young Scholars of China(31925031)Mount Tai Industrial Blue Talent Program of Shandong Province(tsls20231209)。
文摘Oxidative stress is considered as a critical factor in the process of pathological diseases,and mitochondria are considered as vital target organelles for disease intervention.The purpose of this study was aimed to evaluate the antioxidant efficacy of mitochondria-targeted astaxanthin nanoparticle on hydrogen peroxideinduced oxidative damage.As expected,mitochondria-targeted nanoparticle showed excellent mitochondria co-localization ability with higher Pearson's correlation coefficient(r=0.88).In vitro experiments suggested that the mitochondria-targeted astaxanthin nanoparticle could promote cell viability and increase antioxidantrelated enzyme activities.Simultaneously,metabolomics analysis indicated that mitochondria-targeted astaxanthin nanoparticle could alleviate oxidative stress by regulating amino acid metabolism and energy metabolism.Altogether,all these results strongly confirmed the mitochondria-targeted strategy for astaxanthin delivery could relieve oxidative stress and had great promise in the application of disease intervention.
基金Supported by the National Natural Science Foundation of China(Nos.42177459,41776156,41271521)。
文摘Saline treatment is a low-cost,simple,and effective method to stimulate astaxanthin accumulation in Haematococcus pluvialis,and is proposed to be applied in the second stage of a 2-stage culture since it does not necessitate changing the medium.To understand the effect of salinity on the astaxanthin production of H.pluvialis,the photosynthetic activity and the biocomponents production in 1-and 2-stage cultures in different salinities were investigated.Except for astaxanthin synthesis,which increased at low salinities of 2 and 5-g/L NaCl,most biocomponent yields decreased in 1-stage cultures as salinity increased.At a salinity of 5-g/L NaCl,the 2-stage culture further increased astaxanthin production to 18.41±0.24 mg/L,which was more than 2.0 times that of the control.Saline treatment led to an overall decrease in photosynthetic performance indices of H.pluvialis,and had an impact on five sites of the electron transport chain:the energy connection between antenna and reaction center of photosystemⅡ(PSⅡ),oxygen evolving complex activity on the donor side,the electron transfer from plastoquinone A(Q_(A))to plastoquinone B(Q_(B))and from plastoquinone(PQ)to receptor side of photosystem I(PS I),and the pool size of the end electron acceptors in PSⅠacceptor side.The excitation imbalance between PSⅠand PSⅡcaused by the variance in the electron transfer chain necessitated the synthesis of antioxidants like astaxanthin in order to ensure cell viability.The accumulation of astaxanthin was found to be closely correlated with the stabilized or enhanced the maximum relative electron transfer rate(rETR_(max))and the PSⅡactual quantum yield(QY_(SS))as well as the increased fluorescence yield at J-step(V_(J)).This work offers the novel insight of how saline stress controls H.pluvialis photosynthetic activity and astaxanthin synthesis.
基金supported by the National Natural Science Foundation of China(32302063)Shandong Provincial Natural Science Foundation(ZR2023QC130)。
文摘Autophagy directly regulates the amyloid beta-peptide(Aβ)clearance,and its dysfunction occurs in the early pathogenesis of Alzheimer's disease(AD).We previously reported that docosahexaenoic acid-acylated astaxanthin monoester(AST-DHA)showed neuroprotection against AD pathology.However,its in-depth mechanism and autophagic responses in AD brains are poorly understood.Herein,SH-SY5Y cells overexpressing the Swedish mutation(K595N/M596L)of APP gene were established to preliminarily evaluate the actions of AST-DHA on reducing Aβ_(1-42)levels and regulating autophagy.In microglial BV2 cells,AST-DHA and free astaxanthin(F-AST)recovered p62 and LC3Ⅱ/Ⅰlevels,and restored autophagy flux by rescuing the late phase of microglial autophagy.Notably,autophagic inhibitor bafilomycin A1 blunted the abilities of AST-DHA to reduce Aβ_(1-42)and fibral Aβ,suggesting that AST-DHA probably promoted Aβclearance in a microglial autophagy-dependent manner.Further studies in APP/PS1 mice verified that dietary AST-DHA and F-AST promoted Aβphagocytosis via microglial autophagy.Significant decreases of Iba1 and p62 were observed around Aβplaque in the hippocampus and cortex using triple fluorescence staining.Furthermore,AST-DHA exhibited superior performance over F-AST in restoring autophagic dysfunction,ameliorating Aβburden and cognitive deficit.Our findings suggest a possible mechanism of AST-DHA in improving AD by which it restores microglial autophagy to facilitate cerebral Aβclearance.It supports the future application of AST-DHA as an autophagic regulator in maintaining brain function.
基金the Fundamental Research Funds for the Central Universities(No.202351011)。
文摘Astaxanthin(AX)and vitamin E(VE)are widely consumed nutritional supplements in China,with its beneficial effects predominantly attributed to all-trans AX and VE.The aim of this study is to develop and validate a rapid and accurate method for quantifying the content of AX and VE in nutritional supplement products using highly sensitive1H NMR method.Coumarin was chosen as the internal standard.Specific signals from AX was optimal at H-7,7'in the chemical shift range ofδ6.17–6.24 ppm,whereas the signals of VE atδ2.59 ppm.To demonstrate the reliability of this analytical approach the proposed method underwent rigorous validation,specificity,limit of detection(LOD),limit of quantitation(LOQ),linearity,accuracy,precision,and recovery.The accuracy of the validation method was 3.10%for AX and 1.99%for VE.The results indicated that the method was precise and reliable.The method has been successfully applied to simultaneous quantification of AX and VE in nutritional supplements products.
基金supported by grants from the Beijing Municipal Public Welfare Development and Reform Pilot Project for Medical Research Institutes(PWD&RPP-MRI,JYY2023-6)the R&D Program of Beijing Municipal Education Commission(KZ20231002543).
文摘Background:Dry eye disease(DED)predominantly results from elevated tear film os-molarity,which can not only cause ocular inconvenience but may lead to visual impair-ments,severely compromising patient well-being and exerting substantial economic burdens as well.Astaxanthin(AST),a member of the xanthophylls and recognized for its robust abilities to combat inflammation and oxidation,is a common dietary sup-plement.Nonetheless,the precise molecular pathways through which AST influences DED are still poorly understood.Methods:Therapeutic targets for AST were identified using data from the GeneCards,PharmMapper,and Swiss Target Prediction databases,and STITCH datasets.Similarly,targets for dry eye disease(DED)were delineated leveraging resources such as the Therapeutic Target Database(TTD),DisGeNET,GeneCards,and OMIM databases,and DrugBank datasets.Interactions among shared targets were charted and dis-played using CytoScape 3.9.0.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted to elucidate the functions of pivotal tar-gets within the protein-protein interaction network.Molecular interactions between AST and key targets were confirmed through molecular docking using AutoDock and PyMOL.Molecular dynamics simulations were performed using GROMACS 2022.3.Viability of human corneal epithelial cells(hCEC)was assessed across varying concen-trations of AST.A mouse model of experimental DED was developed using 0.1%ben-zalkonium chloride(BAC),and the animals were administered 100 mg/kg/day of AST orally for 7 days.The efficacy of the treatments was assessed through a series of di-agnostic tests to evaluate the condition of the ocular surface after the interventions.The levels of inflammation and oxidative stress were quantitatively assessed using methods such as reverse transcription-polymerase chain reaction(RT-PCR),Western blot,and immunofluorescence staining.Results:Network pharmacology suggests that AST may alleviate DED by influenc-ing oxidation-reduction signaling pathways and reducing oxidative stress provoked by BAC.In vivo experiments demonstrated an improved overall condition in AST-administered mice in contrast to the control group.Immunofluorescence staining analyses indicated a decrease in Keap1 protein in the corneal tissues of AST-treated mice and a significant increase in Nrf2 and HO-1 protein.In vitro studies demon-strated that AST significantly enhanced cell viability and suppressed reactive oxy-gen species expression under hyperosmotic(HS)conditions,thereby protecting the human corneal epithelium.Conclusion:AST is capable of shielding mice from BAC-induced DED,decelerating the progression of DED,and mitigating oxidative stress damage under HS conditions in hCEC cells.The protective impact of AST on DED may operate through stimulating the Keap1-Nrf2/HO-1 signaling pathway.Our research findings indicate that AST may be a promising treatment for DED,offering new insights into DED treatment.
基金For financial support,the authors gratefully acknowledge the National Natural Science Foundation of China(U2004164)the National Key Research and Development Program of China(2018YFC1106703)the Key Projects of the Joint Fund of the National Natural Science Foundation of China(U1804251).
文摘The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability.However,excessive degradation rate and the delayed surface endothelialization still limit their further application.In this study,we modified a Mg-Zn-Y-Nd alloy(ZE21B)by preparing MgF_(2) as the corrosion resistance layer,the dopamine polymer film(PDA)as the bonding layer,and hyaluronic acid(HA)loaded astaxanthin(ASTA)as an important layer to directing the cardiovascular cells fate.The electrochemical test results showed that the MgF_(2)/PDA/HA-ASTA coating improved the corrosion resistance of ZE21B.The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation,inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages.Compared with the HAloaded rapamycin(RAPA)coating,our MgF_(2)/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility,indicating stronger multi-functions for the ZE21B alloy on cardiovascular application.
文摘Aim： To evaluate the treatment of male infertility with a strong natural antioxidant, in addition to conventional treatment. Methods： Using a double blind, randomized trial design, 30 men with infertility of ≥12 months and female partners with no demonstrable cause of infertility received conventional treatment according to the guidelines of the World Health Organization （WHO）, and either a strong antioxidant Astaxanthin 16 rag/day （AstaCarox, AstaReal AB, Gustavsberg, Sweden） or placebo for 3 months. The effects of treatment on semen parameters, reactive oxygen species （ROS）, zona-free hamster oocyte test, serum hormones including testosterone, luteinizing hormone （LH）, follicle stimulating hormone （FSH） and Inhibin B, and spontaneous or intrauterine insemination （IUI）-induced pregnancies were evaluated. Results： ROS and Inhibin B decreased significantly and sperm linear velocity increased in the Astaxanthin group （n = 11）, but not in the placebo group （n = 19）. The results of the zona-free hamster oocyte test tended to improve in the Astaxanthin group in contrast with the placebo group, though not reaching statistical significance. The total and per cycle pregnancy rates among the placebo cases （10.5 % and 3.6 %） were lower compared with 54.5 % and 23. 1% respectively in the Astaxanthin group （P=0.028; P=0.036）. Conclusion： Although the present study suggests a positive effect of Astaxanthin on sperm parameters and fertility, the results need to be confirmed in a larger trial before recommending Astaxanthin for the complementary treatment of infertile men. （Asian J Androl 2005 Sep; 7： 257-262）
基金Project supported by the National Natural Science Foundation of China (No. 20702019)the Foundation for Young Professors of Jimei University, China
文摘Optimization of a process for extracting astaxanthin from Phaffia rhodozyma by acidic method was investigated, regarding several extraction factors such as acids, organic solvents, temperature and time. Fractional factorial design, central composite design and response surface methodology were used to derive a statistically optimal model, which corresponded to the following optimal condition： concentration of lactic acid at 5.55 mol/L, ratio of ethanol to yeast dry weight at 20.25 ml/g, temperature for cell-disruption at 30 ℃, and extraction time for 3 min. Under this condition, astaxanthin and the total carotenoids could be extracted in amounts of 1294.7 μg/g and 1516.0 μg/g, respectively. This acidic method has advantages such as high extraction efficiency, low chemical toxicity and no special requirement of instruments. Therefore, it might be a more feasible and practical method for industrial practice.
基金supported by Liao Ning Revitalization Talents Program No. XLYC1807161Dalian High-level Talents Innovation Support Plan No. 2017RQ063+4 种基金Dalian Ocean University Zhanlan scholar ProgramThe National Natural Science Foundation of China under contract Nos. 41206013, 41430963the Public Science and Technology Research Funds Projects of Ocean under contract No. 201205018the National Science and Technology Support Program under contract No. 2014BAB12B02Projects of Institute of Marine Industry Technology of Liaoning Universities
文摘A method for determination of astaxanthin and astaxanthin eaters in shrimp shell by high performance liquid chromatography is established.Shrimp shell are addressed with 5%hydrochloric acid to remove calcium ions.After shell is dried,organics from shrimp shell are extracted with anhydrous ethanol.The alcohol extrative of the shrimp shell is mixed with the ammonium sulfate to extract astaxanthin by aqueous two-phase extraction.The crude astaxanthin is collected,which is distributed in the middle layer of the aqueous two-phase layer.After distilled water is added to the crude astaxanthin,the aqueous solution is centrifuged,and the previous step is repeated for several times.The precipitation in centrifuge tube is collected and dried.The crude astaxanthin dried is dissolved with acetone,and the sample solution is separated by TLC.Every pigment on the TLC plate is collected and dissolved with acetone.The pigments are determined by high performance liquid chromatograph.The results show that aqueous two-phase system,3 mL alcohol extractive of astaxanthin and 4.5 mL 20%ammonium sulfate,can be used to acquire crude astaxanthin.The wavelength of the maximum peak of astaxanthin in ethanol solution is 472 nm.A variety of pigments can be separated from the crude astaxanthin by thin-layer chromatography,including free astaxanthin,astaxanthin monoester,astaxanthin diester,echinenone and other substances.It can be seen from high performance liquid chromatography that the appearance time of free astaxanthin is from 4 min to 5.5 min,and the appearance time of astaxanthin monoester is from 10.5 min to 27.8 min.The method is simple about the sample pretreatment and feasible about the determination of astaxanthin and astaxanthin esters in shrimp shell.
基金Project supported by the National Natural Science Foundation of China (No.30571450)the Foundation for Young Professors of Jimei University of Xiamen,China
文摘Fermentation of Phaffia rhodozyma is a major method for producing astaxanthin, an important pigment with industrial and pharmaceutical application. To improve astaxanthin productivity, single factor and mixture design experiments were used to investigate the effects of nitrogen source on Phaffia rhodozyma cultivation and astaxanthin production. Results of single factor experiments showed nitrogen source could significantly affect P. rhodozyma cultivation with respect to carbon source utilization, yeast growth and astaxanthin accumulation. Further studies of mixture design experiments using (NH4)2SO4, KNO3 and beef extract as nitrogen sources indicated that the proportion of three nitrogen sources was very important to astaxanthin production. Validation experiments showed that the optimal nitrogen source was composed of 0.28 g/L (NH4)2SO4, 0.49 g/L KNO3 and 1.19 g/L beef extract. The kinetic characteristics of batch cultivation were investigated in a 5-L pH-stat fermentor. The maximum amount of biomass and highest astaxanthin yield in terms of volume and in terms of biomass were 7.71 mg/L and 1.00 mg/g, respectively.
基金Supported by the Xiamen Scientific and Technologic Projects(XSTP)(Nos.3052Z20031086,3052Z20123004)the project of Xiamen Southern Ocean Technology Center of China(No.14CZP035HJ09)+2 种基金partly funded by the Marine Science Base Scientific Research Training and Scientific Research Ability Enhancement Project of Xiamen University(No.J1210050)the National Marine Commonweal Research Program,China(No.201205020-2)the XMU Training Program of Innovation and Enterpreneurship for Undergraduates(No.2016X0619)
文摘An algal astaxanthin feeding trial was carried out to investigate the ef fects of natural astaxanthin from Haematococcus pluvialis as feed additives on growth, pigmenting efficacy and antioxidant capacity in blood parrot(C ichlasoma citrinellum × C ichlasoma. synspilum). Tissue total antioxidant capacity(TAC), superoxide dismutase(SOD), catalase(CAT) and maleic dialdehyde(MDA) were chosen as measures of its antioxidant capacity. All fish which received an astaxanthin(from micro-algal H. pluvialis) supplemented diet with 400 mg/kg of astaxanthin, after 50 days of feeding, the astaxanthin-fed fish displayed a pinkcolored skin and the control-fed fish displayed a grayish skin. For the growth, the weight gains of controlfed fish and astaxanthin-fed fish were 200% and 300%, respectively. Samples of skin and scales were used for analysis of total carotenoids and astaxanthin content, and fish feeding astaxanthin showed significantly( P <0.05) higher concentrations than the control group, indicating that the pigmentation of this fish had been significantly improved by dietary astaxanthin. Compared with the control fish, pigmented fish had lower SOD, CAT and MDA and higher TAC. It can be concluded that supplementation with dietary astaxanthin could eff ectively enhance growth, skin coloration and the antioxidant capacity of this fish. This study will provide a reference for application of natural astaxanthin from H. pluvialis as feed additives in blood parrot artificial breeding. Our data is also useful in ornamental fish farming, especially when the retentivity of astaxanthin in the skin and scales are involved. It is leading to the possibility of increasing the pigmentation of farmed-fish by adding the powdered form of H. pluvialis to the diet as an ef fective pigment.
基金Supported by the Yunnan Provincial Sciences and Technology Department,China(No.2007AD009)the National Natural Science Foundation of China(No.31272680)the Ministry of Science and Technology of China(No.2013AA065805)
文摘In this paper,we investigated the effects of temperature,oxygen,antioxidants,and corn germ oil on the stability of astaxanthin from Haematococcus pluvialis under different storage conditions,and changes in the composition of astaxanthin esters during storage using high performance liquid chromatography and spectrophotometry.Oxygen and high temperatures(22–25°C) significantly reduced the stability of astaxanthin esters.Corn germ oil and antioxidants(ascorbic acid and vitamin E)failed to protect astaxanthin from oxidation,and actually significantly increased the instability of astaxanthin.A change in the relative composition of astaxanthin esters was observed after 96 weeks of long-term storage.During storage,the relative amounts of free astaxanthin and astaxanthin monoesters declined,while the relative amount of astaxanthin diesters increased.Thus,the ratio of astaxanthin diester to monoester increased,and this ratio could be used to indicate if astaxanthin esters have been properly preserved.If the ratio is greater than 0.2,it suggests that the decrease in astaxanthin content could be higher than 20%.Our results show that storing algal powder from H.pluvialis or other natural astaxanthin products under vacuum and in the dark below 4°C is the most economical and applicable storage method for the large-scale production of astaxanthin from H.pluvialis.This storage method can produce an astaxanthin preservation rate of at least 80%after 96 weeks of storage.
基金Supported by the Fundamental Research Funds for the Central Universities （FRF-AS-10-001B） and the National Natural Science Foundation of China （11071013）.
文摘method of extracting astaxanthin from Phaffia rhodozyma with various solvents after acid washing was investigated. The extraction efficiency was distinctly increased after acid washing of P. rhodozyma cells. When the concentration of HCl was 0.4 mol.L^-1, the highest extraction efficiency of astaxanthin was achieved which was about three times higher than the control. Acetone or benzene as single polar or non-polar solvent was the most ef- fective solvent in our research. With a combination of isopropanol and n-hexane （volume ratio of 2 ： 1）, the maxi- mal extraction efficiency was achieved, approximately 60% higher than that obtained with a single solvent. The liquid-solid ratio and the extracting time were also optimized. Under the optimum extraction conditions, the extraction yield of astaxanthin exceeded 98%.
基金Supported by the National Natural Science Foundation of China(No.31572638)the Public Benefit Program of Zhejiang Science and Technology Department(No.2015C32021)+4 种基金the Program of Ningbo Science and Technology Bureau(No.2014C10023)the NSF of Ningbo Government(No.2015A610265)the Project of Science and Technology Innovation for College Students in Zhejiang Province(No.2016R405078)the K.C.Wong Magna Fund in Ningbo Universitythe Subject Project of Ningbo University(No.xkl1526)
文摘The optimum concentration of Na_2 WO_4 was explored in relation to the cell density and astaxanthin content in Haematococcus pluvialis. Then, the cellular morphology, nitrate reductase(NR) activity, soluble sugar and protein contents, and chlorophyll ?uorescence were measured, and the transcriptional expression of carotenogenic genes was determined by quantitative real-time PCR. The results showed that 3.0 mmol/L of Na_2 WO_4 was the optimum concentration to induce astaxanthin accumulation, with a maximum content of 49.41±0.13 pg/cell reached on the tenth day. The NR activity decreased signi?cantly and continually after Na_2 WO_4 treatment. The soluble sugar content increased gradually during the experimental period and was eventually signi?cantly higher than that in the control. The soluble protein content increased rapidly,reached a maximum in day 0.5 and day 1 and then decreased. The ef fective photochemical effciency of PSII( F v'/F m') and light saturation( E k) ?rst decreased and then tended to stabilize, and NADP +-glyceraldehyde-3-phosphate dehydrogenase(GAPDH) gene expression was correlated with photosynthesis. The transcriptional expression of ipi, psy and bkt was signi?cantly increased compared with that in the control after application of Na_2 WO_4, and the relative expression of ipi reached the highest level on the ?fth day, with a 98.03±1.92-fold increase. Our results describe a new approach to promote the ef fective accumulation of astaxanthin in H. pluvialis by NR inhibitor Na_2 WO_4.
基金Project (No. 20276064) supported by the National Natural Science Foundation of China
文摘A derivative ratio spectrophotometric method was used for the simultaneous determination of β-carotene and astaxanthin produced from Phaffia rhodozyma. Absorbencies of a series of the standard carotenoids in the range of 441 nm to 490 nm demonstrated that their absorptive spectra accorded with Beer’s law and that the additivity when the concentrations of β-carotene and astaxanthin and their mixture were within the range of 0 to 5 μg/ml, 0 to 6 μg/ml, and 0 to 6 μg/ml, respectively. When the wavelength interval (?λ) at 2 nm was selected to calculate the first derivative ratio spectra values, the first derivative amplitudes at 461 nm and 466 nm were suitable for quantitatively determining β-carotene and astaxanthin, respectively. Effect of divisor on derivative ratio spectra could be neglected; any concentration used as divisor in range of 1.0 to 4.0 μg/ml is ideal for calculating the derivative ratio spectra values of the two carotenoids. Calibration graphs were established for β-carotene within 0?6.0 μg/ml and for astaxanthin within 0?5.0 μg/ml with their corresponding regressive equations in: y=?0.0082x?0.0002 and y=0.0146x?0.0006, respectively. R-square values in excess of 0.999 indicated the good linearity of the calibration graphs. Sample recovery rates were found satisfactory (>99%) with relative standard deviations (RSD) of less than 5%. This method was suc- cessfully applied to simultaneous determination of β-carotene and astaxanthin in the laboratory-prepared mixtures and the extract from the Phaffia rhodozyma culture.
基金supported by the National Key R&D Program of China (No. 2019YFA0905700)the National Natural Science Foundation of China (No. 31870058)。
文摘This study engineered β-carotene ketolase CrtW and β-carotene hydroxylase CrtZ to improve biosynthesis of astaxanthin in Escherichia coli. Firstly, crtW was randomly mutated to increase CrtW activities on conversion from β-carotene to astaxanthin. A crtW* mutant with A6 T, T105 A and L239 M mutations has improved 5.35-fold astaxanthin production compared with the wild-type control. Secondly, the expression levels of crtW* and crtZ on chromosomal were balanced by simultaneous modulation RBS regions of their genes using RBS library. The strain RBS54 selected from RBS library, directed the pathway exclusively towards the desired product astaxanthin as predominant carotenoid(99%). Lastly, the number of chromosomal copies of the balanced crtW*-crtZ cassette from RBS54 was increased using a Cre-loxP based technique, and a strain with 30 copies of the crtW*-crtZ cassette was selected. This final strain DL-A008 had a 9.8-fold increase of astaxanthin production compared with the wild-type control. Fed-batch fermentation showed that DL-A008 produced astaxanthin as predominant carotenoid(99%) with a specific titer of 0.88 g·L^(-1) without addition of inducer. In conclusion, through constructing crtW mutation, balancing the expression levels between crtW* and crtZ, and increasing the copy number of the balanced crtW*-crtZ cassette, the activities of β-carotene ketolase and β-carotene hydroxylase were improved for conversion of β-carotene to astaxanthin with higher efficiency. The series of conventional and novel metabolic engineering strategies were designed and applied to construct the astaxanthin hetero-producer strain of E. coli, possibly offering a general approach for the construction of stable hetero-producer strains for other natural products.
