Astaxanthin Production Research Articles

Effect of spent coffee grounds extract on astaxanthin production by Xanthophyllomyces dendrorhous

The world generates a large amount of used coffee grounds every day. These spent coffee grounds could potentially be used to cultivate microorganisms for fine chemical productions. Here, the effect of spent coffee grounds extract (SCGE) on astaxanthin-producing yeast, Xanthophyllomyces dendrorhous was explored. The SCGE addition to the culture medium notably increased growth of cell and decreased intracellular astaxanthin (ASX) content. The caffeine contained in SCGE was found to activate ASX biosynthesis, not to effect on cell growth. In X. dendrorhous, the addition of SCGE resulted in significant cell growth, and the addition of caffeine contained therein suppressed the decrease in ASX biosynthesis, resulting in an overall increase in ASX production.

Role of Autophagy in Haematococcus lacustris Cell Growth under Salinity.

The microalga Haematococcus lacustris (formerly H. pluvialis) is able to accumulate high amounts of the carotenoid astaxanthin in the course of adaptation to stresses like salinity. Technologies aimed at production of natural astaxanthin for commercial purposes often involve salinity stress; however, after a switch to stressful conditions, H. lacustris experiences massive cell death which negatively influences astaxanthin yield. This study addressed the possibility to improve cell survival in H. lacustris subjected to salinity via manipulation of the levels of autophagy using AZD8055, a known inhibitor of TOR kinase previously shown to accelerate autophagy in several microalgae. Addition of NaCl in concentrations of 0.2% or 0.8% to the growth medium induced formation of autophagosomes in H. lacustris, while simultaneous addition of AZD8055 up to a final concentration of 0.2 µM further stimulated this process. AZD8055 significantly improved the yield of H. lacustris cells after 5 days of exposure to 0.2% NaCl. Strikingly, this occurred by acceleration of cell growth, and not by acceleration of aplanospore formation. The level of astaxanthin synthesis was not affected by AZD8055. However, cytological data suggested a role of autophagosomes, lysosomes and Golgi cisternae in cell remodeling during high salt stress.

An MIQP framework for metabolic pathways optimisation and dynamic flux analysis

Dynamic flux analysis methods have been widely used for deciphering complex metabolic fluxes transients. However, many of them require frequent experimental measurements and are ineffective in dealing with under-determined metabolic reaction networks. In this study, we addressed these challenges by (i) integrating a macroscale kinetic model with its dynamic metabolic flux model to enable flux simulation over the entire time course for batch operation, and (ii) constructing a single-level mixed-integer quadratic program (MIQP) to automatically identify the shortest metabolic pathways from substrate inflow to biosynthesis of biomass and desired bioproducts. To demonstrate the advantages of the proposed framework, a X. dendrorhous fermentation process for astaxanthin production was utilised as the case study. It is found that the current framework is able to efficiently identify essential pathways and reduce the size of the original metabolic network by 70% with negligible computational cost. Furthermore, the modelling consistency, robustness, and limitation of this framework were thoroughly investigated. This research provides a new avenue for efficient in-silico design, analysis, and gene knockout of microbial strains for bioproduct synthesis.

Direct production of astaxanthin from food waste by Phaffia rhodozyma

Bioconversion of food waste (FW) into value-added products is a promising approach to solve FW management problem and achieve the global goal of carbon peak and carbon neutralization. In this study, FW could be used as a complete medium to compare the effects of four different fermentation strategies on direct astaxanthin fermentation by Phaffia rhodozyma. The carotenoid production by direct fermentation (DF) reached 129.5 mg/L, increasing by 61.3 %, compared with separate hydrolysis and fermentation (SHF), and carotenoid production by simultaneous saccharification fermentation (SSF) and 1 h pre-hydrolysis SSF (PSSF) were only 20.2 % and 21.5 % higher than DF, respectively. The mechanism of astaxanthin production in the DF could be attributed to the utilization of rice starch due to the production of amylase, and the stimulation of cell growth resulted from the metal elements and the lipid of soybean oil in FW. Remarkably, a 70.3 % increase of carotenoid production was observed when substrate loading increased from 10 % to 20 %. The present study provides a novel process for astaxanthin production from direct bioconversion of FW by P. rhodozyma, which shows potential for low-cost industrial production of astaxanthin.

Astaxanthin accumulation in Microcystis aeruginosa under different light quality

The aim of this work was to uncover the astaxanthin biosynthesis mechanism in Microcystis aeruginosa under optimum light quality, and promote astaxanthin production using this alga. Among purple, blue and red light, only purple light promoted M. aeruginosa cell growth compared with white light, due to up-regulating expression of the genes related with DNA replication. An increase was detected in the photosynthetic rate under purple light, which should be caused by the raised carotenoid content and up-regulation of the genes associated with light reaction and carbon fixation. Compared with white light, purple light increased the levels of β-carotene, zeaxanthin and astaxanthin by up-regulating expression of the genes related with methylerythritol-4-phosphate pathway (MEP) and astaxanthin biosynthesis. For red and blue light, they did not impact or declined the content of astaxanthin and its precursors. Therefore, purple light promoted M. aeruginosa cell growth and astaxanthin production by up-regulating related gene expression.

The role of key genes in astaxanthin biosynthesis in Phaffia rhodozyma by transcript level and gene knockout

Phaffia rhodozyma is a potential industrial source of natural astaxanthin. Dicyclic and monocyclic pathways of carotenoid synthesis are important nodes in Phaffia rhodozyma, but the relationship between the two pathways and astaxanthin production remains unclear. Eight genes related to dicyclic and monocyclic pathways in three different strains of P. rhodozyma were analysed, and the relationship between expression and astaxanthin biosynthesis was explored. Among these genes, CRTS genes (R = 0.69, P < 0.05) and CRTYB (R = 0.75, P < 0.05) showed the closest correlations with carotenoid and astaxanthin biosynthesis, respectively. To further study these relationships in detail, the CRTYB and CRTS genes were knocked out by homologous recombination. After CRTYB knockout, astaxanthin was decreased to an undetectable level. This result suggested that CRTYB plays a role in dicyclic and monocyclic pathways. Meanwhile, the CRTS gene was in the dicyclic pathway of astaxanthin biosynthesis, and its knockout promoted the monocyclic pathway and resulted in a 25 % increase in astaxanthin production at 120 h. The possible rate-limiting enzymes were the enzymes encoding CRTS and CRTYB by regression analysis. Knockout of the CRTS and CRTYB genes was helpful in understanding the synthetic pathway of astaxanthin and significant to the industrial application of astaxanthin production.

Critical assessment of the filamentous green microalga Oedocladium carolinianum for astaxanthin and oil production

The filamentous microalga Oedocladium carolinianum that was isolated from soil was found to be capable of producing large amounts of astaxanthin under stress culture conditions. When the culture conditions were optimized, the maximum specific growth rate of 0.37 d−1 and the maximum biomass concentration of 10.12 g L−1 were obtained after 18 days of cultivation in 1-liter glass columns (inner diameter: 5 cm) under laboratory conditions. When subjected to culture conditions of nitrogen starvation and 2 g L−1 NaCl-induced salinity stress, however, the cells produced up to 3.91% w/w astaxanthin and a high astaxanthin productivity of 24.2 mg L−1 d−1 was obtained. Analysis by HPLC-MS revealed that the majority of astaxanthin was in fatty acid esterified forms with a typical molecular ratio of free, monoester and diester astaxanthin of 1:18:81. The biosynthesis of astaxanthin coincided with that of fatty acids, and the total fatty acid content reached 40% w/w or more. The technical feasibility of mass culture of O. carolinianum was tested in a 7000-L inclined thin-layer photobioreactor and a 10,000-L tubular photobioreactor in a greenhouse. This demonstrated that O. carolinianum grew rapidly in a nitrogen replete BG-11 culture medium and the maximum biomass concentrations obtained in the inclined thin-layer photobioreactor and tubular photobioreactor were 3.74 g L−1 and 3.07 g L−1 respectively, resulting in maximum biomass productivities of 276 mg L−1 d−1 and 198 mg L−1 d−1, respectively. Although small populations of a few zooplankton species occurred in the two types of photobioreactors, none grazed on O. carolinianum and they grazed on invading unicellular microalgae instead. It was therefore concluded that O. carolinianum is a promising microalga for sustainable co-production of astaxanthin and fatty acids.

Transcriptomic and Proteomic Characterizations of the Molecular Response to Blue Light and Salicylic Acid in Haematococcus pluvialis

Haematococcus pluvialis accumulates a large amount of astaxanthin under various stresses, e.g., blue light and salicylic acid (SA). However, the metabolic response of H. pluvialis to blue light and SA is still unclear. We investigate the effects of blue light and SA on the metabolic response in H. pluvialis using both transcriptomic and proteomic sequencing analyses. The largest numbers of differentially expressed proteins (DEPs; 324) and differentially expressed genes (DEGs; 13,555) were identified on day 2 and day 7 of the treatment with blue light irradiation (150 μmol photons m−2s−1), respectively. With the addition of SA (2.5 mg/L), a total of 63 DEPs and 11,638 DEGs were revealed on day 2 and day 7, respectively. We further analyzed the molecular response in five metabolic pathways related to astaxanthin synthesis, including the astaxanthin synthesis pathway, the fatty acid synthesis pathway, the heme synthesis pathway, the reactive oxygen species (ROS) clearance pathway, and the cell wall biosynthesis pathway. Results show that blue light causes a significant down-regulation of the expression of key genes involved in astaxanthin synthesis and significantly increases the expression of heme oxygenase, which shows decreased expression by the treatment with SA. Our study provides novel insights into the production of astaxanthin by H. pluvialis treated with blue light and SA.

Development of an Efficient Gene Editing Tool in Schizochytrium sp. and Improving Its Lipid and Terpenoid Biosynthesis.

Schizochytrium sp. HX-308 is a marine microalga with fast growth and high lipid content, which has potential as microbial cell factories for lipid compound biosynthesis. It is significant to develop efficient genetic editing tool and discover molecular target in Schizochytrium sp. HX-308 for lipid compound biosynthesis. In this study, we developed an efficient gene editing tool in HX-308 which was mediated by Agrobacterium tumefaciens AGL-1. Results showed that the random integration efficiency reached 100%, and the homologous recombination efficiency reached about 30%. Furthermore, the metabolic pathway of lipid and terpenoid biosynthesis were engineered. Firstly, the acetyl-CoA c-acetyltransferase was overexpressed in HX-308 with a strong constitutive promoter. With the overexpression of acetyl-CoA c-acetyltransferase, more acetyl-CoA was used to synthesize terpenoids, and the production of squalene, β-carotene and astaxanthin was increased 5.4, 1.8, and 2.4 times, respectively. Interestingly, the production of saturated fatty acids and polyunsaturated fatty acids also changed. Moreover, three Acyl-CoA oxidase genes which catalyze the first step of β-oxidation were knocked out using homologous recombination. Results showed that the production of lipids increased in the three knock-out strains. Our results demonstrated that the A. tumefaciens-mediated transformation method will be of great use for the study of function genes, as well as developing Schizochytrium sp. as a strong cell factory for producing high value products.

Enhancement of astaxanthin accumulation in Haematococcus pluvialis by exogenous oxaloacetate combined with nitrogen deficiency

Effective inducers and stress conditions play an essential role in the regulation of astaxanthin biosynthesis. This study reports a strategy developed by combining exogenous addition of oxaloacetate (OA) with nitrogen deficiency to facilitate astaxanthin production in Haematococcus pluvialis. Significantly, addition of 10 mM-OA enhanced the cellular astaxanthin content about 7.18-fold under nitrogen deficiency on day 7, with the content of astaxanthin esters increased concomitantly. To further elucidate the role and mechanism of OA on astaxanthin synthesis, the physiological and metabolic analyses of H. pluvialis treated with exogenous OA were performed. The results showed that exogenous OA promoted respiration over photosynthesis. Concurrently, the metabolite levels in the Embden-Meyerhof-Parnas pathway, pentose phosphate pathway and tricarboxylic acid cycle obviously increased. The enhancement of respiratory metabolic pathways led to elevated levels of substrates, thus directly promoted astaxanthin synthesis. The present findings provide a new and effective approach for optimizing astaxanthin production.

Haematococcus pluvialis Accumulated Lipid and Astaxanthin in a Moderate and Sustainable Way by the Self-Protection Mechanism of Salicylic Acid Under Sodium Acetate Stress.

To elucidate the mechanism underlying increased fatty acid and astaxanthin accumulation in Haematococcus pluvialis, transcriptome analysis was performed to gain insights into the multiple defensive systems elicited by salicylic acid combined with sodium acetate (SAHS) stresses with a time course. Totally, 112,886 unigenes and 61,323 non-repeat genes were identified, and genes involved in carbon metabolism, primary and secondary metabolism, and immune system responses were identified. The results revealed that SA and NaAC provide both energy and precursors to improve cell growth of H. pluvialis and enhance carbon assimilation, astaxanthin, and fatty acids production in this microalga with an effective mechanism. Interestingly, SA was considered to play an important role in lowering transcriptional activity of the fatty acid and astaxanthin biosynthesis genes through self-protection metabolism in H. pluvialis, leading to its adaption to HS stress and finally avoiding massive cell death. Moreover, positive correlations between 15 key genes involved in astaxanthin and fatty acid biosynthesis pathways were found, revealing cooperative relation between these pathways at the transcription level. These results not only enriched our knowledge of the astaxanthin accumulation mechanism in H. pluvialis but also provided a new view on increasing astaxanthin production in H. pluvialis by a moderate and sustainable way in the future.

Enhancement of astaxanthin production in Schizochytrium limacinum B4D1 under ethanol induction

Schizochytrium limacinum is one of the most extensively studied marine algae for production of docosahexaenoic acid (DHA) which is a type of omega-3 fatty acid important for brain development and human health. This microorganism has shown significant potential for carotenoid production, i.e., astaxanthin. In this study, we have investigated the effects of different ethanol concentrations on the production of astaxanthin in S. limacinum B4D1. We have also characterized a series of physiological and biological properties (i.e., biomass, lipid content, and fatty acid composition) to explore the metabolic mechanisms of astaxanthin production in S. limacinum B4D1 induced by ethanol. Results have shown that high concentration of ethanol (≥3%) promotes the accumulation of astaxanthin and alters the proportion of fatty acids. In order to explore the molecular mechanisms causing these changes, we detected the expression levels of genes involved in astaxanthin synthesis pathway and competitive pathways using quantitative real-time PCR technology. Results showed that ethanol significantly enhanced transcriptional expression of five genes (HMGR, MK, GGPS, crtIBY, and crtZ) responsible for biosynthesis of astaxanthin and decreased expression of two genes (ACACA and FDFT1) involved in competitive pathways. We further evaluated the expression of three genes (SOD, CAT, and APX) inhibiting the production of reactive oxygen species (ROS). Results showed that the transcription levels of these three genes were significantly increased by ethanol with various concentrations. Our study has demonstrated that ethanol is an effective inducer to promote astaxanthin accumulation in S. limacinum B4D1.

The effective astaxanthin productivities of immobilized Haematococcus pluvialis with bacterial cellulose

Haematococcus pluvialis is traditionally cultivated in a suspension for astaxanthin production. This study presents the novel cultivation approach by immobilized H. pluvialis in bacterial cellulose (BC) produced from the symbiosis of Gluconacetobacter xylinus and H. pluvialis. It was observed that the immobilization itself was a regulator to increase the astaxanthin content. The key genes associated to astaxanthin synthesis, such as psy, lcy, bkt, chy, were significantly up-regulated after immobilization. BC immobilized gel can be utilized concurrently with different technologies to improve astaxanthin accumulation (e.g., amount of induction medium, area of biogel, et al). A small-scale screen panel photobioreactor was design to explore the application of the cultivation approach. Compared to suspended culture, the induction time was shortened from 7 days to 3 days. Astaxanthin productivity of red stage reached 343.2 mg·m−2·d−1. This was greater than that of many other cultivation systems.

Evidence for hybrid breakdown in production of red carotenoids in the marine invertebrate Tigriopus californicus.

The marine copepod, Tigriopus californicus, produces the red carotenoid pigment astaxanthin from yellow dietary precursors. This 'bioconversion' of yellow carotenoids to red is hypothesized to be linked to individual condition, possibly through shared metabolic pathways with mitochondrial oxidative phosphorylation. Experimental inter-population crosses of lab-reared T. californicus typically produces low-fitness hybrids is due in large part to the disruption of coadapted sets nuclear and mitochondrial genes within the parental populations. These hybrid incompatibilities can increase variability in life history traits and energy production among hybrid lines. Here, we tested if production of astaxanthin was compromised in hybrid copepods and if it was linked to mitochondrial metabolism and offspring development. We observed no clear mitonuclear dysfunction in hybrids fed a limited, carotenoid-deficient diet of nutritional yeast. However, when yellow carotenoids were restored to their diet, hybrid lines produced less astaxanthin than parental lines. We observed that lines fed a yeast diet produced less ATP and had slower offspring development compared to lines fed a more complete diet of algae, suggesting the yeast-only diet may have obscured effects of mitonuclear dysfunction. Astaxanthin production was not significantly associated with development among lines fed a yeast diet but was negatively related to development in early generation hybrids fed an algal diet. In lines fed yeast, astaxanthin was negatively related to ATP synthesis, but in lines fed algae, the relationship was reversed. Although the effects of the yeast diet may have obscured evidence of hybrid dysfunction, these results suggest that astaxanthin bioconversion may still be related to mitochondrial performance and reproductive success.

Techno-economic analysis of a new downstream process for the production of astaxanthin from the microalgae Haematococcus pluvialis

The biotechnological production of the carotenoid astaxanthin is done with the microalgae Haematococcus pluvialis (H. pluvialis). Under nutrient deficiency and light stress, H. pluvialis accumulates astaxanthin intracellularly and forms a resistant cyst cell wall that impedes direct astaxanthin extraction. Therefore, a complex downstream process is required, including centrifugation, mechanical cell wall disruption, drying, and supercritical extraction of astaxanthin with CO2. In this work, an alternative downstream process based on the direct extraction of astaxanthin from the algal broth into ethyl acetate using a centrifugal partition extractor (CPE) was developed. A mechanical cell wall disruption or germination of the cysts was carried out to make astaxanthin accessible to the solvent. Zoospores containing astaxanthin are released when growth conditions are applied to cyst cells, from which astaxanthin can directly be extracted into ethyl acetate. Energy-intensive unit operations such as spray-drying and extraction with supercritical CO2 can be replaced by directly extracting astaxanthin into ethyl acetate. Extraction yields of 85% were reached, and 3.5 g of oleoresin could be extracted from 7.85 g homogenised H. pluvialis biomass using a CPE unit with 244 mL column volume. A techno-economic analysis was done for a hypothetical H. pluvialis production facility with an annual biomass output of 8910 kg. Four downstream scenarios were examined, comparing the novel process of astaxanthin extraction from homogenised cyst cells and germinated zoospores via CPE extraction with the conventional industrial process using in-house or supercritical CO2 extraction via an external service provider. After 10 years of operation, the highest net present value (NPV) was determined for the CPE extraction from germinated zoospores.

A strategy for promoting carbon flux into fatty acid and astaxanthin biosynthesis by inhibiting the alternative oxidase respiratory pathway in Haematococcus pluvialis

In the present study, the mechanisms for facilitating fatty acid and astaxanthin biosynthesis-related processes by inhibiting the alternative oxidase (AOX) respiratory pathway in Haematococcus pluvialis was investigated. The restriction of the AOX pathway induced the accumulation of reactive oxygen species, NAD(P)H and its substrates (acetyl-CoA, pyruvate and glyceraldehy-3-phosphate), which are required for fatty acid and astaxanthin production, thereby promoting the carbon flux into fatty acid and astaxanthin biosynthesis. During a 9-day incubation period, the fatty acid and astaxanthin contents increased by 20.6% and 20.7%, respectively, when the AOX pathway was inhibited approximately 37.7%. The AOX pathway may be inhibited by nutrient (nitrogen and phosphorus) removal, inhibitor addition and air/CO2 aeration adjustments in the large-scale cultivation of H. pluvialis. Therefore, the current study provides a useful enhancement strategy for fatty acid and astaxanthin coproduction and elucidates the roles of the AOX pathway in regulating fatty acid and astaxanthin biosynthesis.

Determinants of astaxanthin industrial-scale production under stress caused by light photoperiod management of Haematococcus pluvialis cultivation

Haematococcus pluvialis (Chlorophyta) is a microalga with the greatest capacity to generate pure natural astaxanthin with powerful antioxidant properties, through special cysts, in response to disruptions caused by stress conditions. This research tested the design of a prototype for applying artificial light photoperiods controlled by light-emitting diodes on an industrial scale for generating forced stress in H. pluvialis cells during two seasons of the year (winter and spring 2019) in the Coquimbo region in Chile. Three different culture structures were used for the four stages of the alga production cycle. Two containers, A and B, were used for the first and second culture stages, while a raceway (large pool) was used for the third and fourth culture stages. Experiments with four different photoperiods (PP) that represent hours of light:darkness were conducted in two trials (spring 16:8 and winter 18:6) and two for control (spring 11:13 and winter 10:14). In the experiment, an exponential increase of β-carotenoid was achieved, used in human and animal food for its health properties and as a natural colorant in the salmonids industry. Biomass and astaxanthin production under forced stress were measured with physical and chemical variables such as light intensity, temperature, pH, and dissolved oxygen. Results show that the spring culture showed a considerable increase of cysts and, therefore, of astaxanthin reservoirs, reaching a pigment production density of 276 g m -3 , with the consequent increase in density of up to 22% more than the control PP.

Multifaceted strategies for economic production of microalgae Haematococcus pluvialis-derived astaxanthin via direct conversion of CO2

Owing to its strong antioxidant properties, astaxanthin has a high market price in the nutraceutical and pharmaceutical fields, and its demand is increasing. Furthermore, with an increase in the demand for green technology, astaxanthin production through direct CO2 conversion using the autotrophic green microalga Haematococcus pluvialis as a bio-platform has received much attention. Large-scale outdoor cultivation of H. pluvialis using waste CO2 sources and sunlight can secure sustainability and improve economic efficiency. However, low strain performance, reduced light utilization because of increased cell density, and inefficient transfer of gaseous CO2 into liquid culture broth hinder its large-scale commercialization of astaxanthin. Herein, we presented a multifaceted strategy, including the development of high-efficiency strains, a culture system for astaxanthin accumulation, and astaxanthin extraction from biomass, for economically producing astaxanthin from H. pluvialis through direct CO2 conversion. Future perspectives were presented by comparing and analyzing various previous studies conducted using the latest technology.

Sodium chloride stimulates the biomass and astaxanthin production by Haematococcus pluvialis via a two-stage cultivation strategy

A major challenge facing by astaxanthin industrialization is the low productivity and high production costs. This study established a two-stage cultivation strategy based on the application of NaCl to improve the production of biomass and astaxanthin by Haematococcus pluvialis. During the first growth stage, 12.5 mg L-1 NaCl led to a remarkable enhancement in biomass, which was 1.28 times compared with the control. Moreover, 2 g L-1 NaCl stimulated the astaxanthin content from 12.18 mg g−1 to 25.92 mg g−1 during the second induction stage. Simultaneously, salinity stress application increased the lipids and GABA contents, as well as the levels of Ca2+ and carotenogenic genes’ expression, but suppressed the contents of carbohydrate and protein and high-light induced-ROS. This study proposed a simple and convenient strategy for efficient coproduction of biomass and astaxanthin and provides insights into the underlying mechanism of astaxanthin biosynthesis in H. pluvialis induced by salinity stress.

Rice Straw Hydrolysis and Cultivation of Xanthophyllomyces dendrorhous for Astaxanthin Production and Antioxidant Properties

Astaxanthin is a natural pigment with strong antioxidant activity and is widely supplied as dietary supplement. The red yeast Xanthophyllomyces dendrorhous is one of the potential sources for astaxanthin production. Rice straw was considered for utilization on cultivation and astaxanthin production. Rice straw was treated by autoclave-assisted alkaline pretreatment. and hydrolyzed by cellulase hydrolysis. X. dendrorhous TISTR5730 was cultured and accumulated as the astaxanthin on rice straw hydrolysate. The highest reducing sugar concentration of rice straw hydrolysate was 89.82±0.39g/L (0.71±0.01g/g) when using rice straw (3.3%) and cellulase loading (3 mL). High cell density X. dendrohous TISTR5730 cultivation on rice straw hydrolysate with 20 and 40 g/L of initial reducing sugar was investigated. 40 g/L was appropriate for biomass production while 20 g/L was suitable for astaxanthin accumulation. The highest astaxanthin content was 417.28±50.89 μg/g cell basis at 192 h. Astaxanthin productivity and yield coefficient were 0.01±0.00 mg/L/h and 0.11±0.01 mg/g sugar consumed. The antioxidant activities of astaxanthin were determined by DPPH and ABTS scavenging and FRAP reducing power. The produced astaxanthin represented the high antioxidant activities with IC50 of 9.30 and 1.67 μg/mL of DPPH and ABTS scavenging respectively and FRAP reducing power of 5.31±0.07 μg TEAC/mL. This research indicated that rice straw hydrolysate could be an alternative medium for astaxanthin production. Antioxidant activity of astaxanthin was proved and was feasible for further applications.