Total Carotenoid Yield Research Articles

Effect of different ultrasound conditions and other parameters on solids gain, water loss, and properties of osmotically dehydrated carrots

AbstractOsmotic dehydration (OD) of carrots was studied by varying the OD conditions (ultrasound as pretreatment [USP], ultrasound‐assisted OD [USOD], and OD without ultrasound [no treatment]), solute concentration (50, 60, and 70°Brix) and solid‐to‐solution ratio (1:3, 1:4, and 1:5). The osmotically dehydrated carrots obtained from the different combinations were then analyzed for solid‐gain (SG) and water loss. Color and texture measurements along with carotenoid content were also studied. Among the different solid‐to‐solution ratios (1:3, 1:4, and 1:5), samples dehydrated with 1:4 yielded the best result for different tests. USOD samples (1:4) gave significantly (p < 0.05) better results for water‐loss (68.74%) and SG (16.57%) as compared to SG of USP (12.46%) and SG of non‐treated samples (11.6%). USOD samples underwent the least amount of color change but had significantly higher values of hardness (240.38 N) than other treatments. The yield of total carotenoids was also significantly (p < 0.05) higher in the USOD samples (22.30 mg/100 g) when compared with USP (18.27 mg/100 g) and non‐treated samples (13.94 mg/100 g). The better quality of products from USOD treatment in terms of color, texture, and nutrition can make it a popular choice in the food industry for various applications.Practical applicationsOsmotic dehydration (OD) is a useful technique to preserve the nutritional and sensory qualities of carrots and extend its shelf life. OD is a time‐consuming process and the rate of mass transfer from foods can be increased when OD is combined with other processes. Ultrasound (US) processing is a non‐thermal process that can be used to increase the mass transfer rate during the OD process. In the present work, US was applied as a pretreatment before carrying out the OD process and during the OD process, that is, US was applied in the osmotic solution after putting the carrot slices to see which method was better in increasing the mass transfer rate and preserving the quality of the dehydrated carrots. The findings will help in deciding the proper way for US to be applied for the OD process for carrots and can be extended to other fruits and vegetables.

Utilization of olive mill wastewater for selective production of lipids and carotenoids by Rhodotorula glutinis.

Olive mill wastewater (OMW) is a zero-cost substrate for numerous value-added compounds. Although several studies on the production of lipids and carotenoids by Rhodotorula glutinis in OMW exist, none of them has specifically focused on the conditions for a target lipid or carotenoid. This study presents cultivation conditions that selectively stimulate the cell biomass, individual carotenoids and lipids. It was found that supplemental carbon and nitrogen sources as well as illumination affected cell biomass the most. High temperature, low initial pH, illumination, lack of urea and presence of glycerol stimulated the lipid synthesis. The highest total lipid content obtained in undiluted OMW supplemented with urea was 11.08 ± 0.17% (w/w) whilst it was 41.40 ± 0.21% (w/w) when supplemented with glycerol. Moreover, the main fatty acid produced by R. glutinis in all media was oleic acid, whose fraction reached 63.94 ± 0.58%. Total carotenoid yield was significantly increased with low initial pH, high temperature, illumination, certain amounts of urea, glycerol and cultivation time. Up to 192.09 ± 0.16μg/g cell carotenoid yield was achieved. Torularhodin could be selectively produced at high pH, low temperature and with urea and glycerol supplementation. To selectively induce torulene synthesis, cultivation conditions should have low pH, high temperature and illumination. In addition, low pH, high temperature and urea supplementation served high production of β-carotene. Up to 85.40 ± 0.76, 80.67 ± 1.40 and 39.45 ± 0.69% of torulene, torularhodin and β-carotene, respectively, were obtained under selected conditions. KEY POINTS: • Cultivation conditions selectively induced target carotenoids and lipids • 41.40 ± 0.21% (w/w) lipid content and 192.09 ± 0.16μg/g cell carotenoid yield were achieved • Markedly high selectivity values for torularhodin and torulene were achieved.

Overexpression of the KAS Ⅲ-like gene YxwZ3 increases carotenoids production in Aurantiochytrium sp. SZU445

Identifying gene that enhances specific product accumulation of industrial strains is a central tenet of metabolic engineering. Aurantiochytrium sp. has come into the limelight by virtue of their biotechnological importance in the production of bioactive compounds, including fatty acids and carotenoids. However, there is restrict in the high yield of carotenoids in Aurantiochytrium sp. This study, a KAS Ⅲ-like enzyme ‘YxwZ3′ were successfully used to construct recombinant cassette. We utilized TEF1 and EM7 promoters to overexpress KAS Ⅲ-like enzyme YxwZ3 in Aurantiochytrium sp. SZU445. The transformed strain displayed a 4.88-fold increase in the yield of total carotenoids compared to the wild-type strain, involved in β-carotene (37.96 μg/g), phytoene (1.55 μg/g), β-cryptoxanthin (1.57 μg/g), antheraxanthin (0.02 μg/g), α-cryptoxanthin (0.25 μg/g) and echinenone (0.72 μg/g) with the accumulation of fatty acids downregulated. It is speculated that more malonyl-CoA was used in the MVA pathway for carotenoids synthesis based on overexpression of YxwZ3 strains instead of the fatty acid synthesis pathway. In addition, the content of total carotenoids of YxwZ3 overexpression lines was increased 1.33 times (56.52 μg/g) through optimization of fermentation condition based on response surface methodology. These findings demonstrated a significant impact of KAS Ⅲ-like enzyme YxwZ3 on carotenoids in Aurantiochytrium sp., and provided the theoretical basis for constructing the high-yielding carotenoid-producing strains.

Green extraction of bioactive components from carrot industry waste and evaluation of spent residue as an energy source

Carrot processing industries produce 25–30% of waste in the form of carrot rejects, peels, and pomace which contain a large amount of high-value bioactive components. Green extraction of the bioactive components from carrot rejects with green solvents using closed-vessel energy-intensive microwave-assisted extraction was the objective of this work. In this work, three experimental studies were implemented. One uses 8 different green solvents for maximum yield of bioactive using green technology, and the other for the optimization of Microwave-assisted Extraction (MAE) parameters to enhance the bioactive components yield. Response Surface Methodology was employed to optimize the processing parameters including temperature, time, solid to solvent ratio, and solvent type. The optimized extraction conditions: treatment temperature of 50 °C for 5 min gave a significantly higher yield of total carotenoids (192.81 ± 0.32 mg carotenoids/100 g DW), total phenolic (78.12 ± 0.35 g GAE/100 g DW), and antioxidants by FRAP (5889.63 ± 0.47 mM TE/100 g DW), ABTS (1143.65 ± 0.81 mM TE/100 g DW), and DPPH (823.14 ± 0.54 mM TE/100 g DW) using a solvent combination of hexane and ethanol (1:3) with solid to solvent ratio of 1:40 (w/v). This green technology in combination with GRAS solvents promoted the best recovery of bioactive from carrot rejects. Moreover, the solid residue remained after the extraction of bioactive components exhibited higher carbon content (46.5%) and calorific value (16.32 MJ/kg), showcasing its potential to be used as an energy source.

Optimization of Culture Conditions for Total Carotenoid Amount Using Response Surface Methodology in Green Microalgae / Ankistrodesmus convolutus

Commercial carotenoids of green microalgae have become significant especially for their applications in the cosmetic, pharmaceutical, food and feed industries. Effects of physical and chemical parameters on carotenoid contents in isolated microalgal species have been investigated. The variables of shaking rate, nitrogen concentration and light intensity affect biomass production and the synthesis of carotenoids in the green microalgae were investigated using the statistical design by Box-Behnken (BBD) employing Response Surface Methodology (RSM). Furthermore, the optimized cultivation conditions using BBD for Chlorella vulgaris, Ankistrodesmus convolutus, Dunaliella salina, Tetraselmis striata were determined using the spectrophotometric method to enhance carotenoid concentration. A. convolutus within the green algae was detected with the highest carotenoid concentration. The optimum conditions results indicated that the growth of A. convolutus (0.55 mg/L) and production of total carotenoids (25.1138 mg/g biomass) were found at the stirrer rate of 100 rpm under the light intensity of 100 μE/m2 s, and in the nutrient component of 8.82 mM NaNO3 . These conditions were validated experimentally for total carotenoid yield (24.13 mg/g biomass). After that the production was performed in a flat-plate photobioreactor with a volume of 6L based on the optimized conditions and the carotenoid profile was defined by HPLC-DAD using standards such as violaxanthin, astaxanthin and β-carotene. This study proposes that the RSM approach can be used to define optimal conditions for large-scale production of carotenoids by A. convolutus. 

Development of a microwave‐assisted solvent extraction process for the extraction of high‐value carotenoids from Chlorella biomass

AbstractThe commercial production of carotenoids as bioactive commodities from microalgae has been severely limited due to the nature of the microalgal outer cell matrix. Microwave technology offers a rapid method for obtaining larger amounts of these biochemical compounds. The process facilitates cell‐wall rupture, releasing the inner cell components. Chlorella biomass, raised in an outdoor raceway pond, is used for downstream extraction of carotenoids by following the microwave‐assisted solvent extraction (MAE) approach. The response surface modeling (RSM) strategy was employed to optimize the two independent parameters, power and extraction time, with a two‐level central composite design (CCD). Acetone, hexane, methanol, hexane : acetone (1:1), hexane : ethanol (7:3) were used as solvents of choice. Acetone gave a total carotenoid yield of 0.061 ± 0.003 mg gm−1 under optimum microwave power and time; 130 W and 1.69 min. The optimized yield from hexane was 0.00173 ± 0.005 mg gm−1 with an exposure time of 1 min to 100 W. The total carotenoid yield of the methanol‐based extraction batch was 0.0371 ± 0.004 mg gm−1 with 157 W and 1 min of extraction time. The solvent mixtures of hexane : acetone gave 0.0398 ± 0.002 mg gm−1 (185 W for 1.7 min) and hexane : ethanol gave 0.0383 ± 0.004 mg gm−1 (195 W, 1.6 min), respectively. The results indicate a satisfactory outcome to the process. They also show microwave‐based extraction to be a fast, economic, reproducible, and repeatable method in comparison with the conventional strategies used for recovering the sensitive natural pigments. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

A critical look into different salt removal treatments for the production of high value pigments and fatty acids from marine microalgae Chlorella vulgaris (NIOT-74)

The prime challenge in seawater culture of microalgae for high value biomolecules production is presence of salt. Hence, twelve different salt removal treatments were evaluated for their impact on the lutein, total carotenoid, chlorophyll yields and fatty acid profile of marine microalgae Chlorella vulgaris (NIOT-74). The effectiveness of different treatments on salt removal was also visualized with the aid of Scanning Electron Microscope (SEM). Among the tested treatments, washing the algal biomass with 0.5 % HCl augmented the lutein (11.56 mg/g) and total carotenoid yield (60.88 mg/g) 1.82 and 1.86 fold respectively, in comparison to untreated control. Highest chlorophyll content (30.64 mg/g) was noticed in the distilled water wash treatment. Different salt removal treatments also impacted the fatty acid profile and degree of unsaturation of the fatty acids significantly. This study thus, signified the importance of salt removal treatments for the commercial production of biomolecules from marine microalgae cultured in natural seawater.

Carotenoid Production by Rhodosporidium paludigenum Using Orange Peel Extract as Substrate

Carotenoids are fat-soluble pigments that have various benefits in health and beauty. The demand and market of carotenoids are increasing; thus, the faster and cheaper biological production of these pigments using microorganisms is desired. In this study, the optimum medium pH and nitrogen concentration for carotenoid production by Rhodosporidium ( R. ) paludigenum using orange peel extract as substrate were determined. The soluble sugars from orange peels were extracted using distilled water at 100 °C. The yeast inoculum was cultivated in Yeast Peptone Dextrose (YPD) media before fermentation. The independent variables in the fermentation factorial design included initial medium pH (5; 6; and 7) and nitrogen concentration (0; 1; and 1.75 g/L urea in the medium). The decrease in reducing sugar concentration and the increase in biomass dry weight during fermentation demonstrated carbon source consumption by R. paludigenum for growth and carotenoid production. On the sixth day of fermentation (D6), the culture was harvested for the total carotenoid extraction and determination. The highest total carotenoid yield (107.63 µg/g) was achieved by the treatment group with an initial medium pH of 6 without nitrogen supplementation. This result indicated the orange peel extract potential as a substrate for carotenoid production using R. paludigenum as a workhorse. This was the first reported research in natural carotenoid generation using R. paludigenum (strain InaCC Y-236) locally isolated in Indonesia as the producer and orange peel extract as the substrate. Thus, this research would enrich the microbial carotenoid exploration and waste valorization to value-added products at the same time. The study can then be developed further and upscaled for industrial applications.Â

Carotenoids production in wild yeasts isolated from aquatic systems in Cali, Colombia

Introducción: Los carotenoides son fuente importante de actividades biológicas funcionales, tales como antioxidantes o antimicrobianas, además de tener gran impacto a nivel industrial, ya sea en cosmética o suplementación animal en acuacultura. Se han reportado varias moléculas novedosas a partir de aislamientos en Latinoamérica, principalmente en la Patagonia, Argentina. Sin embargo, no hay reportes en Colombia que evalúen la producción de carotenoides en levaduras nativas pigmentadas. Objetivo: Se evaluó la capacidad de producción de carotenoides en levaduras nativas aisladas de lagos, ríos y aguas residuales de la ciudad de Cali, Colombia. Materiales y métodos: Se caracterizaron 30 levaduras provenientes de dos colecciones. De estas se obtuvo su biomasa, rendimiento de carotenoides totales y producción de β-caroteno. Las cepas promisorias fueron identificadas secuenciando la región ITS1-5.8S-ITS2. Resultados: El mayor rendimiento en la extracción de pigmentos se obtuvo para las cepas P11A (84,36 ± 5,24 µg/g) y Rhodotorula paludigena CS13 (56,26 ± 7,08 µg/g), mientras que las concentraciones más altas de β-caroteno fueron 10,2 µg/mL (R. paludigena CS13) y 9,7 µg/mL (R. mucilaginosa/alborubescens P10A). La cinética de crecimiento y producción de pigmentos durante cinco días fue óptima para la cepa P11A, ya que hubo un aumento en el rendimiento de carotenoides totales 10 veces mayor (48 h: 109,62 µg/g, 120 h: 1403,10 µg/g). Conclusiones: En este estudio se encontró que levaduras aisladas de sistemas acuáticos son promisorias para la producción de pigmentos carotenoides (incluyendo β-caroteno), siendo su extracción y caracterización viable para futuros estudios biotecnológicos.

Efficiency of ultrasound assisted extract of <em>Delonix regia</em> petals as natural antioxidant on the oxidative stability of sunflower oil

The possibility of improving the oxidative stability of sunflower oil by enriching it with carotenoids from Delonix regia petals was studied. A combination of ultrasound-assisted extraction and stirring techniques was used. The optimal conditions were material/solvent ratio of 1:20 (w/v), ultrasonic power of 30 W and extraction time of 50 min. Under these conditions, the yield of total carotenoids was 503.0 μg/g dry weight. Increasing the acoustic power density degraded carotenoids. A HPLC analysis was used for the quantification of β-carotene in the extract. The DPPH radical scavenging activity and ferric reducing antioxidant power of the carotenoid-rich extract were found to be superior to the standard Butylated hydroxyl toluene (BHT). The enrichment of sunflower oil with carotenoid-rich extract at 67.46 mg carotenoids/kg oil improved its oxidative stability by more than 50% as measured by the Rancimat method. These results suggest that the investigated extract has the potential to be used as a bio-preservative in food products.

Drying Optimisation to Obtain Carotenoid-Enriched Extracts from Industrial Peach Processing Waste (Pomace)

In this study, peach pomace (PP) moisture reduction using conventional oven-drying was investigated by implementing the Box-Behnken experimental design, considering two major process variables, time—t and temperature—T. The purpose was the optimisation of the process to obtain PP extracts as rich as possible in total carotenoids (TCn). It was shown that effective moisture removal up to a final level of approximately 24%, could be achieved after 8.27 h (496 min) at 70 °C. Under these optimised drying conditions, the maximum carotenoid yield was 84.57 ± 8.56 μg CtE g−1 dm. This yield was by almost 63% lower than that achieved using fresh (non-dried) samples. Temperatures higher than 70 °C were demonstrated to be even more detrimental in this regard, yet from the model built, it was made clear that prolonged drying time may bring about a more pronounced negative effect on the total carotenoid yield. The drop in total carotenoid content of PP as a result of drying was accompanied by a significant decline in the antiradical activity of PP extracts.

Isolation of a Stable Astaxanthin-Hyperproducing Mutant of Xanthophyllomyces dendrorhous Through Random Mutagenesis

Astaxanthin is a red xanthophyll pigment which is widely commercially used due to its strong antioxidant properties. The heterobasidiomycetous yeast, Xanthophyllomyces dendrorhous, is one of the main microorganisms for industrial production of astaxanthin. However, astaxanthin content is low in wild type yeast strain. In our study, we had successfully isolated X. dendrorhous mutant with higher astaxanthin production capacity using chemical mutagen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), through β-ionone screening. The astaxanthin-hyperproducing mutant X. dendrorhous M34 had total carotenoid yield of 602.4 µg/g DW and a 110.8% increment of total carotenoid content compared to wild type. Survival studies indicated that MNNG treatment of yeast led to higher lethality in recipient cells compared to ethyl methanesulfonate (EMS) one. EMS-mutated strains did not show promising carotenoid yield during the screening process by β-ionone and the rate of reverse mutation was very high. In the stability test, no reversion was observed in X. dendrorhous M34 mutant after 10 successive transfers in culture broth. Reversed-phase HPLC showed that the elution profiles of carotenoid extracts of M34 and wild type X. dendrorhous were in agreement with the authentic standard and the major peak in M34 extract was identified as astaxanthin. The stable mutant with high yield of astaxanthin obtained in this work could be a suitable candidate for the industrial-scale production of astaxanthin.

Rapid Production of Natural Carotenoids from <em>Rhodobacter sphaeroides</em>

Rhodobacter sphaeroides is abundant in natural carotenoids. However, fermentation under light growth conditions for carotenoids biosynthesis is time consuming. In the present study, fermentation for 36 h under micro-aerobic growth conditions was employed to rapidly produce carotenoids from Rb. Sphaeroides . Orthogonal experiments suggested that the optimal fermentation process was: temperature 33°C, inoculation amount 8%, fermentation duration 36 h. The yield of total carotenoids was 11.542 mg/L. Real-time PCR indicated that expression levels for crtA , crtD , crtE and crtI at the time fermentation for 36 h were higher than that of fermentation for 48 h. TLC analysis showed that at least 6 well separated bands were observed. Temperature, pH and light tolerance tests indicated that the total carotenoids were stable. 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) assay suggested that the total carotenoids exhibited high anti-oxidant activity and the IC50 value of DPPH radical scavenging test was about 8.175 μg/mL. The present study will promote to produce natural carotenoids from microorganism in large-scale.

Rapid and environmentally-friendly extraction of carotenoids from Blakeslea trispora.

A rapid and environmentally-friendly method of carotenoid extraction from Blakeslea trispora was performed using low-pressure steam explosion for cell disruption and ethyl lactate for the extraction. Response surface methodology determined the optimal extraction conditions to obtain the maximum carotenoid yield. These optimal conditions consisted of low-pressure steam explosion at 0.2MPa for 4.4min, followed by extraction with ethyl lactate at a ratio of 1:25 at 39°C for 45min. Optimal technology was used, and the total carotenoid yield reached 95.6%. In contrast to previously methods, the time-consuming drying process was eliminated and the extraction time was significantly decreased. Ethyl lactate is an environmentally-friendly solvent with low toxicity in this method.

Response surface methodology toward the optimization of high-energy carotenoid extraction from Aristeus antennatus shrimp

High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE.Response surface methodology (RSM) is used for the optimization of extraction methodologies, also being applied to optimize high energy techniques. Three independent variables, namely extraction time, ultrasound or microwave power and solvent/material ratio, were investigated for both methods by employing a 16-run three-level Box–Behnken design (BBD). Considering the extraction efficiency for carotenoids from Aristeus antennatus shrimp, the selected conditions for UAE were 5min, 600W and 10:1mLg−1. Acetone was the solvent of choice for the extraction procedure. For MAE, the best experimental values were 7min, 30W and 20:1mLg−1 using n-hexane:acetone:ethanol 2:1:1 (v/v/v) as extraction solvent. The determination of total carotenoid yield was carried out using the spectophotometric calibration curve (A=0.1646(±0.0061)C−0.005(±0.022), R2=0.996, n=3) of a standard mix solution of canthaxanthin, zeaxanthin and lutein at 452.1nm. Under the selected conditions, the yield of total carotenoids for UAE was 23.4(±2.3) and 6.73(±0.56)mg of carotenoids per 100g dry sample for the head and the body of shrimp, while for MAE was 23.92(±0.63) and 13.3(±1.1)mg of carotenoids per 100g dry sample, respectively. The recovery of both methods was calculated between 60 and 105%. The results indicate that high-energy extraction techniques are faster, less laborious, more repeatable and reproducible methods than the conventional approaches for the quantitative recovery of sensitive bioactive compounds. Moreover, the recovery of a high-added value group of bioactive molecules from natural sources, such as carotenoids, can constitute a profitable and valuable commercial alternative, as these compounds can be used as dietary supplements, food color enhancers and additives in animal feeds, functional foods, preservatives, pharmaceuticals and cosmetics.

Progress toward an Escherichia coli canthaxanthin bioprocess

Canthaxanthin has significant commercial value due to its use as an antioxidant and feed additive in aquaculture and poultry farms. The biological production of high-value carotenoids, such as canthaxanthin, represents a significant challenge. Presented here is an Escherichia coli bioprocess, which includes the recombinant production of a strain, a novel medium and a fermentation process, for the efficient biosynthesis of canthaxanthin. The chromosomal overexpression of the E. coli genes Idi, Dxs and Dxr increased the carbon flux into the plasmid-based canthaxanthin biosynthetic pathway, achieving a total carotenoid productivity of 11.7mg/g (91% canthaxanthin). The development of a novel culture medium increased the productivity 2.9-fold to 78.2mg/L total carotenoids. This high-titer platform was subsequently employed for the analysis of mutations known to be advantageous to carotenoid biosynthesis, providing the first such evaluation in a high titer background. This demonstrated that thee increased expression of IspB or the deletion of PykF, PykA or YtjC improved the total carotenoid yield, whereas the increased expression of Pps and Ppc, was not improve productivity. This analysis resulted in an increase in the carotenoid yield to 16.1mg/g. The use of 1L lab-scale fermentations allowed for further improvements in productivity, and 170mg/L total carotenoids was obtained.

Supercritical Carbon Dioxide Extraction of Carotenoids from Marigold Flower Using Orthogonal Test Design

Supercritical carbon dioxide extraction had been used in the extraction conditions for carotenoids from the marigold flower (Tagetes erecta L.). Five significant factors (particle size, temperature, pressure, time and co-solvent addition) on total carotenoid yield were obtained using one-at-a-time design (p≤0.05). The optimal extraction conditions were 55 oC, 50 MPa and 180 min. Under these conditions, the yield of carotenoids was 6.872mg/g.

Separation of Carotenoids from Physalis Alkekengi var. Francheti through Supercritical CO2

Separation of carotenoids has been carried out on the calyx of Physalis alkekengi var. francheti by means of supercritical CO2. The influences of various parameters such as extraction pressure, temperature, processing time and particle size on the total carotenoid yield extracted are investigated in detail. A diffusion layer theory model is used to correlate the extraction yield vs. time profiles and it performs rather satisfactorily to describe the extraction process with an average absolute relative deviation varying from 3.2 to 11.0%.

Characterization of cyanobacterial β‐carotene ketolase and hydroxylase genes in Escherichia coli, and their application for astaxanthin biosynthesis

Carotenoid biosynthesis is highly conserved and well characterized up to the synthesis of beta-carotene. Conversely, the synthesis of astaxanthin from beta-carotene is less well characterized. Regardless, astaxanthin is a highly sought natural product, due to its various industrial applications and elevated antioxidant capacity. In this article, 12 beta-carotene ketolase and 4 beta-carotene hydroxylase genes, isolated from 5 cyanobacterial species, are investigated for their function, and potential for microbial astaxanthin synthesis. Further, this in vivo comparison identifies and applies the most promising genetic elements within a dual expression vector, which is maintained in Escherichia coli. Here, combined overexpression of individual beta-carotene ketolase and beta-carotene hydroxylase genes, within a beta-carotene accumulating host, enables a 23.5-fold improvement in total carotenoid yield (1.99 mg g(-1)), over the parental strain, with >90% astaxanthin.

Supercritical fluid extraction of carotenoids and chlorophyll a from Synechococcus sp.

Supercritical carbon dioxide extraction of carotenoids and chlorophylls is an alternative to solvent extraction because it provides a high-speed extraction process with a simple purification stage. In the study described here, carotenoid and chlorophyll extraction with supercritical CO 2 was explored using dry biomass from a marine cyanobacterium Synechococcus sp. as the raw material. The operation conditions were as follows: pressures of 100, 200, 300, 400 and 500 bar, temperatures of 40 , 50 and 60 °C. Analysis of the extracts was performed by measuring the absorbance and by using an empirical correlation. The results demonstrate that the highest extraction yield of total carotenoids is obtained operating at a pressure of 300 bar and a temperature of 50 °C. The most appropriate operating conditions to obtain the best yield in the extraction of chlorophyll a are 500 bar and 60 °C. The highest carotenoids/chlorophylls (Carot/Chlor) ratio is obtained at 200 bar and 60 °C. Under these operating conditions a higher selectivity is obtained and this should facilitate the separation and purification of the two extracted pigments.