Assessment of carotenoid production by Dunaliella salina in different culture systems and operation regimes

Nannochloropsis oceanica as a Source of Bioactive Compounds: Mapping the Effects of Cultivation Conditions on Biomass Productivity and Composition Using Response Surface Methodology

Microalga Nannochloropsis oceanica presents a promising source of high-value food ingredients such as protein, omega-3 fatty acids, and vitamins. To fully unlock its potential, a thorough understanding of how cultivation conditions affect both growth and the nutritional composition is required. Hence, this study aimed to test and model the effects of temperature, light intensity, and salinity on biomass productivity and the final contents of protein, eicosapentaenoic acid (EPA), and vitamin K2 using response surface methodology (RSM). The RSM experiment revealed that the highest temperature and light intensity tested favored biomass productivity and protein content. According to the generated models, the two responses peaked with 0.135 g DM·L-1·day-1 and 0.559 g·g-1 DM, respectively, at 27 °C and 300-350 µmol·m-2·s-1. In contrast, the contents of both EPA and menaquinone-4 (MK-4), the only detected K vitamer, were stimulated at the lowest tested temperature. Based on the generated models, the two responses peaked with 0.037 g·g-1 DM and 89.3 µg·g-1 DM, respectively, at 19 °C combined with 3.0% salinity (EPA) or 120 µmol·m-2·s-1 (MK-4). Although additional optima may exist beyond the tested conditions, these findings provide valuable information on N. oceanica's cellular response to changes in key cultivation conditions. Furthermore, it shows that two-stage cultivation may be needed to fully unlock the potential of this microalga as a future source of valuable lipid ingredients.

Exploring Extremotolerant and Extremophilic Microalgae: New Frontiers in Sustainable Biotechnological Applications

Exploring extremotolerant and extremophilic microalgae opens new frontiers in sustainable biotechnological applications. These microorganisms thrive in extreme environments and exhibit specialized metabolic pathways, making them valuable for various industries. The study focuses on the ecological adaptation and biotechnological potential of these microalgae, highlighting their ability to produce bioactive compounds under stress conditions. The literature reveals that extremophilic microalgae can significantly enhance biomass production, reduce contamination risks in large-scale systems, and produce valuable biomolecules such as carotenoids, lipids, and proteins. These insights suggest that extremophilic microalgae have promising applications in food, pharmaceutical, cosmetic, and biofuel industries, offering sustainable and efficient alternatives to traditional resources. The review concludes that further exploration and utilization of these unique microorganisms can lead to innovative and environmentally friendly solutions in biotechnology.

Arts, cultural heritage, sciences, and micro-/bio-/technology: Impact of biomaterials and biocolorants from antiquity till today!

Nature has inspired and provided humans with ideas, concepts, and thoughts on design, art, and performance for millennia. From early societies when humankind often took shelter in caves, until today, many materials and colorants to express feelings or communicate with one another were derived from plants, animals, or microbes. In this manuscript, an overview of these natural products used in the creation of art is given, from paintings on rocks to fashionable dresses made from bacterial cellulose. Besides offering many examples of art works, the origin and application of various biomaterials and colorants are discussed. While many facets of our daily lives have changed over millennia, one certainty has been that humans have an intrinsic need to conceptualize and create to express themselves. Driven by technological advances in the past decades and in the light of global warming, new and often more sustainable materials and colorants have been discovered and implemented. The impact of art on human societies remains relevant and powerful.

ONE-SENTENCE SUMMARY

This manuscript discusses the use of biomaterials and biocolorants in art from a historical perspective, spanning 37,000 bc until today.

Microalgae, Seaweeds and Aquatic Bacteria, Archaea, and Yeasts: Sources of Carotenoids with Potential Antioxidant and Anti-Inflammatory Health-Promoting Actions in the Sustainability Era

Carotenoids are a large group of health-promoting compounds used in many industrial sectors, such as foods, feeds, pharmaceuticals, cosmetics, nutraceuticals, and colorants. Considering the global population growth and environmental challenges, it is essential to find new sustainable sources of carotenoids beyond those obtained from agriculture. This review focuses on the potential use of marine archaea, bacteria, algae, and yeast as biological factories of carotenoids. A wide variety of carotenoids, including novel ones, were identified in these organisms. The role of carotenoids in marine organisms and their potential health-promoting actions have also been discussed. Marine organisms have a great capacity to synthesize a wide variety of carotenoids, which can be obtained in a renewable manner without depleting natural resources. Thus, it is concluded that they represent a key sustainable source of carotenoids that could help Europe achieve its Green Deal and Recovery Plan. Additionally, the lack of standards, clinical studies, and toxicity analysis reduces the use of marine organisms as sources of traditional and novel carotenoids. Therefore, further research on the processing of marine organisms, the biosynthetic pathways, extraction procedures, and examination of their content is needed to increase carotenoid productivity, document their safety, and decrease costs for their industrial implementation.

Microalgal Carotenoids: Therapeutic Application and Latest Approaches to Enhance the Production

Microalgae are microscopic photosynthetic organisms frequently found in fresh and marine water ecosystems. Various microalgal species have been considered a reservoir of diverse health-value products, including vitamins, proteins, lipids, and polysaccharides, and are broadly utilized as food and for the treatment of human ailments such as cancer, cardiovascular diseases, allergies, and immunodeficiency. Microalgae-derived carotenoids are the type of accessory pigment that possess light-absorbing potential and play a significant role in metabolic functions. To date, nearly a thousand carotenoids have been reported, but a very less number of microalgae have been used for the commercial production of carotenoids. This review article briefly discussed the carotenoids of microalgal origin and their therapeutic application. In addition, we have briefly compiled the optimization of culture parameters used to enhance microalgal carotenoid production. In addition, the latest biotechnological approaches used to improve the yields of carotenoid has also been discussed.

Recent Advances in Marine Microalgae Production: Highlighting Human Health Products from Microalgae in View of the Coronavirus Pandemic (COVID-19)

Blue biotechnology can greatly help solve some of the most serious social problems due to its wide biodiversity, which includes marine environments. Microalgae are important resources for human needs as an alternative to terrestrial plants because of their rich biodiversity, rapid growth, and product contributions in many fields. The production scheme for microalgae biomass mainly consists of two processes: (I) the Build-Up process and (II) the Pull-Down process. The Build-Up process consists of (1) the super strain concept and (2) cultivation aspects. The Pull-Down process includes (1) harvesting and (2) drying algal biomass. In some cases, such as the manufacture of algal products, the (3) extraction of bioactive compounds is included. Microalgae have a wide range of commercial applications, such as in aquaculture, biofertilizer, bioenergy, pharmaceuticals, and functional foods, which have several industrial and academic applications around the world. The efficiency and success of biomedical products derived from microalgal biomass or its metabolites mainly depend on the technologies used in the cultivation, harvesting, drying, and extraction of microalgae bioactive molecules. The current review focuses on recent advanced technologies that enhance microalgae biomass within microalgae production schemes. Moreover, the current work highlights marine drugs and human health products derived from microalgae that can improve human immunity and reduce viral activities, especially COVID-19.

Circular biomanufacturing through harvesting solar energy and CO2

Using synthetic biology, it is now time to expand the biosynthetic repertoire of plants and microalgae by utilizing the chloroplast to augment the production of desired high-value compounds and of oil-, carbohydrate-, or protein-enriched biomass based on direct harvesting of solar energy and the consumption of CO₂. Multistream product lines based on separate commercialization of the isolated high-value compounds and of the improved bulk products increase the economic potential of the light-driven production system and accelerate commercial scale up. Here we outline the scientific basis for the establishment of such green circular biomanufacturing systems and highlight recent results that make this a realistic option based on cross-disciplinary basic and applied research to advance long-term solutions.

Reuse of sea water reverse osmosis brine to produce Dunaliella salina based β-carotene as a valuable bioproduct: A circular bioeconomy perspective

Due to population growth and global warming, the use of the sea water reverse osmosis process to obtain freshwater is increasing rapidly. A sustainable method with low environmental impact is limited for the management of brine with a high salt content, which is released as a result of the process. Some microalgae species can grow in salty environments and produce β-carotene. This study aims to evaluate the commercial potential of β-carotene production from microalgae grown in sea water reverse osmosis brine from a bioeconomy perspective. Synthetic media are often used for the production of β-carotene from algae, the use of sea water reverse osmosis brine is not common and the commercial potential of this application has not been evaluated before. In terms of the development of the β-carotene market, the strengths and weaknesses of the process, opportunities, and threats are thoroughly examined in this report. Also, with the use of sea water reverse osmosis, a daily 750 tons of algal β-carotene can be produced. The biotechnological production of microalgal β-carotene and the reuse of salt water within the scope of circular bioeconomy are seen as a sustainable solution due to the fact that the strengths of the process are dominant, and the market value of natural β-carotene is increasing day by day.

Potential of a mixed culture of microalgae for accumulation of beta-carotene under different stress conditions

Beta-carotene, a pigment found in plants, is mainly produced by microalgae. Nevertheless, this production has only been investigated in pure cultures. Beta-carotene production through mixed culture eliminates the costly procedure of sterilization and contamination prevention needed for pure cultures. In this study, for the first time, the growth, beta-carotene, and chlorophyll production of a mixed culture of microalgae from Caspian Sea was investiagted under different stress conditions. At the condition of tripled light intensity and nitrogen starvation, beta-carotene content increased from 18.03 to 43.8 and 46.5 mol beta-carotene g−1 protein, respectively. However, the salinity of 4 mol L−1 caused the beta-carotene content to fall to zero. The blank sample reached a constant value of 23 mol beta-carotene g−1protein. The comparable results with the specific monoculture species exhibit the high potential of a mixed culture of microalgae for beta-carotene production without need of the high sterilization cost. Nevertheless, more research is needed for where it can be a good substitute for pure culture.

Microalgal-based feed: promising alternative feedstocks for livestock and poultry production

There is an immediate need to identify alternative sources of high-nutrient feedstocks for domestic livestock production and poultry, not only to support growing food demands but also to produce microalgae-source functional foods with multiple health benefits. Various species of microalgae and cyanobacteria are used to supplement existing feedstocks. In this review, microalgae have been defined as a potential feedstock for domestic animals due to their abundance of proteins, carbohydrates, lipids, minerals, vitamins, and other high-value products. Additionally, the positive physiological effects on products of animals fed with microalgal biomass have been compiled and recommendations are listed to enhance the assimilation of biomolecules in ruminant and nonruminant animals, which possess differing digestive systems. Furthermore, the role of microalgae as prebiotics is also discussed. With regards to large scale cultivation of microalgae for use as feed, many economic trade-offs must be considered such as the selection of strains with desired nutritional properties, cultivation systems, and steps for downstream processing. These factors are highlighted with further investigations needed to reduce the overall costs of cultivation. Finally, this review outlines the pros and cons of utilizing microalgae as a supplementary feedstock for poultry and cattle, existing cultivation strategies, and the economics of large-scale microalgal production.

Unlocking the Health Potential of Microalgae as Sustainable Sources of Bioactive Compounds

Microalgae are known to produce a plethora of compounds derived from the primary and secondary metabolism. Different studies have shown that these compounds may have allelopathic, antimicrobial, and antipredator activities. In addition, in vitro and in vivo screenings have shown that several compounds have interesting bioactivities (such as antioxidant, anti-inflammatory, anticancer, and antimicrobial) for the possible prevention and treatment of human pathologies. Additionally, the enzymatic pathways responsible for the synthesis of these compounds, and the targets and mechanisms of their action have also been investigated for a few species. However, further research is necessary for their full exploitation and possible pharmaceutical and other industrial applications. Here, we review the current knowledge on the chemical characteristics, biological activities, mechanism of action, and the enzymes involved in the synthesis of microalgal metabolites with potential benefits for human health.

A simple and fast experimental protocol for the extraction of xanthophylls from microalga Chlorella luteoviridis

This study aimed to optimize the key parameters of extraction methods and to increase the recovery yields of intact xanthophylls (violaxanthin, zeaxanthin, astaxanthin) from microalgae (Chlorella luteoviridis). An effective, simple, and fast extraction protocol is described. It consists of a grinding pretreatment followed by a microwave-assisted extraction, using ethanol 90% as an environmentally preferable extraction solvent. Xanthopylls were quantified using high performance liquid chromatography. Irradiation time of 6 s only resulted in the extraction of violaxanthin (4.479 ± 0.009 mg/g), astaxanthin (4.154 ± 0.013 mg/g), and zeaxanthin (4.776 ± 0.120 mg/g). The described protocol seems to be the fastest extraction method of xantophylls compared to the literature and could be an advantage for industrial scale, while saving time and energy.

Microalgal Enzymes with Biotechnological Applications

Enzymes are essential components of biological reactions and play important roles in the scaling and optimization of many industrial processes. Due to the growing commercial demand for new and more efficient enzymes to help further optimize these processes, many studies are now focusing their attention on more renewable and environmentally sustainable sources for the production of these enzymes. Microalgae are very promising from this perspective since they can be cultivated in photobioreactors, allowing the production of high biomass levels in a cost-efficient manner. This is reflected in the increased number of publications in this area, especially in the use of microalgae as a source of novel enzymes. In particular, various microalgal enzymes with different industrial applications (e.g., lipids and biofuel production, healthcare, and bioremediation) have been studied to date, and the modification of enzymatic sequences involved in lipid and carotenoid production has resulted in promising results. However, the entire biosynthetic pathways/systems leading to synthesis of potentially important bioactive compounds have in many cases yet to be fully characterized (e.g., for the synthesis of polyketides). Nonetheless, with recent advances in microalgal genomics and transcriptomic approaches, it is becoming easier to identify sequences encoding targeted enzymes, increasing the likelihood of the identification, heterologous expression, and characterization of these enzymes of interest. This review provides an overview of the state of the art in marine and freshwater microalgal enzymes with potential biotechnological applications and provides future perspectives for this field.

Flocculation-flotation harvesting mechanism of Dunaliella salina: From nanoscale interpretation to industrial optimization

Dunaliella salina is a green microalgae species industrially exploited for its capacity to produce important amounts of carotenoid pigments. However in low nitrogen conditions in which they produce these pigments, their concentration is low, which results in harvesting difficulties and high costs. In this work, we propose a new solution to efficiently harvest D. salina at the pre-industrial scale, using flocculation/flotation harvesting induced by NaOH addition in the medium. We first show, using numerical simulations and nanoscale atomic force spectroscopy experiments, that sweeping mechanism in formed magnesium hydroxide precipitate is only responsible for D. salina flocculation in hypersaline culture medium upon NaOH addition. Based on this understanding of the flocculation mechanism, we then evaluate the influence of several parameters related to NaOH mixing and magnesium hydroxide precipitation and show that NaOH concentration, mixing, and salinity of the medium can be optimized to achieve high flocculation/flotation harvesting efficiencies in laboratory-scale experiments. We finally successfully scale-up the data obtained at lab-scale to a continuous pre-industrial flotation pilot, and achieve up to 80% of cell recovery. This interdisciplinary study thus provides original results, from the nano to the pre-industrial scale, which allow the successful development of an efficient large-scale D. salina harvesting process. We thus anticipate our results to be the starting point for further optimization and industrial use of this flocculation/flotation harvesting technique.

Potential of Microalgae Carotenoids for Industrial Application

Microalgae cultivation, when compared to the growth of higher plants, presents many advantages such as faster growth, higher biomass productivity, and smaller land area requirement for cultivation. For this reason, microalgae are an alternative platform for carotenoid production when compared to the traditional sources. Currently, commercial microalgae production is not well developed but, fortunately, there are several studies aiming to make the large-scale production feasible by, for example, employing different cultivation systems. This review focuses on the main carotenoids from microalgae, comparing them to the traditional sources, as well as a critical analysis about different microalgae cultivation regimes that are currently available and applicable for carotenoid accumulation. Throughout this review paper, we present relevant information about the main commercial microalgae carotenoid producers; the comparison between carotenoid content from food, vegetables, fruits, and microalgae; and the great importance and impact of these molecule applications, such as in food (nutraceuticals and functional foods), cosmetics and pharmaceutical industries, feed (colorants and additives), and healthcare area. Lastly, the different operating systems applied to these photosynthetic cultivations are critically discussed, and conclusions and perspectives are made concerning the best operating system for acquiring high cell densities and, consequently, high carotenoid accumulation.

The potential of microalgae biorefineries in Belgium and India: An environmental techno-economic assessment

This study performs an environmental techno-economic assessment (ETEA) for multiple microalgae biorefinery concepts at different locations, those being Belgium and India. The ETEA methodology, which integrates aspects of the TEA and LCA methodologies and provides a clear framework for an integrated assessment model, has been proposed and discussed. The scenario in India has a higher profitability with a NPV of €40 million over a period of 10 years, while the environmental impact in Belgium is lower. The inclusion of a medium recycling step provides the best scenario from both perspectives. The crucial parameters for feasibility are the β-carotene price and content, the upstream environmental impact of electricity and the maximum biomass concentration during cultivation. The identification of these parameters by the ETEA guides future technology developments and shortens the time-to-market for microalgal-based biorefineries.

Microbial consortia: a critical look at microalgae co-cultures for enhanced biomanufacturing

Monocultures have been the preferred production route in the bio-industry, where contamination has been a major bottleneck. In nature, microorganisms usually exist as part of organized communities and consortia, gaining benefits from co-habitation, keeping invaders at bay. There is increasing interest in the use of co-cultures to tackle contamination issues, and simultaneously increase productivity and product diversity. The feasibility of extending the natural phenomenon of co-habitation to the biomanufacturing industry in the form of co-cultures requires careful and systematic consideration of several aspects. This article will critically examine and review current work on microbial co-cultures, with the intent of examining the concept and proposing a design pipeline that can be developed in a biomanufacturing context.

Outdoor cultivation of Dunaliella salina KU 11 using brine and saline lake water with raceway ponds in northeastern Thailand

To evaluate the potential of algal biotechnology to replace traditional agriculture in northeastern Thailand, an open raceway cultivation system was developed to produce biomass and beta-carotene. Dunaliella salina KU 11 isolated from local saline soil was cultured in open raceway tanks using brine and saline lake water. Grown in modified Johnson's medium (with 2-3.5 M NaCl), the algae reached a maximum cell density on the fourth day (1.8 × 10⁶ cells mL^-1 ). Increasing KNO₃ and NaHCO₃ from 0.5 and 0.043 g L^-1 to 1 and 2.1 g L^-1 , respectively, significantly improved the yields of biomass (0.33 g L^-1 ) and beta-carotene (19 mg L^-1 ). Expected profits for algal production were evaluated, and it was found that this strain was suitable for outdoor cultivation and the developing algal industry in northeastern Thailand could produce high economic benefits (at least $64,120 per year per 0.16 ha).

Analysis of the Physiological and Molecular Responses of Dunaliella salina to Macronutrient Deprivation

The halotolerant chlorophyte Dunaliella salina can accumulate up to 10% of its dry weight as β-carotene in chloroplasts when subjected to adverse conditions, including nutrient deprivation. However, the mechanisms of carotenoid biosynthesis are poorly understood. Here, the physiological and molecular responses to the deprivation of nitrogen (-N), sulfur (-S), phosphorus (-P) and different combinations of those nutrients (-N-P, -N-S, -P-S and -N-P-S) were compared to gain insights into the underlying regulatory mechanisms of carotenoid biosynthesis. The results showed that both the growth and photosynthetic rates of cells were decreased during nutrient deprivation, accompanied by lipid globule accumulation and reduced chlorophyll levels. The SOD and CAT activities of the cells were altered during nutrient deprivation, but their responses were different. The total carotenoid contents of cells subjected to multiple nutrient deprivation were higher than those of cells subjected to single nutrient deprivation and non-stressed cells. The β-carotene contents of cells subjected to -N-P, -N-S and -N-P-S were higher than those of cells subjected to single nutrient deprivation. Cells subjected to sulfur deprivation accumulated more lutein than cells subjected to nitrogen and phosphorous deprivation. In contrast, no cumulative effects of nutrient deprivation on the transcription of genes in the carotenogenic pathway were observed because MEP and carotenogenic pathway genes were up-regulated during single nutrient deprivation but were downregulated during multiple nutrient deprivation. Therefore, we proposed that the carotenoid biosynthesis pathway of D. salina is regulated at both the transcriptional and posttranscriptional levels and that a complex crosstalk occurs at the physiological and molecular levels in response to the deprivation of different nutrients.

The Effects of Light, Temperature, and Nutrition on Growth and Pigment Accumulation of Three Dunaliella salina Strains Isolated from Saline Soil

Background:

Developing algal industries in saline-alkali areas is necessary. However, suitable strains and optimal production conditions must be studied before widespread commercial use.

Objectives:

The effects of light, temperature, KNO₃, and CO(NH₂)₂ on beta-carotene and biomass accumulation were compared and evaluated in order to provide scientific guidance for commercial algal production in northeastern Thailand.

Materials and Methods:

An orthogonal design was used for evaluating optimal conditions for the algal production of three candidate Dunaliella salina strains (KU XI, KU 10 and KU 31) which were isolated from saline soils and cultured in the column photobioreactor.

Results:

The optimal light and temperature for algae growth were 135.3 μmol m^-2 s^-1 and 22°C, while the conditions of 245.6 μmol m^-2 s^-1 and 22°C induced the highest level of beta-carotene production (117.99 mg L^-1). The optimal concentrations of KNO₃, CO(NH₂)₂, and NaHCO₃ for algae growth were 0.5 g L^-1, 0.36 g L^-1, and 1.5 g L^-1, respectively, while 0, 0.12 g L^-1 and 1.5 g L^-1 were best suited for beta-carotene accumulation. The highest beta-carotene rate per cell appeared with the highest light intensity (12.21 pg) and lowest temperature (12.47 pg), and the lowest total beta-carotene content appeared at the lowest temperature (15°C). There was not a significant difference in biomass accumulation among the three Dunaliella strains; however, the beta-carotene accumulation of KU XI was higher than that of the other two strains.

Conclusions:

Light and temperature were both relevant factors that contributed to the growth and beta-carotene accumulation of the three D. salina strains, and NaHCO₃ had significantly positive effects on growth. The degree of impact of the different factors on cell growth was temperature > NaHCO₃ > light intensity > KNO₃ > CO (NH₂)₂ > strains; the impact on beta-carotene accumulation was temperature > light intensity > KNO₃ > CO (NH₂)₂ > strains > NaHCO₃

Carotenoids in Microalgae

Carotenoids are a class of isoprenoids synthesized by all photosynthetic organisms as well as by some non-photosynthetic bacteria and fungi with broad applications in food, feed and cosmetics, and also in the nutraceutical and pharmaceutical industries. Microalgae represent an important source of high-value products, which include carotenoids, among others. Carotenoids play key roles in light harvesting and energy transfer during photosynthesis and in the protection of the photosynthetic apparatus against photooxidative damage. Carotenoids are generally divided into carotenes and xanthophyls, but accumulation in microalgae can also be classified as primary (essential for survival) and secondary (by exposure to specific stimuli).In this chapter, we outline the high value carotenoids produced by commercially important microalgae, their production pathways, the improved production rates that can be achieved by genetic engineering as well as their biotechnological applications.

Growth, antioxidant capacity and total carotene of Dunaliella salina DCCBC15 in a low cost enriched natural seawater medium

Dunaliella is currently drawing worldwide attention as an alternative source of nutraceuticals. Commercially, β-carotene making up over 10% of Dunaliella biomass is generating the most interest. These compounds, because of their non-toxic properties, have found applications in the food, drug and cosmetic industry. The β-carotene content of Dunaliella cells, however, depends heavily on the growth conditions and especially on the availability of nutrients, salinity, irradiance and temperature in the growth medium. A chemically well defined medium is usually required, which significantly contributes to the cost of pigment production; hence a desire for low cost marine media. The present study aimed at evaluating the suitability of six different media, especially exploiting local potential resources, for the mass production of Dunaliella salina DCCBC15 as functional food and medicine. The efficacy of a new selected low-cost enriched natural seawater medium (MD4), supplemented with industrial N-P-K fertilizer, was investigated with respect to biomass production, chlorophyll, antioxidant capacity, and total carotene by Dunaliella though culture conditions were not optimized yet. This new medium (MD4) appears extremely promising, since it affords a higher production of Dunaliella biomass and pigments compared with the control, a common artificial medium (MD1), while allowing a substantial reduction in the production costs. The medium is also recommended for culturing other marine algae.

Ettlia sp. YC001 showing high growth rate and lipid content under high CO2

Over 100 green-colored colonies were isolated from environmental samples when cultivating on a BG11 agar medium, and 4 strains showing different morphologies were selected based on light microscopic observation. Among these strains, the microalgal species with the highest growth rate under 10% CO(2) was identified as Ettlia sp. YC001 using an 18S rDNA-based phylogenetic analysis and morphological comparison. The highest cell density of 3.10 g/L (based on dry cell weight) and biomass productivity of 0.19 g/L/d were obtained under 5% CO(2) after 16 days. The lipid content and productivity were also up to 42% of the dry cell weight and 80.0mg/L/d, respectively. The color of the Ettlia sp. YC001 culture changed from green to red after a month due to the accumulation of certain carotenoids. Therefore, it would seem that Ettlia sp. YC001 is appropriate for mitigating CO(2) due to its high biomass productivity, and a suitable candidate for producing biodiesel and high-value products.

A novel potential source of β-carotene: Eustigmatos cf. polyphem (Eustigmatophyceae) and pilot β-carotene production in bubble column and flat panel photobioreactors

Carotenoids profile of the unicellular Eustigmatos cf. polyphem (Eustigmatophyceae) and β-carotene production of the microalga in bubble column and large flat panel bioreactors were studied. The microalga which contained β-carotene, violaxanthin and vaucheriaxanthin as the major carotenoids accumulated large amount of β-carotene. The β-carotene production of this microalga in the bubble column bioreactor was considerable, with the maximum intracellular β-carotene content reaching 60.76 mg g(-1), biomass reaching 9.2 g L(-1), and β-carotene yield up to 470.2 mg L(-1). The β-carotene productions in two large flat panel bioreactors were relatively lower, whereas over 100 mg β-carotene L(-1) was achieved. Besides, high light intensity helped to accumulate intracellular β-carotene and biomass. Deficient nitrate supply inhibited biomass growth, though it helped to accumulate β-carotene. Our results first proved that E. cf. polyphem was a potential source and producer of β-carotene, making it an interesting subject for further β-carotene study or commercial exploration.