Trachydiscus minutus, a new biotechnological source of eicosapentaenoic acid

Silvimonas soli sp. nov., a new member of Chromobacteriaceae isolated from soil in Norrbyskär island, Sweden

A novel bacterial species is described that was isolated from the soil of Norrbyskär island (Sweden). This Gram-negative, facultatively anaerobic and motile rod, designated 17-6T, was classified in the family Chromobacteriaceae, class Betaproteobacteria, and further characterized by a polyphasic approach. Comparative 16S rRNA gene analysis revealed the potential species novelty of the strain, with Silvimonas terrae (98.20 % similarity) and Silvimonas amylolytica (98.13 %) being its closest type strains. The phylogenetic novelty of the isolate at the level of species was confirmed using phylogenetic analyses based on the whole genome: average nucleotide identity values ranged from 79 to 81 %, average amino acid identity values from 75 to 81 % and percentage of conserved proteins values from 69-81 % with the members of genera Silvimonas and Amantichitinum. On the basis of phenotypic, phylogenetic, functional and genotypic analyses, we propose the isolate as the type strain of a novel species within the genus Silvimonas with the designation Silvimonas soli 17-6T (=DSM 115342T=CCM 9308T).

Solicola gregarius gen. nov., sp. nov., a soil actinobacterium isolated after enhanced cultivation with Micrococcus luteus culture supernatant

An actinobacterial strain, designated A5X3R13^T, was isolated from a compost soil suspension supplemented with extracellular material from a Micrococcus luteus-culture supernatant. The strain was cultured on tenfold-diluted reasoner's 2A agar. The cells were ovoid-to-rod shaped, non-motile, Gram-stain-positive, oxidase-negative, catalase-positive and had a width of 0.5 µm and a length of 0.8-1.2 µm. The results of both 16S rRNA-based phylogenetic and whole-genome analyses indicate that A5X3R13^T forms a distinct lineage within the family Nocardioidaceae (order Propionibacteriales). On the basis of the 16S rRNA gene sequence, A5X3R13^T was closely related to Aeromicrobium terrae CC-CFT486^T (96.2 %), Nocardioides iriomotensis IR27-S3^T (96.2 %), Nocardioides guangzhouensis 130^T (95.6 %), Marmoricola caldifontis YIM 730233^T (95.5 %), Aeromicrobium alkaliterrae KSL-107^T (95.4 %), Aeromicrobium choanae 9H-4^T (95.4 %), Aeromicrobium panaciterrae Gsoil 161^T (95.3 %), and Nocardioides jensenii NBRC 14755^T (95.2 %). The genome had a length of 4 915 757 bp, and its DNA G+C content was 68.5 mol %. The main fatty acids were 10-methyl C_17 : 0, C_16 : 0, C_15 : 0, C_18 : 0, C_17 : 0 and iso-C_16 : 0. The main polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and two unidentified phospholipids. MK-9(H₄) was the predominant respiratory quinone. The peptidoglycan type was A3γ (A41.1) and contained alanine, glycine, glutamic acid and ll-diaminopimelic acid in a molar ratio of 1.2 : 0.9 : 1.0 : 0.8. On the basis of the results of the phylogenetic and phenotypic analyses and comparisons with other members of the family Nocardioidaceae, strain A5X3R13^T is proposed to represent a novel species within a novel genus, for which the name Solicola gregarius gen. nov., sp. nov. is proposed. The type strain is A5X3R13^T (=DSM 112953^T=NCCB 100840^T).

Auxin supplementation under nitrogen limitation enhanced oleic acid and MUFA content in Eustigmatos calaminaris biomass with potential for biodiesel production

Due to their lipid accumulation potential, microalgae are widely studied in terms of their use in the production of biodiesel. The present study was focused on determination of changes in the biomass production, biochemical composition, accumulation and distribution of fatty acids in neutral lipids, glycolipids, phospholipids and biodiesel properties of soil microalga Eustigmatos calaminaris in response to various levels of nitrogen stress and indole-3-acetic acid supplementation. The highest growth rate, the highest lipid content and daily lipid productivity were noted at the nitrogen limitation up to 25% with IAA supplementation. The increase in NL was associated with nutrient stress. An increase in the level of GL and PL were recorded upon the reduction of the nitrogen content (25% N) and the addition of IAA. The gas chromatography/mass spectrometry analysis demonstrated that C16:0, C16:1, and C18:1 were the main fatty acids in E. calaminaris lipids. As shown by the lipidomic analysis, the IAA supplementation in the nitrogen limitation variants enhanced the content of TAGs in C18:1 and monounsaturated fatty acids. The current findings indicated a potential strategy to improve the fatty acid profile in neutral lipids and high potential of E. calaminaris for biodiesel applications.

Pedomonas mirosovicensis gen. nov., sp. nov., a bacterium isolated from soil with the aid of Micrococcus luteus culture supernatant containing resuscitation-promoting factor

An orange-golden iridescent culture, designated A1X5R2T, was isolated from a compost soil suspension which was amended with Micrococcus luteus NCTC 2665T culture supernatant. The cells were non-motile, Gram-stain-negative, 0.4–0.5 µm wide and 0.7–1.4 µm long. The 16S rRNA-based phylogenetic and whole-genome analyses revealed that strain A1X5R2T forms a distinct lineage within the family Sphingosinicellaceae and is closely related to members of the genus Sphingoaurantiacus ( S. capsulatus , 93.04 % similarity, and S. polygranulatus , 92.77 %). The organism grew at 22–47 °C (optimal at 37 °C), salinity <3 % (optimal at 1.5 %) and at pH 7. The major respiratory quinone was ubiquinone-10, but a small quantity of ubiquinone-9 was also detected The major polyamine was homospermidine, but a small quantity of putrescine was also detected. The strain contained C18  :  1ω7c, C16 : 0, C16 : 1 ω7c and C18 : 0 as the major fatty acids. The main polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, sphingoglycolipid, diphosphatidylglycerol, two unidentified phospholipids and three unidentified amino lipids. The DNA G+C content was 64.9 mol%. According to the results of phylogenetic and phylogenomic analyses, as well as its physiological characteristics, strain A2X5R2T represents the type species of a novel genus within the family Sphingosinicellaceae . The name Pedomonas mirosovicensis gen. nov., sp. nov. is proposed, with the type strain being A1X5R2T (=NCCB 100839T=DSM 112829T).

Potential of microalgae as source of health-beneficial bioactive components in produced eggs

In line with the growing interest in humans' nutrition, production of microalgae-based functional foods characterized by an increased content of bioactive substances is attractive. The aim of this study was to investigate the potential of microalgae as additives to feed for laying hens, to enrich the eggs with polyunsaturated fatty acids (PUFA) and selenium/carotenoid antioxidants. Our results showed that supplementation of hens by feed containing 1% of Trachydiscus minutus or 1% of Japonochytrium marinum leads to increase of long-chain PUFA in eggs by 26-66%. Addition of 1% of Scenedesmus obliquus to feed causes the increase of lutein and cantaxanthin in eggs by 48% and 18%, respectively, and addition of 0.5% selenium enriched Chlorella vulgaris increases the final content of organic selenium in eggs by 100-152%. As concerns selenium, it is important to notice that its bioavailability has to be considered. Despite the higher concentration of total selenium in Vischeria helvetica than in C. vulgaris, its bioaccessibility in Vischeria was limited, thus out of usage for feeding purposes. Administration of combinations of selenium enriched Chlorella + Japonochytrium and Chlorella + Schizochitrium verified the increased concentrations of organic selenium, PUFA, as well as carotenoids, with no adverse effect on quality and productivity of eggs. The study confirmed the potential of both traditional as well as new microalgae to be used as feed supplements for functional eggs production. The supplementation of hens by specific microalgae combinations could be advantageous in terms of spectrum of bioactive compounds present.

Fatty Acids Derivatives From Eukaryotic Microalgae, Pathways and Potential Applications

The exploitation of petrochemical hydrocarbons is compromising ecosystem and human health and biotechnological research is increasingly focusing on sustainable materials from plants and, to a lesser extent, microalgae. Fatty acid derivatives include, among others, oxylipins, hydroxy fatty acids, diols, alkenones, and wax esters. They can occur as storage lipids or cell wall components and possess, in some cases, striking cosmeceutical, pharmaceutical, and nutraceutical properties. In addition, long chain (>20) fatty acid derivatives mostly contain highly reduced methylenic carbons and exhibit a combustion enthalpy higher than that of C_14–20 fatty acids, being potentially suitable as biofuel candidates. Finally, being the building blocks of cell wall components, some fatty acid derivatives might also be used as starters for the industrial synthesis of different polymers. Within this context, microalgae can be a promising source of fatty acid derivatives and, in contrast with terrestrial plants, do not require arable land neither clean water for their growth. Microalgal mass culturing for the extraction and the exploitation of fatty acid derivatives, along with products that are relevant in nutraceutics (e.g., polyunsaturated fatty acids), might contribute in increasing the viability of microalgal biotechnologies. This review explores fatty acids derivatives from microalgae with applications in the field of renewable energies, biomaterials and pharmaceuticals. Nannochloropsis spp. (Eustigmatophyceae, Heterokontophyta) are particularly interesting for biotechnological applications since they grow at faster rates than many other species and possess hydroxy fatty acids and aliphatic cell wall polymers.

Photoautotrophic production of eicosapentaenoic acid

Eicosapentaenoic acid (EPA) is an omega-3 fatty acid which is an essential nutrient for both humans and animals. This review examines the global need for EPA, both in human nutrition and aquaculture. The potential shortfall in supply of this important nutrient as well as sustainability issues with wild-caught fish have generated increased interest into alternative sources of EPA. Various approaches are summarized, including heterotrophic production and the use of genetically modified microorganisms and plants. Studies on photoautotrophic production of EPA are extensively reviewed. Widely used species for large-scale production of EPA includes Phaeodactylum tricornutum and Nannochloropsis due to their robustness and relatively high growth rates and EPA content (typically 5% of dry biomass). Approaches for large-scale production have also been reviewed. Closed reactors like flat panels, tubular reactors and bubble columns may be the most suitable due to their high productivity. However, there is no agreement in the literature as to which design generates the lowest cost of production. The economics of the process has also been examined. The best estimates for large-scale (100 hectare) plants give EPA prices of the order 39-90 USD per kilogram. This is approximately ten times higher than the price of EPA derived from fish oil. Potential avenues for lowering the cost are highlighted, along with the need to better understand the advantages and disadvantages of different EPA production methods from a more holistic perspective.

Effect of Food with Low Enrichment of N-3 Fatty Acids in a Two-Month Diet on the Fatty Acid Content in the Plasma and Erythrocytes and on Cardiovascular Risk Markers in Healthy Young Men

Polyunsaturated fatty acids of the n-3 series (n-3 PUFA) exhibit a number of favorable effects on the human organism and it is desirable to increase their intake in the diet. For this purpose, flaxseed oil was added to a chicken-feed mixture for the production of meat and eggs. The content of n-3 PUFA in the obtained meat was increased from 250 mg (reference value) to 900 mg in 100 g of meat and from 110 mg (reference value) to 190 mg in 100 g of whole egg; the enriched products are designated as omega-3 meat and omega-3 eggs. Omega-3 meat and eggs were subsequently fed for a period of eight weeks in an amount of 480 g of meat and four eggs (228 g netto) a week to a group of 14 healthy volunteers, whose body composition parameters were measured and blood was analyzed biochemically to determine blood lipids, coagulation parameters, plasma, and erythrocyte fatty acid spectrum composition. A control group of 14 volunteers was fed normal chicken and eggs in the same regime. The performed dietary intervention increases the intake of long-chain PUFA (LC-PUFA) by 37 mg per day, which represents 7–15% of the recommended daily dose. The performed tests demonstrated that the consumption of omega-3 enriched meat and eggs significantly increases the content of n-3 PUFA in the erythrocytes, which are a long-term indicator of fatty acid intake. This intervention has no demonstrable effect on the basic body parameters, such as body weight, fat content, Body Mass Index (BMI), and also on the plasma cholesterol level, high-density lipoprotein (HDL), low-density lipoprotein (LDL), blood clotting and inflammation markers, and omega-3 index.

Algae: Critical Sources of Very Long-Chain Polyunsaturated Fatty Acids

Polyunsaturated fatty acids (PUFAs), which are divided into n-3 and n-6 classes, are essential for good health in humans and many animals. They are metabolised to lipid mediators, such as eicosanoids, resolvins and protectins. Increasing interest has been paid to the 20 or 22 carbon very long chain PUFAs, since these compounds can be used to form lipid mediators and, thus, avoid inefficient formation of dietary plant PUFAs. The ultimate sources of very long chain PUFAs are algae, which are consumed by fish and then by humans. In this review, I describe the biosynthesis of very long chain PUFAs by algae and how this synthesis can be manipulated for commercial purposes. Ultimately, the production of algal oils is critical for ecosystems worldwide, as well as for human dietary lipids.

Pseudogemmobacter bohemicus gen. nov., sp. nov., a novel taxon from the Rhodobacteraceae family isolated from heavy-metal-contaminated sludge

The creamy white to beige, aerobic, non-motile, ovoid to rod-shaped, Gram-stain-negative strain, Cd-10^T, was isolated from heavy-metal-contaminated sludge from a decantation basin of a heavy metal processing factory based on its ability to tolerate CdCl2 in the cultivation medium. In the reconstruction of its phylogeny based on 16S rRNA gene sequences, strain Cd-10^T clustered with species of the genera Gemmobacter, Xinfangfangia, Tabrizicola and Rhodobacter within the family Rhodobacteraceae. Its 16S rRNA gene sequence exhibited 96.32 % pairwise similarity to the type strain of Xinfangfangia soli, 95.3 % to that of Gemmobacter intermedius, followed by Tabrizicola fusiformis (95.10 %), Rhodobacter sediminis (94.88 %), Gemmobacter nectariphilus and Rhodobacter capsulatus (both 94.81 %). The major respiratory quinone was Q-10 accompanied by Q-9, the fatty acid profile consisted predominantly of C18 : 1ω7c, C18 : 0, C16 : 0 and C16 : 1ω7c, the major polar lipids were phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylcholine and diphosphatidylglycerol. An analysis of the percentage of conserved proteins deduced from draft or complete genomic sequences of strain Cd-10^T and representatives of its closest relatives suggested that strain Cd-10^T is a member of a novel genus within the Rhodobacteraceae family for which we propose the name Pseudogemmobacter. Strain Cd-10^T (=DSM 103618^T=NCCB 100645^T) is the type strain of Pseudogemmobacter bohemicus gen. nov., sp. nov., the type species of the genus Pseudogemmobacter gen. nov.

The lipid biochemistry of eukaryotic algae

Algal lipid metabolism fascinates both scientists and entrepreneurs due to the large diversity of fatty acyl structures that algae produce. Algae have therefore long been studied as sources of genes for novel fatty acids; and, due to their superior biomass productivity, algae are also considered a potential feedstock for biofuels. However, a major issue in a commercially viable "algal oil-to-biofuel" industry is the high production cost, because most algal species only produce large amounts of oils after being exposed to stress conditions. Recent studies have therefore focused on the identification of factors involved in TAG metabolism, on the subcellular organization of lipid pathways, and on interactions between organelles. This has been accompanied by the development of genetic/genomic and synthetic biological tools not only for the reference green alga Chlamydomonas reinhardtii but also for Nannochloropsis spp. and Phaeodactylum tricornutum. Advances in our understanding of enzymes and regulatory proteins of acyl lipid biosynthesis and turnover are described herein with a focus on carbon and energetic aspects. We also summarize how changes in environmental factors can impact lipid metabolism and describe present and potential industrial uses of algal lipids.

The plastid genome of some eustigmatophyte algae harbours a bacteria-derived six-gene cluster for biosynthesis of a novel secondary metabolite

Acquisition of genes by plastid genomes (plastomes) via horizontal gene transfer (HGT) seems to be a rare phenomenon. Here, we report an interesting case of HGT revealed by sequencing the plastomes of the eustigmatophyte algae Monodopsis sp. MarTras21 and Vischeria sp. CAUP Q 202. These plastomes proved to harbour a unique cluster of six genes, most probably acquired from a bacterium of the phylum Bacteroidetes, with homologues in various bacteria, typically organized in a conserved uncharacterized putative operon. Sequence analyses of the six proteins encoded by the operon yielded the following annotation for them: (i) a novel family without discernible homologues; (ii) a new family within the superfamily of metallo-dependent hydrolases; (iii) a novel subgroup of the UbiA superfamily of prenyl transferases; (iv) a new clade within the sugar phosphate cyclase superfamily; (v) a new family within the xylose isomerase-like superfamily; and (vi) a hydrolase for a phosphate moiety-containing substrate. We suggest that the operon encodes enzymes of a pathway synthesizing an isoprenoid–cyclitol-derived compound, possibly an antimicrobial or other protective substance. To the best of our knowledge, this is the first report of an expansion of the metabolic capacity of a plastid mediated by HGT into the plastid genome.

Algae as nutritional and functional food sources: revisiting our understanding

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.

Coccomyxa actinabiotis sp. nov. (Trebouxiophyceae, Chlorophyta), a new green microalga living in the spent fuel cooling pool of a nuclear reactor

Life can thrive in extreme environments where inhospitable conditions prevail. Organisms which resist, for example, acidity, pressure, low or high temperature, have been found in harsh environments. Most of them are bacteria and archaea. The bacterium Deinococcus radiodurans is considered to be a champion among all living organisms, surviving extreme ionizing radiation levels. We have discovered a new extremophile eukaryotic organism that possesses a resistance to ionizing radiations similar to that of D. radiodurans. This microorganism, an autotrophic freshwater green microalga, lives in a peculiar environment, namely the cooling pool of a nuclear reactor containing spent nuclear fuels, where it is continuously submitted to nutritive, metallic, and radiative stress. We investigated its morphology and its ultrastructure by light, fluorescence and electron microscopy as well as its biochemical properties. Its resistance to UV and gamma radiation was assessed. When submitted to different dose rates of the order of some tens of mGy · h^-1 to several thousands of Gy · h^-1 , the microalga revealed to be able to survive intense gamma-rays irradiation, up to 2,000 times the dose lethal to human. The nuclear genome region spanning the genes for small subunit ribosomal RNA-Internal Transcribed Spacer (ITS) 1-5.8S rRNA-ITS2-28S rRNA (beginning) was sequenced (4,065 bp). The phylogenetic position of the microalga was inferred from the 18S rRNA gene. All the revealed characteristics make the alga a new species of the genus Coccomyxa in the class Trebouxiophyceae, which we name Coccomyxa actinabiotis sp. nov.

Bioprospecting of microalgae: Proper extraction followed by high performance liquid chromatographic-high resolution mass spectrometric fingerprinting as key tools for successful metabolom characterization

Currently, the interest in microalgae as a source of biologically active components exploitable as supplementary ingredients to food/feed or in cosmetics continues to increase. Existing research mainly aims to focus on revealing and recovering the rare, cost competitive components of the algae metabolom. Because these components could be of very different physicochemical character, a universal approach for their isolation and characterization should be developed. This study demonstrates the systematic development of the extraction strategy that represents one of the key challenges in effective algae bioprospecting, which predefines their further industrial application. By using of Trachydiscus minutus as a model microalgae biomass, following procedures were tested and critically evaluated in order to develop the generic procedure for microalgae bioprospecting: (i) various ways of mechanical disintegration of algae cells enabling maximum extraction efficiency, (ii) the use of a wide range of extraction solvents/solvent mixtures suitable for optimal extraction yields of polar, medium-polar, and non-polar compounds, (iii) the use of consecutive extractions as a fractionation approach. Within the study, targeted screening of selected compounds representing broad range of polarities was realized by ultra-high performance liquid chromatography coupled with high resolution tandem mass spectrometric detection (UHPLC-HRMS/MS), to assess the effectiveness of undertaken isolation steps. As a result, simple and high-throughput extraction-fractionation strategy based on consecutive extraction with water-aqueous methanol-hexane/isopropanol was developed. Moreover, to demonstrate the potential of the UHPLC-HRMS/MS for the retrospective non-target screening and compounds identification, the collected mass spectra have been evaluated to characterize the pattern of extracted metabolites. Attention was focused on medium-/non-polar extracts and characterization of lipid species present in the T. minutus algae. Such detailed information on the composition of native (non-hydrolyzed) lipids of this microalga has not been published yet.

Microalgae as a Source for VLC-PUFA Production

Microalgae present a huge and still insufficiently tapped resource of very long-chain omega-3 and omega-6 polyunsaturated fatty acids (VLC-PUFA) for human nutrition and medicinal applications. This chapter describes the diversity of unicellular eukaryotic microalgae in respect to VLC-PUFA biosynthesis. Then, we outline the major biosynthetic pathways mediating the formation of VLC-PUFA by sequential desaturation and elongation of C18-PUFA acyl groups. We address the aspects of spatial localization of those pathways and elaborate on the role for VLC-PUFA in microalgal cells. Recent progress in microalgal genetic transformation and molecular engineering has opened the way to increased production efficiencies for VLC-PUFA. The perspectives of photobiotechnology and metabolic engineering of microalgae for altered or enhanced VLC-PUFA production are also discussed.

Taxonomic study of a new eustigmatophycean alga, Vacuoliviride crystalliferum gen. et sp. nov

This study investigated the taxonomic affiliation of the algal strain nak-9, which has been reported to absorb radioactive cesium with high efficiency, using light and electron microscopy, and molecular phylogenetic analysis based on 18S ribosomal RNA gene (rDNA) sequences. This alga is spherical and coccoid, with a smooth cell wall, large vacuole, crystalline structure, reddish globule, and refractile granules (lamellate vesicles). The cells possess one to several greenish parietal chloroplasts with a bulging pyrenoid surrounded by lamellate vesicles. The chloroplasts include orderly thylakoid lamellae but no girdle lamella. Molecular phylogenetic analysis suggests that strain nak-9 is a member of the eustigmatophycean clade, which includes Goniochloris, Pseudostaurastrum, and Trachydiscus. On the basis of these results, we propose that strain nak-9 (NIES-2860) comprises a new species and new genus of the Eustigmatophyceae, Vacuoliviride crystalliferum gen. et sp. nov.

Temperature dependence of production of structured triacylglycerols in the alga Trachydiscus minutus

This study describes the identification of regioisomers and enantiomers of triacylglycerols of C20 polyunsaturated fatty acids (PUFAs) in the alga Trachydiscus minutus cultivated at different temperatures using reversed- and chiral-phase liquid chromatography-mass spectrometry. The use of the two different phases contributes to ready identification, both qualitative and semiquantitative, of regioisomers and enantiomers of triacylglycerols containing eicosapentaenoic and arachidonic in the molecule. The ratio of regioisomers and enantiomers of triacylglycerols (TAG) depends on the temperature of cultivation; with lowering temperature the proportion of the achiral TAG increases and the enantiomer ratio diverges from 1:1.

The microalga Parachlorella kessleri--a novel highly efficient lipid producer

The alga Parachlorella kessleri, strain CCALA 255, grown under optimal conditions, is characterized by storage of energy in the form of starch rather than lipids. If grown in the complete medium, the cultures grew rapidly, producing large amounts of biomass in a relatively short time. The cells, however, contained negligible lipid reserves (1-10% of DW). Treatments inducing hyperproduction of storage lipids in P. kessleri biomass were described. The cultures were grown in the absence or fivefold decreased concentration of either nitrogen or phosphorus or sulfur. Limitation by all elements using fivefold or 10-fold diluted mineral medium was also tested. Limitation with any macroelement (nitrogen, sulfur, or phosphorus) led to an increase in the amount of lipids; nitrogen limitation was the most effective. Diluted nutrient media (5- or 10-fold) were identified as the best method to stimulate lipid overproduction (60% of DW). The strategy for lipid overproduction consists of the fast growth of P. kessleri culture grown in the complete medium to produce sufficient biomass (DW more than 10 g/L) followed by the dilution of nutrient medium to stop growth and cell division by limitation of all elements, leading to induction of lipid production and accumulation up to 60% DW. Cultivation conditions necessary for maximizing lipid content in P. kessleri biomass generated in a scale-up solar open thin-layer photobioreactor were described.

ZOOSPOROGENESIS, MORPHOLOGY, ULTRASTRUCTURE, PIGMENT COMPOSITION, AND PHYLOGENETIC POSITION OF TRACHYDISCUS MINUTUS (EUSTIGMATOPHYCEAE, HETEROKONTOPHYTA)(1)

The traditional order Mischococcales (Xanthophyceae) is polyphyletic with some original members now classified in a separate class, Eustigmatophyceae. However, most mischococcalean species have not yet been studied in detail, raising the possibility that many of them still remain misplaced. We established an algal culture (strain CCALA 838) determined as one such species, Trachydiscus minutus (Bourr.) H. Ettl, and studied the morphology, ultrastructure, life cycle, pigment composition, and phylogeny using the 18S rRNA gene. We discovered a zoosporic part of the life cycle of this alga. Zoospore production was induced by darkness, suppressed by light, and was temperature dependent. The zoospores possessed one flagellum covered with mastigonemes and exhibited a basal swelling, but a stigma was missing. Ultrastructural investigations of vegetative cells revealed plastids lacking both a connection to the nuclear envelope and a girdle lamella. Moreover, we described biogenesis of oil bodies on the ultrastructural level. Photosynthetic pigments of T. minutus included as the major carotenoids violaxanthin and vaucheriaxanthin (ester); we detected no chl c. An 18S rRNA gene-based phylogenetic analysis placed T. minutus in a clade with species of the genus Pseudostaurastrum and with Goniochloris sculpta Geitler, which form a sister branch to initially studied Eustigmatophyceae. In summary, our results are inconsistent with classifying T. minutus as a xanthophycean and indicate that it is a member of a novel deep lineage of the class Eustigmatophyceae.

RESPONSE OF TRACHYDISCUS MINUTUS (XANTHOPHYCEAE) TO TEMPERATURE AND LIGHT(1)

The effects of different temperatures and light intensities on growth, pigments, sugars, lipids, and proteins, as well as on some antioxidant and proteolytic enzymes of Trachydiscus minutus (Bourr.) H. Ettl, were investigated. The optimum growth temperature and light intensity were 25°C and 2 × 132 μmol photons · m(-2 ) · s(-1) , respectively. Under these conditions, proteins were the main biomass components (33.45% dry weight [dwt]), with high levels of carbohydrates (29% dwt) and lipids (21.77% dwt). T. minutus tolerated temperatures between 20°C and 32°C, with only moderate changes in cell growth and biochemical composition. Extremely low (15°C) and high (40°C) temperatures decreased chl and RUBISCO contents and inhibited cell growth. The biochemical response of the alga to both unfavorable conditions was an increase in lipid content (up to 35.19% dwt) and a decrease in carbohydrates (down to 13.64% dwt) with much less of a change in total protein content (in the range of 30.51%-38.13% dwt). At the same time, the defense system of T. minutus was regulated differently in response to heat or cold treatments. Generally, at 40°C, the activities of superoxide dismutase (SOD), catalase (CAT), and proteases were drastically elevated, and three polypeptides were overexpressed, whereas the glutathione reductase (GR) and peroxidase (POD) activities were reduced. In contrast, at 15°C, all these enzymes except GR were suppressed. The effect of light was to enhance or decrease the temperature stress responses, depending on intensity. Our studies demonstrate the broad temperature adaptability of T. minutus as well as the potential for the production of valuable algal biomass.

Effect of nitrogen and phosphorus starvation on the polyunsaturated triacylglycerol composition, including positional isomer distribution, in the alga Trachydiscus minutus

The yellow-green alga Trachydiscus minutus (Eustigmatophyceae, Heterocontophyta) was cultivated in a standard medium and under nitrogen- and phosphorus-starvation and its triacylglycerols were analyzed by RP-HPLC/MS-APCI. The molecular species of triacylglycerols included a total of 74 triacylglycerols having at least one polyunsaturated fatty acid. Polyunsaturated triacylglycerols were identified for the first time in a yellow-green alga. N-starvation brought about a nearly 50% drop in TAGs containing EPA, and also decreased TAGs containing ARA, while P-starvation had a sizable effect on those TAGs that contain two or three arachidonic acids. In four TAGs containing PUFA, i.e. EEE, EEA, EAA and AAA, N-starvation caused a rapid fivefold increase in ARA content and the ratio of TAGs containing ARA, i.e. AEE to AAA increased tenfold relative to control. Regioisomeric characterization of triacylglycerols containing palmitic, arachidonic (ARA) and eicosapentaenoic acids (EPA) showed that the proportion of positional isomers is affected by N- and P-starvation. N- and P-starvation also changed the ratio of symmetrical to asymmetrical TAGs. Positional isomers exhibited identical ratios of symmetrical and asymmetrical TAGs irrespective of the type of FAs. In control cultivation the major TAGs with a single PUFA were symmetrical ones (PEP or PAP) whose ratio to asymmetrical counterparts (PPE or PPA) was about 3:1, whereas N- and P-starvation yielded opposite ratios, 1:3-1:5. The control cultivation yielded ~90% asymmetrical TAGs with two PUFAs (i.e. PEE and PAA), whereas with N- and P-starvation the ratio of symmetrical to asymmetrical TAGs increased to 2:1 and 3:2, respectively.

LC-PUFA from photosynthetic microalgae: occurrence, biosynthesis, and prospects in biotechnology

Microalgae offer potential for numerous commercial applications, among them the production of long-chain polyunsaturated fatty acids (LC-PUFAs). These valuable fatty acids are important for a variety of nutraceutical and pharmaceutical purposes, and the market for these products is continually growing. An appropriate ratio of LC-PUFA of the ω-3 and ω-6 groups is vital for "healthy" nutrition, and adequate dietary intake has strong health benefits in humans. Microalgae of diverse classes are primary natural producers of LC-PUFA. This mini-review presents an introductory overview of LC-PUFA-related health benefits in humans, describes LC-PUFA occurrence in diverse microalgal classes, depicts the major pathways of their biosynthesis in microalgae, and discusses the prospects for microalgal LC-PUFA production.

Raman microspectroscopy of individual algal cells: sensing unsaturation of storage lipids in vivo

Algae are becoming a strategic source of fuels, food, feedstocks, and biologically active compounds. This potential has stimulated the development of innovative analytical methods focused on these microorganisms. Algal lipids are among the most promising potential products for fuels as well as for nutrition. The crucial parameter characterizing the algal lipids is the degree of unsaturation of the constituent fatty acids quantified by the iodine value. Here we demonstrate the capacity of the spatially resolved Raman microspectroscopy to determine the effective iodine value in lipid storage bodies of individual living algal cells. The Raman spectra were collected from three selected algal species immobilized in an agarose gel. Prior to immobilization, the algae were cultivated in the stationary phase inducing an overproduction of lipids. We employed the characteristic peaks in the Raman scattering spectra at 1,656 cm⁻¹ (cis C═C stretching mode) and 1,445 cm⁻¹ (CH₂ scissoring mode) as the markers defining the ratio of unsaturated-to-saturated carbon-carbon bonds of the fatty acids in the algal lipids. These spectral features were first quantified for pure fatty acids of known iodine value. The resultant calibration curve was then used to calculate the effective iodine value of storage lipids in the living algal cells from their Raman spectra. We demonstrated that the iodine value differs significantly for the three studied algal species. Our spectroscopic estimations of the iodine value were validated using GC-MS measurements and an excellent agreement was found for the Trachydiscus minutus species. A good agreement was also found with the earlier published data on Botryococcus braunii. Thus, we propose that Raman microspectroscopy can become technique of choice in the rapidly expanding field of algal biotechnology.