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Long-chain alkenones (LCAs) produced by phylogenetically classified Groups 1 and 3 Isochrysidales are increasingly used for paleotemperature and/or paleosalinity reconstructions in oligohaline lakes and marine environments. However, there are considerable difficulties in the paleoenvironmental interpretation of LCAs from Group 2 Isochrysidales thriving in saline lakes. The biggest challenge lies in our poor understanding of the complexity and ecological niches of individual Group 2 subclades in saline lakes. Here, we perform comprehensive analysis of haptophyte-specific 18S rRNA sequences and distributions of LCAs, and long-chain alkenoates (LCEs) in surface sediments and suspended particulate matter (SPM) from 37 saline lakes in northern China. These lakes span a large salinity gradient from 0.5 to 308‰. Combined with published genomic data of Group 2 Isochrysidales, our phylogenetic analysis reveals three Group 2 subclades occupying distinct ecological niches: one ice-related bloomer Group 2i and two warm-season bloomers Groups 2w1 and 2w2. Group 2i, the earliest seasonal bloomer, frequently co-occurs with Group 2w1 in sediments from saline lakes with relatively low to intermediate salinity waters, whereas Group 2w2 blooms in hypersaline waters. Based on existing data, C39:4 methyl alkenone is a chemotaxonomic biomarker for Group 2i. %C37:4 (relative abundance of C37:4 to the total C37 alkenones) values in the three Group subclades follow the order: Group 2i > Group 2w2 > Group 2w1. The %C37:4 in sediment cores of saline lakes does not directly record past salinity changes, but instead reflects variable contributions in production by these three subclades. This could indirectly and partially reflect overall salinity changes in some lakes dominated by Groups 2i and 2w1, but can be more complicated in lakes dominated by other assemblages. For our sites, we also demonstrate that direct use of C37 alkenone unsaturation indices ( U 37 K , U 37 K ' , and U 37 K ' ' ) for paleotemperature reconstructions in saline lakes is generally not feasible, except for cases where alkenone-producing Isochrysidales are dominated by one single species/subclade and seasonal production effects can be circumvented. We propose two possible alternative proxies for paleotemperature reconstructions in saline lakes: 1) unsaturation ratios of C41 and C42 alkenones, as these compounds are predominantly produced by a limited number of Group 2 species, such as Isochrysis nuda ( Liao et al., 2020 ); 2) C38Et/C36OEt ratio (ratio of C38 ethyl alkenones and C36 ethyl alkenoates), which appears to have similar temperature sensitivity for Groups 2w1 and 2w2, in lakes with no Group 2i inputs. Our study provides new insights into the phylogenetic classifications of Group 2 Isochrysidales and their ecological/environmental niches, which are fundamental for more quantitative and rigorous applications of LCAs and LCEs in saline lakes as paleosalinity and paleotemperature proxies.

The study examined different types of organic manure on the culture of marine plankton as a potential source of food for rabbitfish, Siganus stellatus, larvae. Cow dung showed significantly higher species abundance and diversity of cultured marine plankton followed by chicken and finally mixed media manure (p

Novel nutritional/functional applications of Isochrysis strains are mostly based on their diversified lipid classes. The content of these lipids is modulated by different factors, among which salinity has been comparatively understudied. Since managing salinity is key for optimal microalgae outdoor mass production and most studied Isochrysis strains are marine, the lipid response to nearly extreme hypo and hyper salinity in a new estuarine strain is here described. Total lipids in exponentially grown Isochrysis galbana VLP gradually decreased from 334 ± 36.6 mg g-1 at a salinity of 5 psu to 164.3 ± 24.4 mg g-1 at 50 psu. Present is the first report on lipid class (LC) remodeling in response to salinity in any Isochrysis strain. Two main storage lipids, steryl esters (SE) and triacylglycerol (TAG), underwent the fastest absolute decrease as salinity increased during both active and halted growth in the estuarine strain I. galbana VLP. Alkenones also decreased with salinity although less markedly. Among photosynthetic lipids, galactolipids were more affected by salinity than the anionic lipids. Salinity had minor influence on the relative sterol and betaine lipid proportions. Salinity explained more of total LC variation (34.6%) than culture stage (30.3%), whereas the opposite occurred with fatty acid (FA) variation. The main FA affected by salinity were 20:5n-3, 18:3n-3, 18:5n-3 and 18:2n-6. Nutritional value of I. galbana VLP from 5 psu exponential cultures was 1.5-fold to 2-fold higher than under all other conditions. Isochrysis production in low salinity waters can be a sustainable procedure compatible with its optimized nutritional value.

The paracalanid copepod,Bestiolina amoyensis, is a widely distributed species occurring in subtropical inshore waters across the Pacific Ocean. Its small size, herbivorous feeding habit, and high adaptability make the species one of the most promising candidates as potential live feed for hatchery larval rearing. This study investigated effects of different feeding density of microalgaeIsochrysisspp. (1 × 105, 2 × 105, 3 × 105, 4 × 105, and 5 × 105cells ml–1) and photoperiod (8L:16D, 12L:12D, and 16L:8D) on productivity-related parameters, including egg production, female life expectancy and population dynamics ofB. amoyensis. Results showed that total egg output over female lifespan, final population size and intrinsic rate of population of 12L:12D photoperiod treatments were always the highest among three photoperiod conditions, especially at the food concentration of 4 × 105cells ml–1, indicatingB. amoyensishad high reproductive performance and the population was in a more stable status. The number of nauplii from 4 × 105cells ml–1algal concentration treatment accounted for 75% of the population, and the ratio of females to males approaching 1:1 when photoperiod was 12L:12D; female life expectancy was 10.5 ± 0.6 days. In conclusion, our results showed thatIsochrysisspp. is a suitable feed forB. amoyensiswith an optimal concentration at 4 × 105cells mL–1; the optimal photoperiod forB. amoyensisrearing is 12L:12D. The relatively long reproductive lifespan and high intrinsic population increase rate makeB. amoyensisa good candidate to develop culture techniques for hatchery larval rearing.

International audience; Shellfish farming, a key sector of French aquaculture activity, allows the production of oyster spat in a controlled environment. Their production in commercial hatcheries requires control over the quality of the seawater used to sustain crossbreeding, breeding, and the production of fodder microalgae. Therefore, improving the filtration conditions of incoming water is crucial in ensuring the sustainability of production. An ultrafiltration pilot plant was therefore installed at Vendee Naissain. This ultrafiltration pilot plant allows filtration at 0.02 mu m; it is used upstream of hatcheries to eliminate pathogens and parasites that can influence the development of cultivated species and downstream to remove oyster gametes in hatchery effluents. The objectives of this work were: (i) to use ultrafiltered seawater for the culture of the microalga Isochrysis lutea (T-Iso) to determine whether better growth than that observed with borehole water, historically used by the producer, can be achieved; and (ii) to determine whether the use of ultrafiltered water results in better fertilization rates of the cupped oyster Crassostrea gigas compared to filtered and UV-treated seawater. Ultrafiltered water has shown definite efficiency for culturing T-Iso with rapid growth and significant reduction in contamination compared to cultivation in well water. The contribution of ultrafiltered water in hatching is more nuanced; ultrafiltered water does not stabilize hatch rates, and its quality is highly dependent on the quality of the seawater used.

Aim This study investigated the effect of several metabolic enhancers on the expression of fatty acid biosynthetic genes and their influence on the production of high-value PUFA in the marine microalgae Isochrysis sp., CASA CC 101. Methods and Results The effect of the presence of iron (Fe), nicotinic acid (NIC), methyl jasmonate (MJ) and thidiazuron (TDZ) on the expression of the fatty acid desaturase genes Δ6Des, Δ5Des and Δ4Des was studied in cultures of the marine microalga Isochrysis sp., CASA CC 101. The production of high-value PUFA like γ-linolenic acid (GLA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was correlated with these gene expressions. The results showed that MJ, Fe and TDZ significantly increased the lipid content than the control. MJ specifically up-regulated ∆6Des gene expression and thereby increased GLA production. Whereas Fe specifically increased ∆5Des gene expression and thereby increased EPA production. However, Fe and TDZ-treated cells effectively upregulated the expression of ∆4Des and increased the production of DHA when compared with control cells. Conclusions Our findings suggest that addition of Fe and MJ in the culture medium triggers the expression of PUFA biosynthetic genes, especially ∆6Des and ∆4Des, in marine microalga Isochrysis sp., CASA CC 101 their presence resulted in increased production of the PUFAs GLA, EPA and DHA. Significance and Impact of the Study This study shows that the addition of Fe and MJ to the culture media of Isochrysis sp., CASA CC 101 results in up-regulation of its genes Δ4Des, Δ6Des and Δ5Des, and improves the production of PUFA. Therefore, the addition of Fe and MJ to the culture medium is useful to increase the production of high-value PUFA in Isochrysis sp., CASA CC 101 and also to the other micro algal species.

Isochrysis is commercially available marine algae used for animal feed, human nutrient supplements, and biodiesel. The Isochrysis species is one of five genera of haptophytes that produces unique, long-chain lipids known as alkenones that are promising new ingredients for green cosmetics, personal care products and pharmaceutical delivery. However, there is a lack of toxicity data for alkenones in animals, thus limiting their use in humans. In this study, we performed acute oral, acute dermal, and repeated 28-day dermal toxicity studies, using female SAS Sprague Dawley Rats. Our behavioral studies indicated that the specific alkenones had no overt behavioural effects at oral doses up to 4000 mg/kg. In the acute and chronic dermal toxicity studies, the alkenones produced less irritation and did not significantly damage the skin based on the Draize skin reaction scale and trans-epidermal water loss readings compared to the positive control, 1% sodium lauryl sulfate. Overall, our results indicated that alkenones are safe in Sprague Dawley rats, suggesting that they could be used for both oral and dermal formulations, although additional studies will be required.

Upwelling is known to affect the ecology and life history of temperate nearshore organisms, and these effects are thought to be mediated by changes in temperature and food supply. However, little information is available for tropical systems. To understand how changes in the intensity of upwelling might impact marine invertebrates, we tested how factorial combinations of temperature, salinity, and phytoplankton availability affected growth and reproduction of a common intertidal snail, Crepidula cf. marginalis. We used temperatures typical of nonupwelling (29°C), moderate (26°C) and severe (23°C) upwelling, salinities typical of nonupwelling (30 ppt) and upwelling (34 ppt) and a good diet (Isochrysis) and a better diet (Isochrysis and Tetraselmis) as a proxy for increased productivity during upwelling. Overall, temperature and diet had consistent effects on body size, with better food and lower temperatures promoting larger size, as well as promoting shorter time to first reproduction. Diet had the largest effects on clutch size, with clutch size increasing with better diet. Temperature had the largest effect on offspring size and the frequency of discarded broods; offspring size decreased with increasing temperature and the frequency of discarded broods also decreased with increasing temperatures. We found no significant 3rd order interactions and few significant strong 2nd order interactions, which have often been found in similar experimental studies using stressful treatments. For this tropical slipper limpet, the effect of higher food and cooler temperatures during upwelling appears to be positive, promoting higher growth rates, larger clutch sizes, and larger offspring size suggesting that both factors likely play an important role underlying reproductive responses to upwelling. Climatic changes, like El Niño, which suppress upwelling in the Bay of Panama, appear likely to negatively impact this species., To understand how they interact to effect life histories, we raised tropical snails (Crepidula cf. marginalis) under a factorial combination of diet, temperature, and salinity. The results show that a combination of lower temperatures and higher food availability results in increased growth, larger broods, and larger hatching sizes. C. cf. marginalis, therefore, performs better under conditions similar to upwelling compared to those similar to nonupwelling conditions experienced in the Bay of Panama. This effect is largely mediated through the increased body size under higher food and cooler temperatures.

El presente estudio evaluó el uso de las microalgas Arthrospira sp., Chlorella sp., Isochrysis sp. y Nannochloropsis sp. como constituyentes parciales del alimento balanceado para tilapia del Nilo (Oreochromis niloticus) bajo condiciones de cultivo estático en un estudio de 53 días de duración. Un alimento balanceado comercial con contenido de proteína cruda de 45% se utilizó como dieta control, mismo que se molió finamente y se reconstituyó incorporando, a un nivel de inclusión de 25% de la dieta, las harinas de las cuatro especies de microalgas mencionadas. Se analizaron parámetros de producción de tilapia, incluyendo índices de crecimiento y supervivencia, mediante análisis de varianza. Los índices de crecimiento, tales como peso final, peso ganado y porcentaje de peso ganado de los peces alimentados con las microalgas Arthrospira sp. y Chlorella sp., así como la supervivencia, fueron similares a los de aquellos que recibieron la dieta control, mientras que el crecimiento de peces alimentados con las microalgas Isochrysis sp. y Nannochloropsis sp. fue inferior estadísticamente. Estos resultados indican que Arthrospira sp. y Chlorella sp. pueden ser incorporadas a un nivel de 25% del alimento balanceado sin afectar significativamente el crecimiento o la supervivencia de O. niloticus.ABSTRACTIn the present study, the use of the microalgae Arthrospira sp., Chlorella sp., Isochrysis sp., and Nannochloropsis sp., as partial constituents in diets for Nile tilapia (Oreochromis niloticus), was evaluated in static tanks in a 53-day study, with a commercial diet containing 45% crude protein as a control treatment. Then, we replaced 25% of this diet with meals derived from each of the four microalgae species. Analysis of variance was employed to evaluate fish growth performance. Fish fed the diets with the microalgae Arthrospira sp. and Chlorella sp. had growth performance comparable to that of fish fed the control diet, as evaluated by growth parameters, such as final weight, weight gain, and percent weight gain, among others. In contrast, growth of fish receiving the microalgae Isochrysis sp. and Nannochloropsis sp. was significantly lower. Results of the present study indicate that the use of 25% of Arthrospira sp. and Chlorella sp. meals incorporated into the diet of O. niloticus does not compromise fish development, although there seems to be an opportunity for a further increment of the replacement level.

The purpose of this work was to investigate the viability of a microalgae catalytic pyrolysis/hydrotreating plant to kerosene, diesel and gasoline using Aspen Plus. A series of 2000 dry tonne per day scenarios were simulated with the final goal of determine the price in USD per litre of the drop-in fuels produced and the economic feasibility of the technique at a large-scale. Different scenarios (mechanical, solar and thermal drying), microalgae (Nannochloropsis and Isochrysis) and catalysts (Li-LSX zeolite, Ni-Ce/Al2O3, Ni-Ce/ZrO2). For this work, a systematic design approach by Douglas was considered and the whole process was actualised with the Marshall and Swift Cost Index of 2016. The lowest minimum fuel selling price (1.418 $/L) was found for Isochrysis and Li-LSX-zeolite. Finally, the sensitivity analysis showed that the bio-oil yield was the most influent factor, leading to a variation of the fuel price between 1.158 $/L to 1.751 $/L assuming a 20% of variation. The techno-economic assessment and sensitivity analysis indicated that Isochrysis and Li-LSX-zeolites are promising for the production of drop-in fuels, but further research is required to further reduce the price of the feedstock production and drying to be competitive with lignocellulosic materials.

DEVELOPMENT of Nitzschia sp. AS SEDIMENT TEST ORGANISM. Sediment bioassay requires a test organism which suitable with the test material, for example sediment. However, benthic phytoplankton as the test organism has not been widely applied in Indonesia. Recently, bioassay test still uses phytoplankton which lives in water column such as Chaetoceros gracilis, Tetraselmis sp., Isochrysis sp., or uses another test organism like mussel, sea urchin larvae and amphipod. In addition, Nitszchia sp. is one of culture collection at Research Centre for Oceanography so it could be added value of culture collection. Therefore, this paper aims to describe the potential use of phytoplankton benthic, Nitzschia sp. as sediment test organism.

Unique algal lipids known as alkenones were evaluated as potential phase change materials (PCMs). Alkenones were isolated and purified from commercial Isochrysis algal biomass and their thermal properties evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Alkenone crystallinity appears to impact latent heat of fusion (ΔHfus), however both the ΔHfus and melting temperature (∼65 °C) of two different alkenone compositions obtained from separate commercial Isochrysis suppliers were nearly identical. Compared to a synthetic bis-fatty acid PCM, alkenones showed improved thermal stability by TGA and comparable ΔHfus (up to 275 J/g) by DSC. Overall the results demonstrate competitive properties for alkenones to other renewable and non-renewable PCMs such that alkenones represent a promising and potentially superior alternative for various ‘green’ PCM technologies.

Phytoplankton occupies a key trophic level in aquatic ecosystems. Chemical impacts on these primary producers can disrupt the integrity of an entire ecosystem. Two freshwater (Pseudokirchneriella subcapitata-Ps and Scenedesmus obliquus-S) and three marine (Phaeodactylum tricornutum-P, Isochrysis galbana-I, Tetraselmis suecica-T) microalgae species were exposed to dilutions of four chemicals: nanoparticles (n-TiO2, n-ZnO), amoxicillin (antibiotic), and white musk (personal care fragrance) to determine the half maximal effective concentration (EC50) after 72 h of exposure under standardized and controlled environmental conditions. Cell cultures were exposed to EC50 to determine sublethal effects (72 h) based on biochemical (chlorophylls a, b, c), molecular (changes in outer cell wall structure), and morphological alterations. We report for the first time EC50 values for nanoparticles in not standardized species (S, I and T) and for amoxicillin and white musk in all tested species. Standardized species (Ps and P) were less sensitive than non-standardized in some cases. Fourier-transformed infrared spectroscopy showed a marked spectral alteration (from 10.44% to 90.93%) of treated cultures compared to negative controls; however, principal component analysis disclosed no differences in molecular alteration between the five microalgae species or the two aquatic habitats considered. There was a significant decrease in chlorophylls content in all species exposed to EC50 compared to controls (Kruskal Wallis test; p < 0.05). There was a significant increase in cell-size (Mann–Whitney U test; p < 0.05) in I, P and T exposed to white musk and S exposed to amoxicillin. Findings highlight ecotoxicological risks from new generation pollutants for primary producers in aquatic ecosystems.

Marine and freshwater algae and their products are in growing demand worldwide because of their nutritional and functional properties. Microalgae (unicellular algae) will constitute one of the major foods of the future for nutritional and environmental reasons. They are sources of high-quality protein and bioactive molecules with potential application in the modern epidemics of obesity and diabetes. They may also contribute decisively to sustainability through carbon dioxide fixation and minimization of agricultural land use. This paper reviews current knowledge of the effects of consuming edible microalgae on the metabolic alterations known as metabolic syndrome (MS). These microalgae include Chlorella, Spirulina (Arthrospira) and Tetraselmis as well as Isochrysis and Nannochloropsis as candidates for human consumption. Chlorella biomass has shown antioxidant, antidiabetic, immunomodulatory, antihypertensive, and antihyperlipidemic effects in humans and other mammals. The components of microalgae reviewed suggest that they may be effective against MS at two levels: in the early stages, to work against the development of insulin resistance (IR), and later, when pancreatic -cell function is already compromised. The active components at both stages are antioxidant scavengers and anti-inflammatory lipid mediators such as carotenoids and -3 PUFAs (eicosapentaenoic acid/docosahexaenoic acid; EPA/DHA), prebiotic polysaccharides, phenolics, antihypertensive peptides, several pigments such as phycobilins and phycocyanin, and some vitamins, such as folate. As a source of high-quality protein, including an array of bioactive molecules with potential activity against the modern epidemics of obesity and diabetes, microalgae are proposed as excellent foods for the future. Moreover, their incorporation into the human diet would decisively contribute to a more sustainable world because of their roles in carbon dioxide fixation and reducing the use of land for agricultural purposes., This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (grant numbers AGL2017-83599-R).

To develop greener extraction alternatives for microalgae biomass, ultrasound assisted extraction (UAE) and pressurized liquid extraction (PLE) with different biobased solvents were investigated, demonstrating that both techniques are useful alternatives for algal lipid extraction. Specifically, Nannochloropsis gaditana lipids were extracted by UAE and PLE at different temperatures and extraction times with sustainable solvents like 2-Methyltetrahydrofuran (2-MeTHF) and its mixtures with ethanol and other alcohols. The best oil yields for both PLE and UAE of N. gaditana were achieved with the mixture of 2-MeTHF:ethanol (1:3), reaching yields of up to 16.3%, for UAE at 50 °C and up to 46.1% for PLE at 120 °C. Lipid composition of the extracts was analyzed by HPLC-ELSD and by GC-MS to determine lipid species and fatty acid profile, respectively. Different fractionation of lipid species was achieved with PLE and solvent mixtures of different polarity. Thus, for the extraction of glycolipids, ethanolic extracts contained higher amounts of glycolipids and EPA, probably due to the higher polarity of the solvent. The optimized method was applied to microalgae Isochrysis galbana and Tetraselmis chuii showing the potential of mixtures of biobased solvents like 2-methyl-THF and ethanol in different proportions to efficiently extract and fractionate lipids from microalgal biomass.

Microalgal biomass is a sustainable and valuable source of lipids with omega-3 fatty acids. The efficient extraction of lipids from microalgae requires fast and alternative extraction methods, frequently combined with biomass pre-treatment by different procedures. In this work, Pressurized liquid extraction (PLE) was optimized and compared with traditional lipid extraction methods, Folch and Bligh and Dyer, and with a new Ultrasound Assisted Extraction (UAE) method for lipids from microalgae Isochrysis galbana. To further optimize PLE and UAE, enzymatic pre-treatment of microalga Isochrysis galbana was studied with commercial enzymes Viscozyme and Celluclast. No significant differences were found for lipid yields among different extraction techniques used. However, advanced extraction techniques with or without pre-treatment are a green, fast, and toxic solvent free alternative to traditional techniques. Lipid composition of Isochrysis was determined by HPLC-ELSD and included neutral and polar lipids, showing that each fraction comprised different contents in omega-3 polyunsaturated fatty acids (PUFA). The highest polar lipids content was achieved with UAE (50 &deg, C and 15 min) and PLE (100 &deg, C) techniques. Moreover, the highest omega-3 PUFA (33.2%), eicosapentaenoic acid (EPA) (3.3%) and docosahexaenoic acid (DHA) (12.0%) contents were achieved with the advanced technique UAE, showing the optimized method as a practical alternative to produce valuable lipids for food and nutraceutical applications.

Microalgae are renewable and valuable natural sources of triacylglycerol (TAG) for nutritional application or specific purposes. The aim of this study was to evaluate the TAGs produced by twelve microalgae species for production of human milk fat substitutes (HMFs). The investigated species were Chlorella vulgaris (CV-15 and CV-395), Chlorella zofingiensis, Chlorella pyrenoidosa, Scenedesmus sp., Chlorococcum sp., Nitzschia laevis, Phaeodactylum tricornutum, Isochrysis sp., Isochrysis galbana, Nannochloropsis oceanica and Nannochloropsis salina. The total fatty acids (TFAs) contents of these species varied from 15.9 to 31.1%. TAG was the main lipid class (65.1–91.0%). Based on the evaluation model in view of the fatty acid composition and positional distribution of TAGs by GC–MS and 13C NMR, among the tested species, Isochrysis-derived TAGs mimicking human milk TAGs (HMTs) gave the highest G values (deducting score) that were close to that of lard. The G value (69.2) of Isochrysis sp. TAG was within the range of G value for local infant formulas; whereas, the G value (61.2) of I. galbana TAG was a bit lower than the lower limit of local infant formulas. Moreover, the melting and crystallization properties of TAGs from Isochrysis sp. and I. galbana were similar to those of HMTs. These results showed that Isochrysis TAGs could be promising candidates for HMFs feedstock.

The effects of mono- and bi-microalgal diets on shell length, organic tissue, and survival of Spondylus limbatus juveniles were tested in two separate feeding experiments. The first examined nine single species of microalgae: Chaetoceros gracilis, C. muelleri, Isochrysis aff. galbana (T-ISO), Tetraselmis chuii, T. maculata, Pavlova lutheri, Dunaliella salina, Rhodomonas sp., and Nannochloropsis sp. An extra treatment maintaining the juveniles in a long line culture was at Ayangue Bay, Province of Santa Elena, Ecuador. Single diets of P. lutheri, C. muelleri, and C. gracilis showed the best combined growth of survival performance in juveniles, and were therefore selected for the bi-algal diet experiment design with the inclusion of I. galbana T-ISO due to its recommended use in bivalve culture. A second experiment consisted in selecting the best three microalgae species that resulted from the first experiment and combined each other in binary treatments at 1:1 ratio. All bi-algal diets in combination with P. lutheri showed good result in growth (shell and biomass), yield, and survival. However, single P. lutheri mono-algal diet showed equal or better performance index than the other bi-algal combined diets, demonstrating the pertinence in using this microalga as food for S. limbatus juveniles.

The chlorophyll fluorescence parameters of Isochrysis. galbana at different nitrogen levels were determined by using chlorophyll fluorescence with the aim of better understanding the operative status of photosynthetic system II (PSII) and electron transport chain in oleaginous microalgae. In this experiment, the growth and photosynthetic efficiency were restricted in N-deprived I. galbana, which were mainly presented in significant decrease of cell numbers and chlorophyll content, the dramatic decline of Fv/Fm, P.I., ΦPSII and rETR, and commensurate increase of NPQ and Wk. The growth of algal cells gradually increased with rising nitrogen concentration, especially reached the top in N-1.76 mM L1 medium, but were inhibited in N-3.52 mM L1 medium. The results suggested that N-deprivation and N-deficiency could inhibit the growth and photosynthesis of I. galbana, but excessive nitrogen could also restrict the growth of algal cells. The nitrogen concentration plays an important role in the algal growth and photosynthesis.

In this exploratory study, eight types of microalgae from different phyla (Chlamydomonas reinhardtii, Chlorella species, Haematococcus pluvialis, Porphyridium purpureum, Porphyridium cruentum, Isochrysis species, Isochrysis galbana, and Pavlova lutheri) were tested for their antibacterial activities against eight target pathogenic bacterial strains. The agar well diffusion method and broth micro dilution assay were conducted to estimate the antibacterial activity. Microalgae cell-free supernatants, exopolysaccharides (EPS), water, and organic solvent extracts were used for inhibition analysis. EPS extracted from P. lutheri showed activity against Bacillus subtilis and Pseudomonas aeruginosa. Inhibition zone diameters of 14- 20 mm were recorded on agar plates, while the minimum inhibitory concentrations in the broth micro dilution assay were 0.39-25 mg ml-1. During this study, haptophyte microalgae, Isochrysis species, and P. lutheri extracts showed the highest activity against most of the tested pathogenic bacterial strains, while most of the extracts were active against the important foodborne pathogen P. aeruginosa. This study showed promising results regarding important microalgae phyla, which will further aid research related to extracts and exploitation of bioactive metabolic compounds in the food and pharmaceutical industries.

We report 1900-year long records of alknone concentration, C38/C37 ratio, and U 37 k , U 37 k ' and a newly-developed alkenone unsaturation index U 37 k ' ' -based temperatures in a sediment core retrieved from Kusai Lake in the northern Qinghai-Tibetan Plateau. The predominance of C37 and C38 alkenones with minor presence of C39 and C40 alkenones, and the absence of C38 methyl alkenones are indicative of alkneones produced by Isochrysis, which is consistent with the results of sedimentary haptophyte DNA analyses. The interval from 400 to 1200 AD is characterized by higher alkenone concentrations and C38/C37 ratios than the other intervals, which can be attributed to the predominant production of Isochrysis during the entire phytoplankton blooms. With the assistance of information on gene abundance, we attributed this phenomenon to drastic ecological changes in Kusai Lake around 1200 AD in response to climatic changes from warm and wet to cold and dry conditions, and resultant decreased riverine inflow but increased nutrient concentration. The U 37 k ' ' -based temperatures with U 37 k ' ' substituting U 37 k ' in a equation concluded based on studies on lakes from high latitude areas in Germany are the most reliable reconstructed summer surface water temperatures for Kusai Lake since they are close to the current summer monthly mean temperature of Wudaoliang Meteorological Station, approximately 50 km to the south of Kusai Lake, and exhibit variations that are generally in accordance with those of the 51-year moving average summer temperatures reconstructed from thicknesses of varve light layers in Kusai Lake sediments. Besides, variations showed by this U 37 k ' ' -based summer surface water temperatures are also generally consistent with those showed by reconstructed temperatures in China.

Microalgae could be of importance for future biodiesel production as an alternative for a third generation of biofuels. To select the most appropriate strain for biodiesel production, three microalgae species, namely Isochrysis sp., Nannochloropsis maritima and Tetraselmis sp., isolated from Tunisian coast, were biochemically characterized. Initially, gas chromatography analysis showed that Isochrysis sp. and N. maritima contained 5- and 10-fold total fatty acids, respectively, more than Tetraselmis sp. Then, the two microalgae Isochrysis sp. and N. maritima were subject to random mutagenesis using ultraviolet-C radiation. Subsequently, a total of 18 mutants were obtained from both species. The neutral lipid evaluation on said 18 mutants allowed the retention of only 7 to further fatty acid characterization. Finally, gas chromatography revealed that the mutant 5c Isochrysis sp. was characterized by a high level of saturated fatty acids (52.3%), higher amount of monounsaturated fatty acids (29.3%), lower level of polyunsaturated fatty acids (18.4%) and a significant 1.3-fold increase in its C16-C18 content compared to the wild-type strain, which would make it an interesting candidate for biofuel production.

The aim of this study is to produce new medium-long-medium structured triacylglycerols (MLM-STAGs) containing caprylic acid (CA) at the sn-1,3 positions, and long chain saturated fatty acids (LCSFAs) and bioactive fatty acids at the sn-2 position via two-step enzymatic process by Lipozyme TL-IM, using autotrophic microalgae (Isochrysis galbana) TAGs. In the first step, the ethanolysis of microalgae oil TAGs for 2-monoacylglycerols (2-MAGs) production are performed in the presence of water content of 5 wt% at ethanol/oil mole ratio of 24:1 with Lipozyme TL-IM at 25 °C for 12 h. In the larger-scale production of 2-MAGs, the 2-MAGs yield and the purity of the purified MAGs attained are 31.44-36.08 wt% and 91.57 mol%, respectively. In the second reaction, these 2-MAGs are esterified with caprylic acid (CA) in n-hexane system to synthesize almost pure MLM-STAGs with the recycled Lipozyme TL-IM under the optimized conditions. The final MLM-STAGs contain 64.28% CA and 13.35% ω-3 polyunsaturated fatty acids. The CA-LCSFAs-CA (43.01%) and novel CA-stearidonic acid (SDA, C18:4ω-3)-CA (23.88%) are the major MLM-STAGs present. In all, Isochrysis galbana-derived oil containing SDA is a promising source for producing high-value microalgal bioproducts by two-step enzymatic process in a cost-effective manner.

Brachionus plicatilis is used to feed fish and crustacean larvae in the aquaculture industry. It is well established that the type of microalgae may influence rotifer production. This experiment was conducted to determine the effect of five different locally available microalgae species at Fisheries Research Institute (FRI), Kampung Pulau Sayak, Kedah, Malaysia on the instantaneous growth rate (μ) of rotifer. Nannochloris sp., Tetraselmis sp., Isochrysis sp., Chlorella sp., and Nannochloropsis sp. were used as feed at different algae densities (0.1, 0.3, 0.7 and 1.5 × 106 cells/ml) and culture volumes (20, 70 and 210 ml). At algae densities ranging from 0.3 to 1.5 × 106 cells/ml, an average μ value of more than 0.90 per day were recorded for all algae species. However, at density of 0.1 × 106 cells/ml, only Tetraselmis sp. resulted in the significantly highest μ value compared with others (p < 0.05). In terms of volume, smaller culture volume of Tetraselmis sp. (20 ml) showed significantly higher μ compared with higher volume (70 and 210 ml cultures).

Microalgae as feedstock of bioenergy, mainly biodiesel, is receiving an increased attention from scientific and industrial point of view. The selection of promising strains and optimization of the production process are essential keys to develop an economically viable project. In this context, fifty-seven strains of marine microalgae have been isolated from the Moroccan Atlantic and Mediterranean coasts. The selection of most promising strains was based on biomass productivity, lipid content and fatty acids profile. Nannochloropsis gaditana (24), Chlorella sp (67), Dunaliella tertiolecta (29) , Isochrysis sp (77), Phaeodactylium tricornutum (23) and Chaetoceros sp (63) showed the best growth rate, whereas lipid content was highest in Navicula sp (up to 63%) and Tetraselmis sp (up to 56%), Dunaliella sp (up to 50%), Nannochloropsis sp (up to.60%) and Chaetoceros sp (up to 56%). Fatty Acids Methyl Ester profiles were analyzed and most strains studied showed a high rate of PUFA’s mainly those belonging of Dunaliella , Tetraselmis , Isochrysis and Nannochlorpsis genuis. For Bacillariophyceae, despite their high content in lipids, their FAME profile was rich in PUFA’s which affects the quality of biodiesel. This study describes the microalgae screening process and demonstrates that Nannochloropsis sp, Dunaliella tertiolecta, Isochrysis sp and Tetraselmis sp are among promising species as biodiesel feedstock.

The geoduck clam, Panopea generosa, is a species from the west coast of Baja California, Mexico, and the optimization of seed production systems is still a limiting factor for its aquaculture. In this study, a flow‐through culture system was designed and tested in P. generosa larvae. Survival and growth was compared in triplicate 45‐L fiberglass tanks using three larval densities (5, 10 and 15 larvae/ml). A head tank kept constant the water inflow, with a daily renewal rate of 1.8× tank volume. The food (Isochrysis spp.) was dosed according to the ingestion rate of larvae and the dilution rate. Survival decreased linearly during the first 10 days and reached asymptotic values of ca. 20% (15 larvae/ml) and 50% (densities of 5 and 10 larvae/ml) afterwards. Mean shell length at the end of the experiment (243 ± 1.8 to 270 ± 0.7 μm) was not statistically different among treatments, even though a trend towards higher gross growth rate was observed in the treatment with the lowest density (9.5 μm/day) relative to the rest of the treatments (8.5 μm/day). It is concluded that P. generosa larvae can be successfully grown in flow‐through systems at maximum densities of 10 larvae/ml without significantly affecting their survival and growth rates. The system design was reliable, kept a constant water flow with reduced maintenance, and may represent an important option in the laboratory for increasing the stocking density of Panopea species during the larval phase.

The importance of polyunsaturated fatty acid (PUFA) in microalgae was widely reported. In this study, six isolated microalgae from Teluk Aling, Penang National Park were screened for PUFA contents. Isochrysis maritima showed the best polyunsaturated fatty acids essential for aquaculture species compared to other microalgal species tested. This species is a good choice as aquaculture feed due to its small size (3-7 μm), which is appropriate size for ingestion. The maximum specific growth rate of this species was also high (0.52-0.82 days-1) and comparable with many recognised aquaculture microalgae. On the other hand, this species was also able to be cultivated successfully in big volume (1000 L culture medium) with open hatchery condition, which will optimise the production cost. Low ratio of omega-6 to omega-3 essential fatty acids (EFA) recorded in I. maritima at any growth phases (0.32-0.45) also indicate optimal values for feeding.

Polyunsaturated long-chain alkenones are a unique class of lipids biosynthesized in significant quantities (up to 20% of cell carbon) by several algae including the industrially grown marine microalgae Isochrysis. Alkenone structures are characterized by a long linear carbon chain (35–40 carbons) with one to four trans double bonds and terminating in a methyl or ethyl ketone. Alkenones were extracted and isolated from commercially obtained Isochrysis biomass and then subjected to cross-metathesis (CM) with methyl acrylate or acrylic acid using the Hoveyda–Grubbs metathesis initiator. Within 1 h at room temperature alkenones were consumed; however, complete fragmentation (i.e., conversion to the smallest subunits by double bond cleavage) required up to 16 h. Analysis of the reaction mixture by gas chromatography and comprehensive two-dimensional gas chromatography revealed a predictable product mixture consisting primarily of long-chain (mostly C17) acids (or methyl esters from CM with methyl acrylate) and diacids (or diesters), along with smaller amounts (~5%) of the honey bee “queen substance” (E)-9-oxo-decenoic acid. Together, these compounds comprise a diverse mixture of valuable chemicals that includes surfactants, monomers, and an agriculturally relevant bee pheromone.

Promising biological objects containing the maximum amounts of lipids were selected for further study based on an analysis of published studies on the quantitative and qualitative composition of lipids accumulating in microalgae. The genera Navicula and Isochrysis were found to be most optimal for liquid biofuel production because they contained the maximum percentage of triacylglycerides in the total lipids. Freshwater species of these microalgae genera can be considered most suitable for cultivation in CFD bioreactors as a primary product of biofuel production. Innovative methods using vortex devices are proposed for removing the algal oil.

Biosynthesis of metal nanoparticles has received a remarkable attention due to their eco-friendly and potential applications in pharmaceutical and medical fields. The searches for natural alternatives to replace biosynthetic nanoparticles have resulted in extensive studies of microalgal derived metal nanoparticles. Since there are very limited reports on Isochrysissp. in synthesising metal nanoparticles, a novel initiative was taken to induce an environmentally friendly and low cost technique to biosynthesise the silver nanoparticles (AgNPs) using marine microalgae, Isochrysis sp. Further, the synthesised silver nanoparticles were screened against human pathogen for antimicrobial effects. The characterisation of nanoparticles were confirmed by UV-visible spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), and X-ray powder diffraction (XRD). The results obtained from characterisations indicate that the AgNPs have an almost spherical shape with a various size of 98.1 to 193 nm. The synthesised nanoparticles exhibited outstanding antioxidant and antimicrobial activities.

Information on the nutritional requirements and preferred diets of sea cucumber juveniles is extremely limited and this has hindered development of hatchery culture methods. This study assessed ingestion, cell wall digestion and relative nutritional values of two live micro-algae (Isochrysis aff. galbana (TISO) and Chaetoceros muelleri) and six concentrated micro-algae products (Instant Algae®, Reed Mariculture Inc.) for early juveniles of sandfish, Holothuria scabra. Seven of the eight micro-algae tested were ingested by juveniles with the exception of live TISO. Faeces excretion times varied between ingested diets that passed through the juvenile gut in less than 1 h. The cell walls of five of the eight micro-algae tested were partially or mostly digested (Chaetoceros muelleri, TW1200®, Palova 1800®, Isochrysis 1800® and Shellfish 1800®), while the cell walls of Tetraselmis 3600® and 3H 1800® remained intact. Juvenile growth rates were significantly different between diet treatments over the duration of a 14 day growth trial. Mean (± SE) length of early juveniles at the end of the growth trial was highest for those fed live C. muelleri (4.10 ± 0.03 mm) followed by TW 1200® (3.49 ± 0.05 mm). Juvenile survival did not differ significantly between diet treatments and was highest for those fed C. muelleri (79.33 ± 6.11%) followed by TW1200® (78.33 ± 1.20%). Pearson's correlation tests were used to identify key correlations between the levels of specific nutrients and juvenile performance (growth and survival). A significant positive correlation between growth and dietary protein content (P < 0.05), and a highly significant positive correlation between growth and dietary EPA:DHA ratio (P < 0.01) provide new information to inform diet selection for juvenile sandfish that will help improve juvenile performance and support improved hatchery production. Use of commercially available micro-algae concentrates as a replacement for live micro-algae in sandfish hatcheries supports development of cheaper, simpler post settlement rearing protocols for this species.

Knowledge of ingestion and digestion of micro-algae by bivalve larvae is critical for provision of appropriate larval nutrition supporting maximal growth and survival. However, little is known about the ingestion and digestion of micro-algae by giant clam larvae. This study determined the rates of ingestion and digestion of commercially available micro-algae concentrates by Tridacna noae larvae of different ages using epifluorescence microscopy. The micro-algae used were Isochrysis sp. (Isochrysis 1800®), Pavlova sp. (Pavlova 1800®), Tetraselmis sp. (Tetraselmis 3600®) and Thalassiosira weissflogii (TW 1200®). None of the four micro-algal concentrates were ingested by T. noae larvae at 24 h post-fertilisation, but all were ingested at 48 h and 72 h post-fertilisation, at different frequencies. At 48 h post-fertilisation, Isochrysis sp. and Pavlova sp. were ingested by 77% and 70% of veligers, respectively, while T. weissflogii and Tetraselmis sp. were ingested by 10% and 30% of veligers, respectively. Similar rates of ingestion were observed for each micro-alga by larvae at 72 h post-fertilisation. Larvae capable of ingesting micro-algae concentrates were significantly larger than those that were empty and the minimum antero-posterior shell length of T. noae larvae capable of ingesting Pavlova sp. and Isochrysis sp. was 141 μm and 132 μm, respectively. Digestion of micro-algae by 48 h-veligers was observed 2 h after the start of feeding in 26.1% and 14.3% of larvae that had ingested Isochrysis sp. and Pavlova sp., respectively, but digestion of Tetraselmis sp. and T. weissflogii was not observed until 4 h and 8 h after the start of feeding, respectively. Complete digestion of Pavlova sp. and Isochrysis sp. took up to 12 h in larvae at both 48 h and 72 h post-fertilisation. Our results provide a basis for developing a more nutritionally informed approach to hatchery culture of T. noae.

The fan mussel, Pinna nobilis, is an endemic Mediterranean species, whose populations have been seriously affected by infectious diseases. The effect of diet composition on growth and survival rates, and on nutritional metrics including ingestion and absorption rates, together with food preferences were investigated in 48 juveniles. Individuals were initially acclimated to conditions of captivity with a mixed diet of three species of microalgae cultured in situ and riverine sediment. Then, they were changed to different diets based on combinations of commercial phytoplankton gels and riverine sediments except for a control group that was maintained under the acclimation conditions. Diet A consisted of Tetraselmis chuii; diet B on a 2 species mix of T. chuii and Isochrysis aff. galbana (T-ISO), diet C on a 3 species mix T. chuii, T-ISO and Phaeodactylum tricornatum, diet D on riverine sediment without microalgae, and diet E on T. chuii and riverine sediment. Individuals under experimental diets were fed ad libitum once per day and the water with food excess replaced before the next ration. The control diet showed the highest survival and growth (50% vs. 2.5% survival and ca. 6 mm vs.

This paper investigates the use of Li-LSX-zeolite catalyst over three regeneration cycles in presence of non-treated and acid pre-treated Isochrysis sp. microalgae. The spent and regenerated catalysts were characterised by surface analysis, elemental analysis (EA), SEM-EDS, and XRD to correlate their properties with the bio-oil yield and quality. The acid pre-treatment removed alkali metals, reducing gas yield in favour of bio-oil, but, at the same time, led to catalyst deactivation by fouling. Differently, the non-treated microalgae resulted in a bio-oil enriched in C and H and depleted in O, compared to the pre-treated ones, denoting higher deoxygenation activity. After 3 pyrolysis/regeneration cycles, the analyses suggest that there are no major changes on catalyst using non-treated microalgae. Regeneration at 700 °C has been shown to be able to remove most of the coke without damaging the Li-LSX zeolite structure. In summary, Li-LSX zeolite was effective in maintaining deoxygenation activity over three cycles in the pyrolysis of non-treated Isochrysis microalgae, while the algae pre-treatment with sulphuric acid was detrimental on the catalyst activity.

The elemental stoichiometry, growth and biochemical composition of Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. were studied in batch cultures against different nitrogen and sulfur molar ratios (N:S) imposed in their surroundings. In N. gaditana, treatments with low N:S lead to an increase in carbon:sulfur (C:S) and N:S molar ratios up to 95 and 81%, respectively. This was reflected in lipid and protein contents which increased up to 67 and 55%, respectively. Moreover, polyunsaturated fatty acids, as well as its precursors, increased in low N/S treatments. In R. marina, the treatments applied promptly the decrease of both C:S and N:S ratios to 70 and 68%, respectively. Nevertheless, eicosapentaenoic:arachidonic acid ratio increased with N:S treatments by three and a half fold. In Isochrysis sp., the elemental stoichiometry was constrained against treatments until the highest sulfur input. Overall, sulfur supply highlighted microalgae taxonomic differences and suggested that biochemical control is required, even in nutrient replete conditions, to fully exploit their potential as added value biomachineries.

Microalgae represent a putative solution to decontaminate metal polluted aquatic sites (phycoremediation). Seven different freshwater and seawater microalgal strains (Nannochloropsis sp., Dunaliella sp., Phaeodactylum sp., Chlorella sp., Isochrysis sp., Euglena sp. and Chlorogonium sp.) were exposed to five metals (Cu, Zn, As (III), Fe and Ni) at three concentrations each, simulating highly polluted sites. The experiment was conducted for a week; the survival ability of each strain and the photosynthetic pigments content (chlorophyll a, b and carotenoids) were evaluated, together with the Optical Density of each culture, pH, growth rate and biomass. Results highlighted different resistance patterns towards metals characterizing each algal strain, and the tolerance of all the microalgal strains towards arsenite. For the first time, the metal resistance pattern of Chlorogonium sp. was evaluated. Finally, our Euglena sp. and Dunaliella sp. strains were considered among the most promising organisms for phycoremediation of freshwater and seawater polluted sites respectively.

Aquaculture, the fastest growing food sector, is expected to expand to produce an additional 30 million metric tons of fish by 2030, thus filling the gap in supplies of seafood for humans. Salmonids aquaculture exploits the vast majority of fishmeal and fish oil rendered from ocean-dwelling forage fish. Most forage fish diverted to these commodities are human-food grade, and all are primary prey for marine predators. Rising costs, price volatility, and environmental sustainability concerns of using these commodities for aquaculture feed are driving the global search for alternatives, including marine microalgae originating from the base of marine food webs but produced in culture. We report the first evaluation of two marine microalgae, 'Nannochloropsis' sp. and 'Isochrysis' sp., for their potential to fully replace fishmeal and fish oil in diets of rainbow trout ('Oncorhynchus mykiss'), an important model for all salmonid aquaculture. We conducted a digestibility experiment with dried whole cells of 'Nannochloropsis' sp. and 'Isochrysis' sp., followed by a growth experiment using feeds with different combinations of 'Nannochloropsis' sp., 'Isochrysis' sp., and 'Schizochytrium' sp. We found that digestibilities of crude protein, crude lipid, amino acids, fatty acids, omega 3 polyunsaturated fatty acids (n3 PUFA), docosahexaenoic acid (DHA), n6 (omega 6) PUFA in 'Isochrysis' sp. were significantly higher than those in 'Nannochloropsis' sp. Digestibility results suggest that for rainbow trout diets 'Isochrysis' sp. is a better substitute for fishmeal and fish oil than Nannochloropsis sp. The lower feed intake by fish fed diets combining multiple microalgae, compared to fish fed the reference diet, was a primary cause of the growth retardation. In trout fillets, we detected an equal amount of DHA in fish fed fish-free diet and reference diet. This study suggests that 'Isochrysis' sp. and 'Schizochytrium' sp. are good candidates for DHA supplementation in trout diet formulations.

Energy is becoming one of the most expensive production inputs nowadays. Energy reserves are starting to run out and their polluting nature has become undeniable. Therefore, there is an urgent necessity for renewable energies. One of these energy sources is algae, which are seen as promising for biofuel production. Algae can be cultured in non-agricultural land, high photosynthetic activity, harvested throughout the year high biomass production. High lipid from algae is possible by reducing some elements of growth conditions from the nutrient medium. In this study, Isochrysis affinis galbana species were cultured in two reactors; flat panel photobioreactors with different light paths (1, 3, 5, 7 and 10 cm) and tubular photobioreactors, with 50% nitrogen reduction and 20% inoculation densities. Biomass, lipid and protein ratios were determined. The highest lipid content of 33.13% was obtained from I. aff. galbana with 12.11% protein in flat panel photobioreactors with 50% nitrogen reduction and 10 cm light path, and a 0.991 g L-1 biomass rate was obtained. The highest optical density was found in the 10 cm light path flat panel photobioreactor with a 50% nitrogen reduction.

The discovery of non-fish sources of polyunsaturated fatty acids (PUFAs) is of great biotechnological importance. Although various oleaginous microalgae and fungi are able of accumulating storage lipids (single cell oils – SCOs) containing PUFAs, the industrial applications utilizing these organisms are rather limited due to the high-fermentation cost. However, combining SCO production with other biotechnological applications, including waste and by-product valorization, can overcome this difficulty. In the current review, we present the major sources of fungi (i.e. members of Mucoromycota, fungoid-like Thraustochytrids and genetically modified strains of Yarrowia lipolytica) and microalgae (e.g. Isochrysis, NannochloropsisandTetraselmis) that have come recently to the forefront due to their ability to produce PUFAs. Approaches adopted in order to increase PUFA productivity and the potential of using various residues, such as agro-industrial, food and aquaculture wastes as fermentation substrates for SCO production have been considered and discussed. We concluded that several organic residues can be utilized as feedstock in the SCO production increasing the competitiveness of oleaginous organisms against conventional PUFA producers.

Marine microalgae such as Isochrysis sp. and Pavlova sp. are the predominant source of polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA, 20:5n–3) and docosahexaenoic acid (DHA, 22:6n–3). EPA biosynthesis pathway is predominant in lower eukaryotes, and its biosynthetic gene expressions are not well established. Till date, the C18 elongation enzymes for EPA biosynthesis have not been identified from lower eukaryote. In the present study, we describe the identification of two microalgal genes Δ6-elongase and Δ5-desaturase involved for EPA biosynthesis. By PCR-based technique, a novel elongase gene (Δ6Elo-Iso) was isolated from Isochrysis sp., and 654 bp of full-length sequence was identified, which catalysed the conversion of SDA into ETr in E. coli. The identified gene displayed unique substrate specificity for both n-3 and n-6 C18-substrates for Δ6-elongation, with no activity towards Δ9-elongase. In addition, a novel Δ5-desaturase gene (Δ5Des-Pav) was isolated from Pavlova sp. and found an ORF of 1149 bp in length, which was capable of converting ETr into EPA in omega-3 pathway. For the first time, the heterologous expressions of two novel microalgal genes were successfully expressed in Escherichia coli. EPA production from E. coli is being considered as an alternative and economic source for industrial and pharmaceutical sectors.

Marine microalgae and their extracts, in recent years, have found applications, including use as biofuels, medicines and food. Recently, alkenones, a unique chain of long-chain lipids, extracted from Isochrysis microalgae, has emerged as a useful by product. This is the first review that summarizes the potential applications and limitations of alkenones use in paleoclimatology, biofuel, personal care industry and therapeutics.

The Great Plains of North America often experience prolonged droughts that have major economic and environmental impacts. Temperature reconstructions are thus crucial to help decipher the mechanisms responsible for drought occurrences. Long‐chain alkenones (LCAs), lipids produced by three major phylogenetic groups (Groups I, II, and III) of haptophyte algae within the order Isochrysidales, are increasingly used for temperature reconstructions in lacustrine settings. However, to select the most appropriate calibration of the LCA‐based temperature proxy, it is first essential to identify the LCA‐producing haptophyte species present. Here we used next‐generation sequencing to target the 18S rRNA haptophyte gene from sediments with distinct LCA profiles to identify the LCA‐producer(s) from five Canadian prairie lakes. In total, 374 operational taxonomic units (OTUs) were identified across the studied samples, of which 234 fell within the Phylum Haptophyta. Among the most abundant OTUs, three were characterized as LCA‐producers, one falling within the Group I haptophytes and two within the Group II haptophytes. The OTU from Group I haptophytes was associated with a single, highly specific LCA profile, whereas Group II OTUs showed higher variability in LCA distributions. Our study revealed that most of the LCA‐producing OTUs thriving in the Canadian lakes are included within the genus Isochrysis, which helps guide selection of the most appropriate calibration for down‐core temperature reconstructions. Our findings also suggest that the temperature dependency is likely consistent within different taxa from Group I and Group II haptophytes, but that other environmental parameters may influence the accuracy of the calibration.

This work was the first time to establish a green pressurized liquid extraction (PLE) process to extract microalgal lipids from Isochrysis biomass. PLE with ethanol exhibited superior lipid extraction performance in comparison to Soxhlet and Folch methods and PLE with n-hexane. To reduce the cost in ethanol utilization, ethanol concentration was optimized and found that PLE with 90% ethanol concentration obtained the highest lipid extraction efficiency (41.5 wt%) and total fatty acids (TFAs) recovery value (92.17 wt%) using Isochrysis sp. biomass. Results about lipid class detected by TLC-FID technique showed that ethanol concentration distinctly affected the content of lipidic class during lipid extraction by PLE. Similarly, the process with 90% ethanol concentration achieved over 90 wt% of TFAs recovery values with three different Isochrysis species. Overall, PLE process mediated with ethanol was a promising approach to extract Isochrysis-derived lipids from sustainable microalgal biomass for food application.

Kegiatan pembenihan lobster masih dikembangkan di Indonesia. Sintasan yang rendah dan pakan yang sesuai masih menjadi masalah utama dalam kegiatan pembenihan lobster. Artemia sebagai pakan utama diduga belum mencukupi kebutuhan nutrisi larva lobster. Upaya pemberian bahan pengaya sebagai alternatif untuk meningkatkan nutrisi diharapkan dapat meningkatkan sintasan larva lobster. Pemberian bahan pengaya yang mengandung asam lemak dokosa heksanoid acid (DHA) ke Artemia dianggap penting bagi pertumbuhan dan sintasan pada krustasea. Tujuan penelitian ini untuk mengetahui performa larva lobster berdasarkan tingkat sintasan maupun perkembangan larva dengan pemberian pakan artemia yang diperkaya dengan DHA. Perlakuan yang diberikan meliputi Artemia yang baru menetas (A), Artemia yang diperkaya dengan plankton Isochrysis galbana strain Tahiti konsentrasi (1-1,5 x 106 sel/mL) (B), DHA selco dosis 0,6 g/L (C), dan Artemia inkubasi 18 jam tanpa pengayaan (D). Pemeliharaan larva dilakukan pada bak 100 L dengan sistem air stagnan. Perkembangan larva yang mampu dicapai pada semua perlakuan adalah stadia-IIIa. Pemberian Artemia yang diperkaya dengan DHA selco menunjukkan hasil sintasan yang lebih baik pada pemeliharaan enam hari pertama namun tidak memberikan pengaruh yang signifikan. Pada masa pemeliharaan sampai 20 hari terjadi penurunan sintasan (SR) mencapai hanya 1%. Hal ini disebabkan adanya bakteri dan protozoa seperti jenis protozoa Zoothamnium sp. dan bakteri berfilamen teramati menempel pada tubuh larva sehingga mengganggu pergerakan dan kemampuan larva dalam menangkap mangsa. Berdasarkan penelitian ini maka penggunaan pakan Artemia yang diperkaya DHA Selco dapat menjadi alternatif pakan larva lobster namun tetap diperlukan kontrol kualitas air yang baik.Efforts to culture spiny lobster, Panulirus homarus larvae are still being developed in Indonesia. One of the main challenges in lobster hatcheries is to find an appropriate feed and improving larval survival. Artemia has been used as the main feed and considered to have insufficient nutritional ingredient for lobster larvae. Enrichment of feed to improve its nutrient contents is expected to increase the larval survival. DHA-enriched feed is considered essential for growth and survival of crustaceans. The aim of this study was to determine the survival and development of larvae fed with DHA-enriched Artemia. The treatments consisted of newly hatched Artemia (A), enriched Artemia with phytoplankton, Isochrysis galbana strain Tahiti at a density of 1-1.5 x 106 cells/mL (B), enriched Artemia with DHA selco at a dose of 0.6 g/L (C), and Artemia incubated for 18 hours without DHA enrichment (D). Each Artemia enrichment was performed for 18 hours. Larval rearing was carried out in a 00 L tank with static water system. The achieved larval developmental stage in all treatments was stage-IIIa. Administration of enriched Artemia with DHA selco showed a better larval survival during the first six days of larval rearing. But, it did not give any significant effect. The survival was then decreased to only 1% on day-20. This was due to the presence of bacteria and protozoa which decreased water quality. Protozoa Zoothamnium sp. and filamentous bacteria were observed attaching to the body of the larvae, disrupting the movement and ability of larvae in capturing prey. Based on this research, the use of Artemia enriched with DHA selco as an alternative for lobster larvae feed, but better water quality control is still needed.

The rich nutritional profile of microalgae biomass has made it a promising clean label food ingredient that has the potential to fortify incorporated food with simultaneous modification of the structural properties. This work investigated the effect of high pressure homogenization (HPH) at 300, 600, and 900 bar on the microstructural and rheological properties of four microalgal suspensions, namely, Arthospira platensis, Isochrysis sp., Nannochloropsis sp., and Tetraselmis sp. HPH treatment resulted in the disintegration of microalgal cells, which altered the cell morphology, particle size, and rheological properties. A. platensis, Isochrysis sp., and Tetraselmis sp. showed a linear HPH intensity-dependent cell disintegration as evidenced by an increase in viscosity of the suspensions. While A. platensis exhibited the most pronounced effect of HPH treatment, Nannochloropsis sp. showed a minimal response that was attributable to its strong cell walls. The significant interspecies differences in the colloidal properties of the HPH-treated microagal suspensions coincided with the proportion of various nutrients where the fluctuation of lipids (between 8% and 17%) and proteins (between 10% and 57%) affected hydrophilic/hydrophobic interactions between the macromolecules. The findings demonstrate that HPH can be used to tailor microalgae biomass for specific food applications as potential structuring ingredients.

Microalgal cultivation in wastewater is a multi-strategic approach for the effective treatment of effluents and sustainable generation of bioenergy as well as byproducts. Rapid growth rate, efficient carbon capturing technique and wide range of tolerance are the key attributes which makes microalgae an outstanding source of renewable energy. The present work involves the comparison of remediation potential of marine diatom Chaetoceros and haptophyte Isochrysis when cultivated on wastewater optimized nutrient media. The results show that both the strains can effectively remediate total nitrite up to 0.63% by T2 of Chaetoceros and 5.57% by T3 of Isochrysis, Remediation of total phosphorous 83–84% by T3 and T4 of Chaetoceros and almost 84–94% by T4 and T5 of Isochrysis. The reduction in chemical oxygen demand was most effective in T3 and T4 of Chaetoceros (146–157 mg L−1) and from T4 to T6 of Isochrysis (89–93%). Further, both the rate of lipid and biomass productivity was recorded highest in T6 of Chaetoceros (0.05 and 2.79 g L−1d−1), and in T4 and T5 of Isochrysis (0.02–0.022 and 1.11–1.27 g L−1d−1), respectively. Concomitantly, triggered productivity of total PUFA from 33.5% to 71.6% in case of Chaetoceros and from 20% to 63.4% in Isochrysis highlights the scope and effectiveness of the optimized nutrient media for cultivation and sustenance of either strain in enumerating their potential as a sustainable feed and source of biofuels.

The growth and biochemical composition of photoautotrophic and heterotrophic Isochrysis maritima in 50 L of Walne’s medium were compared. Heterotrophic I. maritima fed with 0.02 M glucose had a 4.6-fold higher maximum cell density (38.17 ± 0.23 × 106 cells mL−1) than photoautotrophic cells (8.29 ± 0.70 × 106 cells mL−1). The carbohydrate content was slightly higher in heterotrophic cells at all growth stages (mid-exponential, 40.8%; early stationary, 48.3%; and late stationary, 47.6%), but there was no significant effect on the protein content under either trophic condition. The total saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) were higher under heterotrophic conditions than those under photoautotrophic conditions. However, because omega-3 PUFAs are the most essential element in feed nutrition, low results for eicosapentaenoic acid (EPA) (0.28 ± 0.06%) and docosahexaenoic acid (DHA) (3.22 ± 0.26%) in the heterotrophic cells compared to the photoautotrophic cells (EPA: 0.44 ± 0.11%; DHA: 8.58 ± 0.73%) plus a low omega-3/6 PUFAs ratio (heterotrophic: 0.16–0.47; photoautotrophic: 2.60–2.88) and high value of (SFA + MUFA)/PUFA (heterotrophic: 5.50–6.81; photoautotrophic: 2.64–3.60) showed that this species is not suitable for aquaculture feed when cultivated under heterotrophic conditions.

Although the research of microalgae pyrolysis has been conducted for many years, there is a lack of investigations on energy efficiency and life cycle assessment. In this study, we investigated the biocrude yield and energy efficiency of direct pyrolysis, microalgae residue pyrolysis after lipid extraction (indirect pyrolysis), and different microalgae co-pyrolysis. This research also investigated the life cycle assessment of the three different pyrolysis pathways. A system boundary of Well-to-Wake (WTWa) was defined and included sub-process models, such as feedstock production, fuel production and pump-to-wheels (PTW) stages. The pathway of Isochrysis indirect pyrolysis shows the best performance in the mass ratio and energy ratio, produces the most kerosene component precursor, has the lowest WTWa total energy input, fossil fuel consumption and greenhouse gas emissions, and resultes in the best energy efficiency. All the evidence indicates that Isochrysis R2 pathway is a potential and optimal pyrolysis pathway to liquid biofuels. The mass ratio of pyrolysis biocrude is shown to be the decisive factor for different microalgae species. The sensitivity analysis results also indicates that the life cycle indicators are particularly sensitive to the mass ratio of pyrolysis biocrude for microalgae-based hydrotreated pyrolysis aviation fuel.

The aim of this work is to compare the life cycle assessments of low-N and normal culture conditions for a balance between the lipid content and specific productivity. In order to achieve the potential contribution of lipid content to the life cycle assessment, this study established relationships between lipid content (nitrogen effect) and specific productivity based on three microalgae strains including Chlorella , Isochrysis and Nannochloropsis . For microalgae-based aviation fuel, the effects of the lipid content on fossil fuel consumption and greenhouse gas (GHG) emissions are similar. The fossil fuel consumption (0.32–0.68 MJ·MJ −1 MBAF) and GHG emissions (17.23–51.04 g CO 2 e·MJ −1 MBAF) increase (59.70–192.22%) with the increased lipid content. The total energy input decreases (2.13–3.08 MJ·MJ −1 MBAF, 14.91–27.95%) with the increased lipid content. The LCA indicators increased (0–47.10%) with the decreased nitrogen recovery efficiency (75–50%).