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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.

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.

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).

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.

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.

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 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.

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 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.

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.

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.

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.

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%).

Previously, it has been observed that lipolysis occurring during (even short term) wet storage of microalgal biomass causes high free fatty acid (FFA) concentrations in the biomass. These FFA have a negative impact for different applications of microalgal lipids, e.g. downstream processing problems in biodiesel production, off-flavors and loss of nutritional value for food applications. However, it is not clear which factors influence lipolysis in microalgal biomass and which lipid class are more susceptible to lipolysis. In this study, wet biomass of T-Isochrysis lutea was stored at 20°C, 4°C and -20°C during 3 weeks. The extent of lipolysis was followed by analyzing the lipid classes distribution by ultrahigh-performance liquid chromatography−accurate mass mass spectrometry (UHPLC-amMS) and the FFA content. It was observed that FFA were formed very rapidly during post-harvest storage of wet biomass at 20°C and 4°C, the rate of this process being faster at 20°C than at 4°C, while almost no lipolysis was observed at -20°C. However, the FFA content levelled off after several days of storage because FFA reacted with alcohols to form fatty acyl esters. publisher: Elsevier articletitle: Lipolysis in T-Isochrysis lutea during wet storage at different temperatures journaltitle: Algal Research articlelink: http://dx.doi.org/10.1016/j.algal.2016.07.003 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved. ispartof: Algal Research vol:18 pages:281-287 status: published

In this study, the fresh water green microalga Scenedesmus dimorphus and the marine golden Isochrysis aff. galbana were compared at the laboratory scale for their potential in biodiesel production. For this purpose, the microalgal strains were grown over five days under the Bristol and Erdschreiber's media conditions. The cultures were supplied with 1.5% carbon dioxide (CO2) and 16:8 light to dark cycle at fixed temperature. The research performed contained the following stages: 1) Growth monitoring (analysis of growth rate), 2) Microalgae harvesting (lab-scale lipid extraction), 3) Biodiesel production and 4) Determination of biodiesel quantity and quality. The results show that the total lipids (% dry weight biomass) from Scenedesmus dimorphus and Isochrysis aff. galbana cultures were found to be 15.87 and 42.65%, respectively. The obtained yields of the transesterification reactions were 87.4% (Scenedesmus dimorphus) and 94.6% (Isochrysis aff galbana). The methyl esters of Isochrysis aff. galbana contained higher percentage of saturated fatty acids than Scenedesmus dimorphus and its fatty acid composition improved the basic fuel properties. The overall finding of the study suggested that Isochrysis aff. galbana can be considered as more viable source for biodiesel production, in part due to the relative ease in producing a high oil yield.

Microalgae have already shown their potential as an alternative source of n-3 LC-PUFA. In this study, 5 different microalgal species (Isochrysis, Nannochloropsis, Phaeodactylum, Porphyridium and Schizochytrium) were added to an acidic model system and screened on their potential use in acidic food matrices. The impact of mechanical and thermal processing on the model systems was studied by analyzing the amount of n-3 LC-PUFA, free fatty acids, carotenoids, lipid polymers and the oxidative stability. A (limited) reduction of n-3 LC-PUFA was observed. Thermal alterations combined with the presence of free fatty acids seemed to be the causing factor for this decrease. Furthermore, the oxidative stability of model systems enriched with photoautotrophic microalgae was significantly higher than of those enriched with heterotrophic microalgae. It can therefore be concluded that photoautotrophic microalgae low in initial free fatty acid content are a promising source of n-3 LC-PUFA in thermally processed acidic food systems. ispartof: FOOD CHEMISTRY vol:268 pages:441-450 ispartof: location:England status: Published online

The aim of this study was to evaluate nutrient digestibility, growth performance, biometry, dressing out parameters, fillet muscle proximate and fatty acid composition of European sea bass (Dicentrarchus labrax, L.) of nearly marketable size, fed increasing levels of a freeze-dried biomass of Isochrysis sp. (clone T-ISO) as a partial substitute for protein and lipid from fish derivatives, in diets where the level of n-3 long chain (LC) PUFA were reduced through a partial replacement of fish oil for crude palm oil. Since diets including the test ingredients could possibly result in changes of certain quality attributes, fish were also subjected to overall sensory evaluation by a trained panel of assessors according to a triangle test. Three diets were formulated to be grossly iso-nitrogenous (N, 7.5 % dry matter). A preparation in which fish meal/trimmings and fish oil were the major protein and lipid sources was used as a positive control diet. Two test complete diets were obtained from the control preparation so that approximately 10 and 20% crude protein from a high quality fish meal and 18 and 36% lipids from fish oil were supplied by the dried microalgae biomass. To stress the role of Isochrysis sp. as a source of n-3(LC)PUFA, the diets including increasing levels of the microalgae biomass were made grossly iso-caloric-lipidic by replacing a part of fish oil with palm oil which is known to be virtually free from n-3 PUFA. Each diet was fed to apparent satiety to quadruplicate groups of sea bass (142 g) over 121 days. The results have shown that replacing up to 20% crude protein from fish meal with a dried Isochrysis biomass and up to 36% fish lipid for those supplied by the microalgae in a diet with reduced level of fish oil, did not adversely affect feed intake or growth performance relative to controls even if the highest substitution rate resulted in a decline (P

For decades, the microalgae Isochrysis spp. have been widely utilised as a live feed in aquaculture practices. This species possesses a number of favourable characteristics, notably its long-chain omega-3 polyunsaturated fatty acid (LC n-3 PUFA) content; primarily docosahexaenoic acid (DHA, 22:6n-3). This article describes the lipid class content and composition of this microalga grown in batch culture, covering the entirety of lag, log and stationary growth phases. The total lipid was highest in the lag phase (27 pg/cell). Total lipid significantly decreased in the exponential growth (7 pg/cell), then steadily increasing for the remainder of growth. The increase in total lipid was due to the accumulation of neutral lipid in the form of triacylglycerides. The DHA content (pg/cell) of the neutral lipid remained relatively unchanged for the duration of growth, with the influx of fatty acids being primarily myristic and palmitic acids. DHA (pg/cell) was found at relatively uniform amounts across all lipid classes. However, the DHA content as a percentage differed greatly between classes. The polar lipid class had a significantly higher DHA content, which peaked at 38 % of all polar lipid in log growth. The primary PUFA species present in the glycolipid class was stearidonic acid (18:4n-3). This work gives an overview of the lipid content and composition of Isochrysis sp. (T-Iso) over the entirety of its growth under batch culture. The lipid profile for this species at different stages of culture provides a basal data set that is useful for comparative studies using this organism.

Isochrysis is a genus of marine algae without cell wall and capable of accumulating lipids. In this study, the lipid production potential of Isochrysis was assessed by comparing 15 Isochrysis strains with respect to their growth rate, lipid production, and fatty acid profiles. Three best strains were selected (lipid productivity, 103.0~121.7 mg L-1 day-1) and their lipid-producing capacities were further examined under different controlled parameters, e.g., growth phase, medium nutrient, and light intensity in laboratory cultures. Furthermore, the three Isochrysis strains were monitored in outdoor panel photobioreactors with various initial cell densities and optical paths, and the strain CS177 demonstrated the superior potential for outdoor cultivation. A two-stage semi-continuous strategy for CS177 was subsequently developed, where high productivities of biomass (1.1 g L-1 day-1) and lipid (0.35 g L-1 day-1) were achieved. This is a comprehensive study to evaluate the lipid-producing capability of Isochrysis strains under both indoor and outdoor conditions. Results of the present work lay a solid foundation for the physiological and biochemical responses of Isochrysis to various conditions, shedding light on the future utilization of this cell wall-lacking marine alga for biofuel production.

The aim of this work was to find alternative low-cost and environmentally friendly rearing substrates for the growth of Hermetia illucens (HI) (Diptera, Stratiomydae), used as feed. At this purpose, insect feeding substrates based on the re-use of coffee silverskin, the main waste product of the coffee-roasting industry, enriched with various percentages of microalgae (i.e., Schizochytrium sp. or Isochrysis sp.), were tested. The fatty acid profile, as well as the relative amount of lipids, proteins and carbohydrates (these latter calculated as ratio to the total biomass of the sample) of ingredients, insect feeding substrates and HI prepupae, were determined for the first-time coupling Gas Chromatography-Mass Spectrometry and Fourier Transform Infrared Spectroscopy. A multivariate statistical analysis (Principal Component Analysis) was performed to better read into results. In general, the inclusion of microalgae caused in both feeding substrates and in HI prepupae an increase in the relative amount of lipids and proteins, improving their nutritional value. Higher amounts of unsaturated fatty acids, particularly of omega-3, and good nutritional indices were detected in HI prepupae reared on substrates enriched with 10%, 20% or 25% of Schizochytrium sp. with respect to HI prepupae fed with coffee silverskin enriched with Isochrysis sp., suggesting them as new nutraceutical ingredients for future functional feed and food. In addition, the substrate enriched with a 10% inclusion level of Schizochytrium sp. has to be considered the most convenient one since a greater inclusion of microalgae did not promote additional benefits in terms of nutritional value of HI prepupae.

SUMMARY The nitrogenous resource used to promote algal growth has cost implications for mass culture processes. The present study therefore aimed to determine the effect of different nitrogenous resources (nitrate, ammonium and urea) on various performance parameters (growth, final cell yield, pigmentation, lipid yield and cellular and sub-cellular characteristics) in Isochrysis galbana. Growth rate was unaffected by nitrogenous resource, but the final cellular yield in the nitrate and urea treatments far exceeded that evident in the ammonium treatments. The reduced cell yield in ammonium treatments and the earlier onset of the stationary phase was brought about by nitrogenstarvation due to an increase in pH and resultant ammonia volatilization. This starvation initiated an early onset of lipid accumulation, chlorophyll depletion and an increase in the carotenoid to chlorophyll ratio relative to the other nitrogen (N) source treatments. Hence, in spite of being potentially the preferred source of N by algae (due to its reduced state), ammonium-nitrogen is undesirable for mass culture. The performance parameters of Isochrysis grown in urea (an organic N source) and nitrate (an inorganic N source) were similar, but lipid accrued earlier in cells grown in medium supplemented with urea. This is advantageous for lipid acquisition for the production of biodiesel since it would reduce the duration of photobioreactor runs. Urea is easily available and considerably cheaper than all the other N sources tested and is thus recommended as the nitrogenous resource for large-scale culture of I. galbana for biodiesel production.

Microalgae are capable of synthesizing a wide range of value-added compounds such as docosahexaenoic acid (DHA) and fucoxanthin. In the present study, the potential for simultaneous production of DHA and fucoxanthin by the marine alga Isochrysis was investigated via strain screening and culture optimization. A comparative analysis of sixteen Isochrysis strains revealed that CCMP1324 was superior with regard to growth and production of DHA and fucoxanthin. In response to various nutritional and environmental cues, CCMP1324 accumulated DHA and fucoxanthin in a coordinated and growth-dependent manner, which reached ~17.1 and 14.1 mg g−1, respectively. A semi-continuous culture strategy leading to high productivities of DHA (9.05 mg L−1 day−1) and fucoxanthin (7.96 mg L−1 day−1) was developed. Taken together, our study represents a pioneering work studying the accumulation coordination between DHA and fucoxanthin in Isochrysis. These findings provide valuable insights into future exploration for the integrated production of high-value compounds.

Some marine microalgae, such as Isochrysis sp., produce high-melting (∼70 °C) lipids known as long-chain alkenones that detrimentally affect biodiesel fuel quality. A method has been developed for the production of an alkenone-free Isochrysis biodiesel. This material was prepared on sufficient scale to allow for extensive analysis according to ASTM standards. Results revealed that while cold flow improved by removal of these high-melting components and lubricity and glycerol content were below maximum levels prescribed in the standards, other properties dependent on fatty acid methyl ester (FAME) structure and composition such as oxidative stability failed to meet ASTM specifications. Both the cetane number and kinematic viscosity were lower than what would be calculated based on FAME content. This has been explained in part by 6–8% non-FAME contaminants in the tested samples.

We compared the development and fatty acid content of the harpacticoid copepods Tachidius discipes and Tisbe sp. fed with different microalgal species (Dunaliella tertiolecta, Rhodomonas sp., Phaeodactylum tricornutum, Isochrysis galbana and a concentrate of Pavlova sp.), which differed in cell size and fatty acid composition. Tisbe could develop in 11 days with every alga to the same average stage, whereas Tachidius developed poorly when fed with Isochrysis and Dunaliella. Feeding with Phaeodactylum resulted in a fast development of both copepods at low algal concentrations. However, reproduction was higher with Rhodomonas as food than with the other algae. Fatty acid compositions of copepods were influenced by their food source, but both were able to convert docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from precursors. Tachidius fed with Rhodomonas or Phaeodactylum was closest to the DHA/EPA/arachidonic acid (ARA) ratio of 10 : 5 : 1 considered optimal for some marine fish larvae. Tachidius showed similar development and reproduction capacity as Tisbe, but requested higher absolute fatty acid contents in the diet. Tisbe was superior in the utilization of bacteria as additional food source and the bioconversion of precursor fatty acids. Phaeodactylum and Rhodomonas are recommendable food sources for both copepod species, but Phaeodactylum is more easily cultured.

The purpose of this work was to evaluate two food grade solvent systems, hexane/isopropanol (3:2; HI) and hexane (H), for the extraction of lipids from different omega-3 LC-PUFA rich microalgae: Isochrysis galbana, Nannochloropis gaditana, Nannochloropsis sp. and Phaeodactylum tricornutum. We not only focused on differences in lipid yield, but also lipid class, omega-3 LC-PUFA, carotenoid and sterol yields. Furthermore, an estimation of the feasibility of these microalgae oils as an alternative for fish oil was made. For all tested microalgae species, the highest food grade lipid, lipid class, omega-3 PUFA, carotenoid and sterol yield were obtained with HI, with a general recovery highest from Isochrysis, lowest from both Nannochloropsis species, and intermediate from Phaeodactylum. Total lipid recovery values between 14 and 76% depending on solvent and species were obtained. It was also shown that the omega-3 fatty acid content of all oils was quite similar, while only the H extract was enriched in neutral lipids. Carotenoids were co-extracted in a significant amount, although the content in the various oils was quite different.

An oleaginous, unicellular, marine microalga termed IOAC724S was isolated from the South China Sea. Morphology and genetic analyses indicated it belongs to the genus Isochrysis. Gas chromatography (GC) results showed that more than 10 types of fatty acids existed in Isochrysis sp. IOAC724S and that 90% of them were suitable for lipid production. The culture conditions suitable for cell growth were progressively optimized through photosynthetic and respiratory analyses. The optimal culture conditions were: photon flux 200-500 mu mol m (2-) s (1), temperature 35 degrees C during daytime and 24 degrees C at night, pH value between 7 and 8, NaNO3 160 g m (-3) and NaH2PO4 center dot 2H(2)O 80 g m(-3) for starting culture. When microalgal cultures were exposed to these optimal conditions, the specific growth rate reached to 0.26 d (1) on average and 1.0 d(-1) in MAX. Lipid production was optimized through nutrient starvation processes, including nitrate or phosphate deprivation and simultaneous nitrate and phosphate deprivation. The highest lipid mass fraction of dry cell weight (about 55.6%) was obtained after the stationary phase algal culture was transferred into phosphate-free medium for 3 days. GC data demonstrated that the enhancement of lipid accumulation in algal cells maintained under nutrient starvation came mainly from an increase of C16:0 and C18:1 fatty acids; however, the lipids with a chain length appropriate for fuel use (C14 to C18) were unchanged at 90% mass fraction of the dry cell weight. Based on these good characteristics, Isochrysis sp. IOAC724S appeared to be a strong candidate for lipid production. (C) 2013 Elsevier Ltd. All rights reserved.

Four different omega-3 rich autotrophic microalgae, Phaeodactylum tricornutum, Nannochloropsis oculata, Isochrysis galbana and Chlorella fusca, were supplemented to the diet of laying hens in order to increase the level of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) in egg yolk. The microalgae were supplemented in two doses: 125 mg and 250 mg extra n-3 PUFA per 100g feed. Supplementing these microalgae resulted in increased but different n-3 LC-PUFA levels in egg yolk, mainly docosahexaenoic acid enrichment. Only supplementation of Chlorella gave rise to mainly α-linolenic acid enrichment. The highest efficiency of n-3 LC-PUFA enrichment was obtained by supplementation of Phaeodactylum and Isochrysis. Furthermore, yolk colour shifted from yellow to a more intense red colour with supplementation of Phaeodactylum, Nannochloropsis and Isochrysis, due to transfer of carotenoids from microalgae to eggs. This study shows that besides Nannochloropsis other microalgae offer an alternative to current sources for enrichment of hen eggs. publisher: Elsevier articletitle: Impact of feed supplementation with different omega-3 rich microalgae species on enrichment of eggs of laying hens journaltitle: Food Chemistry articlelink: http://dx.doi.org/10.1016/j.foodchem.2013.06.078 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved. ispartof: Food Chemistry vol:141 issue:4 pages:4051-4059 ispartof: location:England status: published

In this study, the potential of 10 algae species for biodiesel production were evaluated by determining their fatty acid profiles, biodiesel properties besides growth rate, biomass concentration and lipid productivity. Among seven strains with high growth and lipid accumulation properties, excluding Kirchneriella lunaris and Lyngbya kuetzingii, five species Selenastrum capricornutum, Chlorella vulgaris, Scenedesmus obliqnus, Phaeodactylum tricornutum and Isochrysis sphacrica were finally selected for biodiesel production due to their possessing higher lipid productivity and favorable biodiesel properties. The best strain was P. tricornutum, with lipid content of 61.43 ± 0.95%, lipid productivity of 26.75 mgL(-1) d(-1), the favorable fatty acid profiles of C16-C18 (74.50%), C14:0 (11.68%) and C16:1 (22.34%) as well as suitable biodiesel properties of higher cetane number (55.10), lower iodine number (99.2 gI₂/100g) and relatively low cloud point (4.47 °C).

International audience; To investigate the nutritional value of the marine micro-alga Isochrysis galbana Tahitian Isochrysis strain (T.iso) as an alternative feed for aquaculture during culture age, its biochemical composition was studied under autotrophic and controlled culture conditions at different growth stages: exponential phase, early and late stationary phases and decay phase. Analysis showed that C14:0, C16:0, C16:1, C18:4 (n-3) and C22:6 (n-3) were the most abundant fatty acids in this alga at different growth stages. The highest values of monounsaturated fatty acids were recorded at the late stationary and the decay phases. However, the highest levels of polyunsaturated fatty acids were observed at the early stationary phase. At all growth stages, I. galbana (T.iso) contained arabinose, xylose, mannose, galactose and glucose. Glucose represented the main sugar, and its content per dry alga biomass weight increased with increasing age of the culture and reached about fourfold in the decay phase. The maximum protein content was also observed during this last phase.

Acute toxicity of water soluble fraction (WSF) of diesel fuel was assessed by evaluating its effects on growth of two marine microalgae, Isochrysis and Chaetoceros. Pure cultures of each of the two microalgae were exposed to concentrations of 0% (controls), 5%, 10%, 15% and 20% of diesel WSF (in triplicates) and allowed to grow for 96 hours. Cell density was determined in each of the culture vessels every 24 hour. Cell density growth rate in every treatment, percentage growth inhibition by various concentrations and IC50 of diesel WSF on the two microalgae were determined following standard methods. While control cultures recorded exponential growth within 96 hour, the four WSF concentrations resulted in inhibition of cell growth of the two microalgae species every 24 hour. Cell growth inhibition effect increased significantly (p0.05). Ecological implications of the growth inhibition effects of diesel WSF microalgae were discussed.Key Words: Cell density, water soluble fraction (WSF), concentration, growth inhibition, 96 hour IC50, Isochrysis, Chaetoceros

Natural alternatives antioxidant source has become a trending topic in the past decades to replace synthetic antioxidant. Microalgae have been mentioned to show interesting bioactive properties and one of them is its antioxidant activity. This study aims to evaluate the potential of three microalgae Dunaliella salina, Tetraselmis chuii and Isochrysis galbanaas new source of natural antioxidant. Proximate analysis and total phenolic content of D. salina, T. chuii and I. galbanas were determined. Antioxidant activity of methanolic extracts of these three species prepared in different concentration (50, 100, 250, 500, and 1000 ppm) was performed through DPPH assay. I. galbana clone Tahiti demonstrated a highest antioxidant potential with 61.64 of inhibition at 50 ppm followed by D. salina with 58.45 % of inhibition and T. chuii with 52.58 % of inhibition. I. galbana clone Tahiti was the best antioxidant with total phenol content of 17.798 mg GAE g-1 extract at 50 ppm; followed by T. chuii 16.868 mg GAE g-1 extract and the lowest was D. salina with 4.672 mg GAE g-1 extract. Results suggest that these microalgae posses antioxidant potential which could be considered for future applications in medicine, dietary supplements, cosmetics or food industries.

The need to replace petroleum fuels with alternatives from renewable and more environmentally sustainable sources is of growing importance. Biomass-derived biofuels have gained considerable attention in this regard, however first generation biofuels from edible crops like corn ethanol or soybean biodiesel have generally fallen out of favor. There is thus great interest in the development of methods for the production of liquid fuels from domestic and superior non-edible sources. Here we describe a detailed procedure for the production of a purified biodiesel from the marine microalgae Isochrysis. Additionally, a unique suite of lipids known as polyunsaturated long-chain alkenones are isolated in parallel as potentially valuable coproducts to offset the cost of biodiesel production. Multi-kilogram quantities of Isochrysis are purchased from two commercial sources, one as a wet paste (80% water) that is first dried prior to processing, and the other a dry milled powder (95% dry). Lipids are extracted with hexanes in a Soxhlet apparatus to produce an algal oil ("hexane algal oil") containing both traditional fats (i.e., triglycerides, 46-60% w/w) and alkenones (16-25% w/w). Saponification of the triglycerides in the algal oil allows for separation of the resulting free fatty acids (FFAs) from alkenone-containing neutral lipids. FFAs are then converted to biodiesel (i.e., fatty acid methyl esters, FAMEs) by acid-catalyzed esterification while alkenones are isolated and purified from the neutral lipids by crystallization. We demonstrate that biodiesel from both commercial Isochrysis biomasses have similar but not identical FAME profiles, characterized by elevated polyunsaturated fatty acid contents (approximately 40% w/w). Yields of biodiesel were consistently higher when starting from the Isochrysis wet paste (12% w/w vs. 7% w/w), which can be traced to lower amounts of hexane algal oil obtained from the powdered Isochrysis product.

© 2016. Two microalgal species, Isochrysis galbana and Nannochloropsis oculata, were supplemented to the diet of laying hens, in either non-disrupted or disrupted (by high pressure homogenization) form, to examine the effect of the presence of a cell wall on the omega-3 long chain polyunsaturated fatty acid (n. -. 3 LC-PUFA) enrichment in the egg yolk. Only supplementation of Nannochloropsis led to significant differences in enrichment by supplementation of the two forms, with the highest enrichment obtained with the HPH-disrupted form. This confirms the presence of a rigid cell wall for this species, which reduces the bioaccessibility of the n. -. 3 PUFA. The needed conversion reaction from EPA to DHA on the other hand did not seem to effect the enrichment, since the same n. -. 3 LC-PUFA enrichment was obtained with the supplementation of the DHA source Isochrysis and the EPA source Nannochloropsis, the last in HPH-disrupted form.Next to the microalgal species, fish oil was also supplemented to the diet of the laying hens. Fish oil resulted in a higher enrichment in comparison with the microalgal species, either non-disrupted or HPH-disrupted. This might suggest a difference in bioaccessibility of the n. -. 3 PUFA when added as oil or biomass. publisher: Elsevier articletitle: The cell wall of autotrophic microalgae influences the enrichment of long chain omega-3 fatty acids in the egg journaltitle: Algal Research articlelink: http://dx.doi.org/10.1016/j.algal.2016.03.015 content_type: article copyright: © 2016 Published by Elsevier B.V. ispartof: Algal Research vol:16 pages:209-215 status: published

Even though the microalgal species of Isochrysis and Pavlova are widely used as live food in bivalve hatcheries, they are difficult to culture in mass during the summer season. Therefore, the present study was conducted to determine the optimum species or strains of Isochrysis and Pavlova to produce good growth and high contents of fatty acids at temperatures over . Four species of Isochrysis (I. galbana KMMCC12, I. galbana KMMCC214, I. aff. galbana, and Isochrysis sp.) and four of Pavlova (P. lutheri, P. gyrans, P. viridis, and Pavlova sp.) were cultured at , , and , and then analyzed for specific growth rate and fatty acid composition. Microalgae were cultured in f/2 medium at 23 psu and continuous light of photons . For the I. galbana, growth rates were highest at and decreased at to the level observed at . I. galbana (KMMCC12) and Isochrysis sp. cultured at and , respectively, exhibited the highest growth rates of all Isochrysis species. In terms of fatty acids, I. galbana (KMMCC12) contained higher contents of PUFA and n-3 HUFA at than did Isochrysis sp. For species of Pavlova, growth rates of P. gyrans and P. viridis at and , respectively, were higher than those of the other Pavlova species. In particular, P. viridis grew as well at as it did at . However, P. lutheri and Pavlova sp. did not grow at . In terms of fatty acids, P. viridis cultured at also exhibited higher contents of PUFA and n-3 HUFA, as compared to P. gyrans. Based on these results, we suggest that I. galbana (KMMCC12) and P. viridis are suitable species for mass culture during the high temperature season.

Algal allelopathy is an ecological or physiological phenomenon that has focused attention on the interactions among algae and the production of algal toxins.A species of marine bloom-forming microalga: Amphidinium carterae was selected in the present study to estimate its potentially allelopathic effects on other species of microalgae.The cell-free filtrates of A.carterae in two growth phases: exponential grwoth phase(abbreviated as growth phase Ⅰ) and stationary growth phase(abbreviated as growth phase Ⅱ) were prepared,and its inhibitory effects on growth of other species of marine microalgae were studied under stable environmental conditions(temperature,light and illuminating periodicity,etc.).The cell-free culture filtrates were prepared firstly when A.carterae were cultured phaseⅠand phaseⅡ,which was about the the growth 7th and 17th respectively,and enriched with f/2 medium.The above prepared culture filtrates were used to culture 4 species of marine microalgae: Skeletonema costatum、Prorocentrum micans、Scrippsiella trochoidea and Isochrysis golbana.Moreover,the crude extractions in the cell-free filtrate of A.carterae of growth phaseⅡ were extracted by GC/MS,and the major components were analyzed.Results showed that: in the enriched cell-free filtrates,S.costatum were obviously inhibited in either filtrates of phase I(F=15.18475,P=0.002980.05) or phase Ⅱ(F=6.24559,P=0.031490.05) as compared to that in the control which in f/2 enriched medium,but the cell numbers of S.trochoidea were only about 79.3% and 68.9% in filtrates prepared from phaseⅠand phaseⅡ as compared to the control by the end of experiment.As to P.micans,its growth was obviously suppressed(F=4.84438,P=0.049250.05) in the filtrate prepared from phaseⅡduring the last 3 days.Little inhibition was observed in I.golbana in either filtrates prepared from either phases(P0.05).Cell-free filtrate cultures experiment of A.carterae is one of the basic approaches on allelopathy research.Results in the present study suggested that A.carterae secreted or released some substances into the culture medium,which inhibited the co-cultured S.costatum and P.micans,and these inhibitory effects could not caused by light,nutrients or cell contact to gain a competitive advantage.Many algae could release allelochemicals into the environment which may alter phytoplankton growth to enhance its predominance.Besides,growth of these two species was more inhibited in enriched cell-free filtrate prespred from growth phaseⅡ than that from phaseⅠ.It also proved that the allelochemical effects on algae were species-specific because growth of S.costatum and P.micans was inhibited,but exerted little effects on S.trochoidea and I.golbana.Another experiment was performed to further prove the allelopathic effect of A.carterae.The crude extractions from cell-free filtrates of A.carterae at different concentrations were added into S.costatum and P.micans culture media,found that cells dissolved in higher concentration after many hours.It is noted that the crude extractions had the function of dissolving some algal cells.Then the crude extractions were analyzed by GC/MS.Four components in the crude exactions were suspected to have the allelopathic effects,they were Butylated Hydroxytoluene,Butyl citrate,Benzene,1-Chlorodifluoromethoxy-4-nitro-,and Benzyl butyl phthalate,among with Butylated Hydroxytoluene(BHT) was reported with oxidative characteristic and was used as an antioxidant additive.Results in the present study brought light on the hypothesis that A.carterae could realese allelochemical(s);however,deep research should carry out to explain the possible inhibiting mechanism.

© 2018 Microalgal lipids have a huge potential in several applications such as biofuels, food and feed. However, enzymatic lipolytic reactions during wet storage cause the formation of substantial amounts of free fatty acids (FFA), which give several problems for these applications. In this study, a full factorial (32) design with varying time and temperature was used to optimize a heat treatment, that inactivates lipolytic enzymes in the wet paste of T-Isochrysis lutea. Therefore, the FFA and lipid content were evaluated at three time points (0, 3 and 7 days) during wet storage at 4 °C. A treatment of at least 8 min at 80 °C was found to inactivate the lipolytic enzymes. A second experiment elucidated that this optimal treatment had no negative impact on fatty acid composition, peroxide value, phenolic content or carotenoid content. A short heat treatment, thus, enables wet storage of microalgal paste to several days at 4 °C. ispartof: ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS vol:38 status: published

Three Isochrysis galbana strains, one I. galbana “substrain”, and one Nannochloropsis sp. strain were grown in nutrient replete conditions at 15, 20, 25, and 30 °C. The interactive effect of temperature and isolate on growth rate, cell volume, production, dry weight, protein content, carbohydrate content, and total lipid content was examined. Nannochloropsis sp., growth rate had no relation with temperature; all I. galbana isolates increased linearly with temperature, with no significant differences. Cell volume and dry weight decreased linearly with temperature, with significant isolate and species differences. Biovolume-production did not vary significantly with temperature, but significant isolate and species differences occurred. Although significant temperature isolate interactions existed, no consistent trends in the change of protein, carbohydrate, and lipid with temperature occurred. We indicate a need to consider temperature induced affects in application using microalgae isolates, at various taxonomic levels, as some intraspecific differences were as great as interspecific differences.

To determine variability of marine microalgal lipids during cell growth and respiration, and within intracellular structures, we conducted two series of experiments: (1) batch culturing Isochrysis sp., Gymnodinium sp., Platymonas subcordiforus , Heterosigma akashiwo Hada, and Skeletonema costatum with lipid analysis for cell samples collected in exponential growth and stationary phase respectively; and (2) batch culturing Isochrysis sp. and Gymnodinium sp. from exponential growth to stationary phase and followed by dark incubation with progressive lipid analysis. Moreover, membrane and intracellular storage fatty acids were separated using Si-gel chromatography from representative samples of each species in the second experiment (respectively in exponential growth, stationary phase, and dark respiration). Results from the first experiment showed that no matter how differently microalgae grew, their lipid yields were 4–38 × higher in stationary phase than in exponential growth phase. Progressive lipid analysis in the second experiment indicated that total fatty acid (FA) yields in two microalgal cultures continuously increased throughout exponential and stationary phases but total neutral lipid (NL) yields slowed or stopped to increases in stationary phase. During dark incubations, total FA yields decreased steadily in both Isochrysis (with constant cell density) and Gymnodinium (with declining cell density) cultures but total NL yields decreased only in Gymnodinium culture. Lipid compositions and proportions of membrane vs. intracellular fatty acids varied differently with growth phases and respiration in two cultures. This study suggests that the effect of cell growth phase on cellular lipid yield and composition is species-dependent and is likely related to the capacity of cells to synthesize membrane vs. intracellular storage lipids.

Biomass and lipid productivity, lipid content, and quantitative and qualitative lipid composition are critical parameters in selecting microalgal species for commercial scale-up production. This study compares lipid content and composition, and lipid and biomass productivity during logarithmic, late logarithmic, and stationary phase of Nannochloropsis sp., Isochrysis sp., Tetraselmis sp., and Rhodomonas sp. grown in L1-, f/2-, and K-medium. Of the tested species, Tetraselmis sp. exhibited a lipid productivity of 3.9-4.8 g m(-2) day(-1) in any media type, with comparable lipid productivity by Nannochloropsis sp. and Isochrysis sp. when grown in L1-medium. The dry biomass productivity of Tetraselmis sp. (33.1-45.0 g m(-2) day(-1)) exceeded that of the other species by a factor 2-10. Of the organisms studied, Tetraselmis sp. had the best dry biomass and/or lipid production profile in large-scale cultures. The present study provides a practical benchmark, which allows comparison of microalgal production systems with different footprints, as well as terrestrial systems.

The variation of fatty acid (FA) content and composition of the microalgal production (Isochrysis sp., Pavlova lutheri and Chaetoceros muelleri) in a continuous large-scale production system (500-L bags) used in hatcheries were analysed. The variation of the FAs was analysed in replicate bags over time for the different species. Total FA content (pg cell−1) increased significantly (p

Growth of marine copepods is influenced by feed. The purposes of this trial were to observe both growth and fatty acid compositions of harpacticoid copepod nauplii, Tisbe holothuriae by feeding with several microalgal species in laboratory: (A) Isochrysis tahiti; (B) Nannochloropsis oculata; (C) Rhodomonas sp., and (D) Tetraselmis chuii. The trial was carried out for 35 days with randomized complete design and triplicates in each treatment. The results showed that final copepod nauplii densities were not significantly different (P>0.05) in all treatments. However, lipid content of copepod nauplii fed with T. chuii was significantly higher (P

Both food type and quantity have a strong effect on the egg production, RNA:DNA ratio and RNA content of the copepod Acartia sinjiensis. Copepods were fed limiting (150 μg Cl−1) and non-limiting (1500 μg Cl−1) concentrations of Tetraselmis chuii (Prasinophyceae), Pavlova salina and Isochrysis aff. galbana (Prymnesiophyceae), and Chaetoceros muelleri (Bacillariophyceae). Saturation of copepod egg production was estimated for Tetraselmis and Pavlova offered in a wide range of concentrations (0–1500 μg Cl−1). Under non-limiting food conditions, A. sinjiensis produced more eggs when fed Tetraselmis (mean 17.6 eggs female−1day−1−efd) and Pavlova (14.2 efd), and produced fewer eggs when fed Isochrysis (9 efd) and Chaetoceros (7.6 efd). RNA: DNA ratio (mean 7) and individual RNA content (mean 2 μg RNA ind−1) were significantly higher in females fed abundant Tetraselmis in comparison to the other algae. Under food-limiting conditions, A. sinjiensis could still produce eggs when fed Pavlova (3.3 efd) and Tetraselmis (1.7 efd), but failed to produce eggs when fed Isochrysis and Chaetoceros. In food-limited females RNA:DNA ratios and individual RNA content were variable and lower than animals fed non-limiting algae concentrations. The saturation of egg production was 714 μg Cl−1 for Tetraselmis and 509 μg Cl−1 for Pavlova. The relationship of RNA:DNA ratio and food concentration followed a similar function to egg production, with a saturation level of 509 μg Cl−1 for Tetraselmis. Egg production was positively correlated with female size only in animals fed Tetraselmis at 1500 μg Cl−1; all other algae and food concentrations were uncorrelated with female size. Of the algal species tested, Tetraselmis and Pavlova are candidate algae for use in A. sinjiensis culture. Egg production saturates around 500 μg Cl−1, as is the case in other Acartia species. Both RNA:DNA ratio and RNA content of the females were sensitive to different food type and concentration, and have the potential to be used as an alternative method for the identification of optimal food for use in Acartia culture. These observations have important implications for the understanding of the dynamics and productivity of this species in coastal environments of tropical Australia, and also its potential use in aquaculture and ecotoxicology.

Arachidonic acid (ARA, 20:4 n − 6) is essential for oysters and has been implicated in reproduction and immune response of different mollusk species, probably by modulating the levels of prostaglandins. We tested the effect of dietary ARA on reproduction, PGE 2 levels, and some immune variables in Crassostrea corteziensis . Oysters were fed Isochrysis affinis galbana , clone Tahiti (T-iso) for three weeks, which has low ARA and high DHA (22:6 n − 3) levels and that was supplemented with 0, 1 and 9% ARA-rich lipid emulsions at 10% of algal dry weight biomass using a once-daily batch system to supply the microalgae. Survival and growth were not affected by the ARA enrichment. More gonadic tissue was found in oysters fed 1% ARA but oysters fed the 9% ARA were in a more advanced stage of maturation. ARA-enrichment did not affect fatty acid concentration in membrane phospholipids, but ARA concentration was higher in triacylglycerols of oysters fed 9% ARA compared to 0% ARA diet. PGE 2 and/or PGF 1 α concentration was higher in oysters fed the 9% ARA diet. Total hemocyte count was not affected by ARA enrichment, but the proportion of granulocytes and the superoxide anion activity (SOA) in relation to total hemocyte count were higher in oysters fed the 1% ARA diet. These results suggest that feeding moderate levels of ARA to oysters can boost immune system response and oocyte production. However, high levels of ARA favor final maturation and advanced stages of vitellogenesis but possibly at the expense of immune response.

The growth of a temperate and a tropical strain of Isochrysis was studied at four temperatures and three light intensity levels. All algal cultures were grown in an enriched artificial seawater medium under constant illumination and were bubbled with air enriched with 0.1% CO2. Culture density (cells/ml) was measured periodically during exponential growth. Average growth rates for each combination of temperature and light intensity are presented as doublings/day. Observations of growth under the various culture conditions indicate that T-ISO (tropical strain) grows rapidly over a much broader range of temperatures than does I. galbana. Variations in growth at different light intensity levels suggest that the optimum light level increases as a function of temperature for T-ISO and that the growth of I. galbana is inhibited by high levels of light (1500 μW/cm2). The relative value of both strains as food for larval and juvenile oysters and the advantages and limitations of large scale culture are discussed.

Feeding experiments using commonly-cultured algae were conducted with purple-hinge rock scallops, Hinnites multirugosus Gale, to suggest the application of these algae to hatchery culture of scallops. The uptake of finely divided particulate matter was also studied to ascertain the possible importance of detritus as a supplemental food for the rock scallop. A 1:1:1 mixture by culture volume of Tahitian Isochrysis, Tetraselmis suecica, and Dunaliella salina appeared to be superior as a diet for juvenile rock scallops. Significant growth also occurred in juvenile rock scallops fed T-Isochrysis, T. suecica, Isochrysis galbana, and Rhodomonas sp. Gymnodinium splendens, Monochrysis lutheri, and Dunaliella salina fed alone were poor foods for juvenile rock scallops. Finely divided particulate matter as radiolabeled abalone fecal matter was utilized as food. Significant radioactivity appeared in DNA, RNA, lipid, protein, carbohydrate, and free-reducing substances after one week providing evidence that particulate matter was incorporated into juvenile rock scallop metabolic pathways.