Isochrysis Sp Research Articles

Beneficial impact of AgNPs on fucoxanthin production and evaluation of phytochemical variations in Isochrysis sp.

Silver nanoparticles (AgNPs) are commonly transformed into various engineered nanomaterials for various applications, leading to their unavoidable disposal in the environment. Despite their toxicity, knowledge gaps remain regarding the metabolic perturbations induced by AgNPs on phytoplankton, which play a crucial role in global biogeochemical cycles and food-web dynamics. This study aimed to utilize AgNPs to elicit stress response of Isochrysis sp. KRJ-105, for enhancing fucoxanthin production, a valuable pigment with anti-inflammatory and antioxidant properties. The microalgae were treated with different AgNP concentrations (10, 30, 50, 70, and 100 mg/L) for 12 days, and the results showed that the addition of 50 mg/L AgNPs significantly promoted cellular fucoxanthin biosynthesis (34.61 ± 0.50 mg/g), a 5.94 mg/g higher production compared to the control (28.67 ± 1.01 mg/g). This study represents the first-time report of higher fucoxanthin production in Isochrysis sp. compared to previous reports in the last decade. Furthermore, AgNPs induced stress conditions in Isochrysis sp., also reflected in growth rates and alterations in biochemical composition, including total carbohydrate, total protein, lipid, carotenoid, and reactive oxygen species (ROS) content. Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDAX) analysis revealed the interaction of AgNPs with the cell surface of Isochrysis sp. KRJ-105. These findings provide novel insights into microalgal interactions with nanoparticles, offering fundamental knowledge on physiochemical changes induced in Isochrysis sp., and its future development in cultivation aspects for superior commercial fucoxanthin production.

The influence of spermidine on the build-up of fucoxanthin in Isochrysis sp. Acclimated to varying light intensities

Spermidine is a type of important growth regulator, which involved in the biosynthesis of photosynthetic pigments, and has the function of promoting cell proliferation. In this study, Isochrysis sp. was selected as the research object to explore the effects of spermidine supplementation on the growth of algal cells and fucoxanthin synthesis under different light intensities. The results showed that the cell density (5.40 × 106 cells/mL) of algae were the highest at 11 days under the light intensity of 200 μmol·m−2·s−1 and spermidine content of 150 μM. The contents of diadinoxanthin (1.09 mg/g) and fucoxanthin (6.11 mg/g) were the highest when spermidine was added under low light intensity, and the growth of algal cells and fucoxanthin metabolism were the most significant. In the carotenoid synthesis pathway, PDS (phytoene desaturase) was up-regulated by 1.96 times and VDE (violaxanthin de-epoxidase) was down-regulated by 0.95 times, which may promote fucoxanthin accumulation.

Lithium–Sodium Fly Ash-Derived Catalyst for the In Situ Partial Deoxygenation of Isochrysis sp. Microalgae Bio-Oil

The catalytic potential of Na and LiNa fly ash (FA) obtained through a simple solid-state synthesis was investigated for the pyrolysis of Isochrysis sp. microalgae using a fixed bed reactor at 500 °C. While both LiNa-FA and Na-FA catalysts reduced the bio-oil yield and increased char and gas production, LiNa-FA was found to enhance the quality of the resulting bio-oil by decreasing its oxygen content (−25 wt.%), increasing paraffins and olefins and decreasing its acidity. The deoxygenation activity of LiNa-FA was attributed to the presence of weak and mild base sites, which enabled dehydration, decarboxylation, ketonisation, and cracking to form olefins. The bio-oil generated with LiNa-FA contained higher amounts of alkanes, alkenes, and carbonated esters, indicating its capacity to chemisorb and partially desorb CO2 under the studied conditions. These findings suggest that LiNa-FA catalysts could be a cost-effective alternative to acidic zeolites for in situ deoxygenation of microalgae to biofuels.

Extending Omega 3/6 Fatty Acid Pathway in Arabidopsis thaliana using Microalgal Gene Δ6Des for Stearidonic acid and Dihomo-γ-linolenic acid Production

• Microalgal gene Δ6Des was cloned in a binary vector pCAMBIA1303. • F 1 transgenic plants having Δ6Des were viable at a concentration of 25 mg/L of hygromycin medium • Transgenic Arabidopsis thaliana showed novel ω3/6 fatty acids SDA (0.58%) and DGLA (25. 34%) To enhance the quality and quantity of oils in plant systems, specific candidate genes such as desaturase and elongase that can extend the biosynthetic pathways of very long chain poly unsaturated fatty acids (VLCPUFAs) are essential. In general, plant systems are capable of synthesizing essential fatty acids (EFAs). However, incorporation of a preliminary gene, Δ6Desaturase ( Δ6Des ), in the fatty acid biosynthetic pathway will elongate the pathway further to produce successive fatty acids. In this study, Δ6Des gene extracted from the marine microalga Isochrysis sp. was used to extend the omega (ω) 3/6 fatty acid biosynthetic pathway in a model plant Arabidopsis thaliana using Agrobacterium -mediated genetic transformation. Hygromycin-resistant plants were (25 mg/L) used for GUS and GFP assays and for molecular confirmation. GUS assay showed an intense blue color in F 1 transgenic A. thaliana plant tissues grown in the selection medium, which confirmed the presence of GUS gene in the T-DNA region, whereas non-transformed plant tissues such as leaf or stem did not show any blue color. GFP analysis also showed a green fluorescent color in tissues such as leaf, stem, and floral parts of F1 transgenic A. thaliana plants, which confirmed the presence of T-DNA. PCR and Southern blotting analyses also clearly showed the presence of Δ6Des in the T-DNA region of the F 1 transgenic plants. The fatty acid profile of F 1 transgenic plants showed the production of new fatty acids such as stearidonic acid (SDA-0.58%) and dihomo-γ-linolenic acid (DGLA-25.34%) that were not observed in non-transformed control plants. All these results showed the synthesis of new fatty acids in the transgenic plant, which proved that PUFA biosynthetic pathway can be extended in oilseed plants if specific genes are introduced through genetic transformation. This is the first study to report the productions of new fatty acids like SDA and DGLA in A. thaliana using Δ6Des gene from marine microalga Isochrysis sp.

Growth performance of brown-golden marine microalga, Isochrysis sp., cultivated in alternative algal culture media

The present study aimed to evaluate the suitability of introduced algal culture media as an alternative to the general enriched seawater media in the laboratory cultivation of Isochrysis sp., a marine microalga commonly cultivated for aquaculture purposes. Isochrysis sp. was established into culture in three replications using three experimental algal culture media (Walne’s medium as a control, China-contributed culture medium (CCM) and CCM supplemented with vitamins (CCM + Vit)). The experiment was performed with a continuous illumination for a period of seven days at 25±1°C. The effect of introduced algal culture media (CCM and CCM + Vit) on the growth performance of Isochrysis sp. was highlighted. CCM demonstrated promising results for the cultivation of Isochrysis sp. A maximum cell density of 9.16×106 ± 5.40×105 cells mL-1, which corresponded to an instantaneous growth rate (r) of 0.21 cell day-1 and a doubling time (T2) of 3.29 days, was observed in Isochrysis sp. cultivated in CCM. In view of its potential and reduced preparation labour, CCM may be recommended as an alternative to the general enriched seawater media in the cultivation of Isochrysis sp. in laboratories with basic facility as well as small- and medium-scale aquaculture hatcheries.

Population growth and mass production of brackish water cladoceran Eurycercus beringi sp. nov. under different diet and salinity regime, and its role in P. indicus larval rearing

The growth performance and mass production of Eurycercus beringi sp. nov., comes under cladocera isolated from Adyar creek, Chennai fed with different diets includes Chlorella sp, Nannochloropsis sp, Chaetoceros sp, Thalassiosira sp, Tetraselmis sp, Dunaliella sp and Isochrysis sp, rice bran and baker’s yeast as monospecific and mixed diets (1:1) have been investigated. The species reproduce parthenogenetically attained a size range of 300- 1098μm and tolerate salinity range of 3–35‰ with fecundity range of 2–7 numbers with minimum maturation period of 3–6 days depending on quality of feed with minimum aeration. Salinity found to play a significant role in survival with maximum survival at 25 ‰. There is a significant difference (p<0.05) in survival at lower and higher salinity. The highest fecundity was observed in the treatment fed with Chlorella and Nannochloropsis sp followed by Chlorella and Thalassiosira sp (1-3×105 cells/ml) i.e. 8 and 7 number of individual/broodstock respectively where as the species attained maturity within 3 days in the treatment fed with Chlorella sp followed by combination of Chlorella and Chaetoceros sp (4 days) and Chlorella and Thalassiosira sp as monospecific diet (4 days each). Mass culture of E. beringi sp. nov. at 100 nos/L was carried out using microalgae, rice bran and baker’s yeast revealed a maximum density 5887 ± 109 nos/L recorded at 30 ‰ within 7 days when fed with mixed diets of Chlorella and Nannochloropsis sp followed by rice bran with baker’s yeast (4586 ± 167 nos/L). Partial replacement of Artemia nauplii with E. beringi sp. nov. (1:1) with highest survival (65 ± 3 %) during early post larval stages of Penaeus indicus revealed its potential to use as live feed in larval rearing. The study highlighted the scope of E. beringi sp. nov. to use as live feed during the larval rearing of brackishwater finfish and shellfishes.

Investigation of biomass production and harvesting of Isochrysis sp. using experimental design methodologies

AbstractBACKGROUNDMicroalgal biodiesel is one of the best promising candidates as an alternative liquid fuel in response to the energy crisis. The timely development of cost‐effective and environmentally friendly culture systems for enhancing microalgae production on a commercial scale is extremely important. In this study, the effects of the process variables temperature, LED light source (blue, white, red), light intensity and aeration rate on biomass production, and the effects of the renewal rate and cycle time on the culture harvest of the marine microalga Isochrysis sp. were investigated using Box–Behnken design (BBD) and central composite design (CCD), respectively.RESULTSThe biomass productivity and lipid content of Isochrysis sp. significantly depended on temperature. Maximum biomass productivity was achieved under white LED light. The optimal conditions for biomass production of Isochrysis sp. with economic cost and energy consumption were a culture temperature of 35 °C, white LED illumination, light intensity 182 μmol m−2 s−1 and an aeration rate of 1.0 L L−1 min−1. A medium renewal rate of 30% and a culture harvest cycle time of three days resulted in the highest biomass productivity for Isochrysis sp. The respective biomass productivities predicted by the models were in good agreement with the results obtained in photobioreactor experiments.CONCLUSIONMajor factors remarkably influenced the culture conditions and biomass harvesting. The results can offer a promising roadmap for the cost‐effective production of biodiesel using Isochrysis sp. © 2021 Society of Chemical Industry

Molecular identification of bacteria isolated from culture medium of the gold-lipped pearl oyster Pinctada maxima larvae

Abstract. Wullur S, Napitupulu H, Wantania LL, Ginting EL, Mamangkey NGF, Smolak R, Ogello E. 2020. Molecular identification of bacteria isolated from culture medium of the gold-lipped pearl oyster Pinctada maxima larvae. Biodiversitas 21: 5291-5297. This study was conducted for the molecular identification of bacteria species isolated from culture medium of the gold-lipped pearl oyster, Pinctada maxima larvae. The pearl oysters were cultured using live-microalgae (Isochrysis sp) and fish waste diet (FWD) as food sources. Bacteria were isolated from the oyster larvae and identified based on the 16S rRNA gene sequence. The isolated bacteria were grown on agar plates and incubated at 37°C for 24 to 48 hours. Representative colonies of the bacteria were selected and cultured for molecular analysis. The 16S rRNA genes of the bacteria were amplified and the sequences were matched with the NCBI GenBank database. Seven different colonies were observed based on morphological characters. Similarity test by conducting the Basic Local Alignment Search Tool (BLAST) in the NCBI GenBank database, using the 16S rRNA gene sequences showed that the seven isolates colonies possess high similarity to five bacteria species i.e. Pseudomonas pachastrellae, Vibrio alginolyticus, Bacillus filamentosus, Bacillus cereus and Idiomarina fontislapidosi belonging to four different genera i.e. Bacillus, Staphylococcus, Vibrio, and Alteromonas.

Lowering the culture medium temperature improves the omega-3 fatty acid production in marine microalga Isochrysis sp. CASA CC 101

Marine microalga Isochrysis sp. contains omega-3 fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Environmental factors play a major role in PUFA biosynthesis. Hence, the study focused to optimize factors such as temperature, pH, and photoperiod by response surface methodology (RSM). RSM results showed that the model is significant (p ≤ 0.05) with a high correlation coefficient (R 2 = 0.908). The optimum conditions showed that maximum biomass (327 mg/L) at the temperature of 30 °C, pH of 7.5 and 16:8 (Light: Dark cycle), whereas the higher amount of DHA (13.3%) and EPA (9.0%) was observed in the conditions of 18 °C, pH of 7.5 and 16:8 (Light: Dark cycle). The biomass content was directly proportional to the temperature whereas DHA content was inversely proportional. It was revealed that the mRNA expression of EPA and DHA specific desaturases (5Des & 4Des) were significantly elevated in low temperature (20 °C) conditions. The results were highly correlated with the fatty acid profile of Isochrysis sp. grown under low temperature (20 °C) conditions which enhanced the EPA and DHA levels. This study suggests that the temperature is the most influencing factor which can be exploited in the industrial application of DHA and EPA production from Isochrysis sp.

Nitrogen repletion favors cellular metabolism and improves eicosapentaenoic acid production in the marine microalga Isochrysis sp. CASA CC 101

Isochrysis sp. is a marine microalga and is a potential source of eicosapentaenoic acid and docosahexaenoic acid, which possess several health benefits. In general, Isochrysis sp. grow well in nitrate-rich culture medium which influences fatty acid biosynthesis; therefore, this study focused on how nitrate influences cellular metabolism in the marine microalga Isochrysis sp. CASA CC 101. Initially, response surface methodology was performed to optimize the level of major nutrients: nitrate and phosphate. The results showed that Isochrysis sp. when grown with nitrate at a concentration of 593 mg.L−1 produced higher eicosapentaenoic acid (7.3 mg.L1), whereas Isochrysis sp. when grown with higher concentration of phosphate did not produce higher levels of eicosapentaenoic acid. The influence of nitrate on cellular metabolism was further confirmed by culturing Isochrysis sp. at higher nitrate conditions. The cellular metabolic activity was analyzed by reactive oxygen species staining assay and the results showed that the cells exhibited reduced oxidative stress with lower green fluorescence under nitrate-repleted conditions. Furthermore, live/dead staining and cell viability assay revealed that live cell population was higher in nitrate-repleted conditions. Nile red and scanning electron microscopy analysis revealed that the cell size and intracellular lipid droplets of microalgal cells grown under nitrate-repleted cells were low, whereas the cell size and intracellular lipid droplets of the microalgal cells grown under nitrogen-depleted conditions were high. Further, the fatty acid profile of Isochrysis sp. grown under nitrogen-repleted conditions showed an increased eicosapentaenoic acid (22.52 mg.g−1 biomass). The mRNA expression of polyunsaturated fatty acid biosynthetic genes such as Δ5-desaturase (Δ5Des) was significantly elevated in nitrate-repleted conditions, whereas the expression of the Δ6-desaturase (Δ6Des) remained unaltered under all the conditions. This is the first study to demonstrate the correlation between nitrate repletion and cellular metabolic activity in terms of eicosapentaenoic acid production in Isochrysis sp. CASA CC 101.

A Chemically Safe Way to Produce Insect Biomass for Possible Application in Feed and Food Production.

Black soldier fly (Hermetia illucens, HI, Diptera, Stratiomydae) has great potential as a food and feed ingredient in the European Union (EU). The production of insects as livestock feed or as food ingredients requires strict monitoring of the content of potentially toxic elements (PTEs) in the growth substrate, to meet the security requirements. This study aims to investigate the presence of PTEs, like cadmium, lead, mercury, arsenic, and nickel, in HI prepupae and in their growth substrates based on coffee roasting by-product and microalgae Schizochytrium sp. and Isochrysis sp. Analyses were carried out via graphite furnace atomic absorption spectrophotometry for Cd, Pb, Ni, and As, and via Direct Mercury Analyzer for Hg. All element concentrations found in growth substrates were below the legal limit of undesirable substances in animal feed (2002/32/EC). Elements concentrations in HI prepupae were in the range (mg kg−1 wet weight) of 0.072 to 0.084 for Cd, 0.018 to 0.026 for Pb, 0.010 to 0.032 for Hg, 0.036 to 0.047 for As, and 0.18 to 0.76 for Ni. Even if HI prepupae accumulated Cd, Pb, and Hg, our results indicated that the risk of exposure to PTEs from HI prepupae consumption is relatively low and in compliance with EU regulations.

Stability of Li-LSX Zeolite in the Catalytic Pyrolysis of Non-Treated and Acid Pre-Treated Isochrysis sp. Microalgae

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.

Comparison of fatty acid composition and positional distribution of microalgae triacylglycerols for human milk fat substitutes

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.

Effect of Li-LSX-zeolite on the in-situ catalytic deoxygenation and denitrogenation of Isochrysis sp. microalgae pyrolysis vapours

In this work, we report for the first time the use of Li-LSX-zeolite as catalyst for the catalytic pyrolysis of biomass (Isochrysis sp. Microalgae). Li-LSX-zeolite showed a good catalytic performance, principally for bio-oil denitrogenation (mainly in form of NH3), and good activity for olefins and aromatics production. At 500 °C, 11.8% aromatics and 23.1% aliphatics were produced. The increase of temperature led to transfer of C to the gas phase, coke formation on the catalyst surface and decrease in N-compounds in the bio-oil. The increase of the catalyst to biomass ratio from 0 to 3:1 resulted in the aromatics being five-fold those non-catalytically obtained and in a higher cracking power that reduced the bio-oil to 23% at expenses of olefins rich gas. However, a linear correlation between coke formation and aromatic yield was observed as the catalyst to microalgae ratio was increased. Therefore, the experimental results indicate that Li-LSX-zeolite could be used as catalyst for in-situ denitrogenation of microalgae bio-oil and for enhancing aliphatics and aromatics formation to be blend in gasoline and diesel and olefins in gas phase.

Functional characterization and substrate specificity analysis of Δ6-desaturase from marine microalga Isochrysis sp.

To express a Δ6-desaturase gene and produce gamma-linolenic acid (GLA) and stearidonic acid (SDA) in prokaryotic expression system (Escherichia coli), and analyze its substrate specificity in the omega-3 fatty acid biosynthetic pathway. Full-length ORF (1448bp) of Δ6Des-Iso was isolated from Isochrysis sp. and characterized using multiple sequence alignment, phylogenetic analysis, transmembrane domain, and protein tertiary structure. Δ6Des-Iso is a front-end desaturase consisting of three conserved histidine domains and a cytochrome b5 domain. Δ6Des-Iso was cloned and expressed in E. coli with the production of GLA and SDA. Recombinant E. coli utilized 27 and 8% of exogenously supplied alpha-linolenic acid (ALA) and linoleic acid (LA) to produce 6.3% of SDA and 2.3% of GLA, respectively, suggesting that isolated Δ6Des-Iso is specific to the omega-3 pathway. For the first time production of GLA and SDA in a prokaryotic system was achieved.

Screening of marine microalgae strains from Moroccan coasts for biodiesel production

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.

BIOSYNTHESIS OF SILVER NANOPARTICLES USING MARINE MICROALGAE ISOCHRYSIS sp.

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 Isochrysis sp. 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.

Decolorization improves the fuel properties of algal biodiesel from Isochrysis sp.

Results from the comprehensive fuel testing according to American Society for Testing and Materials International (ASTM) standards of an alkenone-free and decolorized biodiesel produced from the industrially grown marine microalgae Isochrysis sp. are presented. Fatty acid methyl ester (FAME) profiles of the non-decolorized and subsequently decolorized biodiesel fuels were nearly identical, yet the fuel properties were remarkably different. Significant positive impacts on the cetane number, kinematic viscosity, and lubricity were observed, indicating a potential deleterious effect of pigments like chlorophylls and pheophytins on these fuel properties. The decolorization process using montmorillonite K10 gave on average 90% mass recovery, and allowed for an otherwise unobtainable cloud point determination. Oxidative stability of the decolorized Isochrysis biodiesel remained well below the minimum prescribed in biodiesel standards due to elevated content of highly polyunsaturated fatty acids, however other values were in the range of those prescribed in the ASTM standards. Overall, decolorization improved the fuel properties of biodiesel from Isochrysis and may provide a path toward improved biodiesel fuels from other algal species.

Copper and Cadmium Toxicity to Marine Phytoplankton, &lt;i&gt;Chaetoceros gracilis&lt;/i&gt; and &lt;i&gt;Isochrysis&lt;/i&gt; sp.

In Copper (Cu) based antifouling (AF) paints Cu was largely used as booster biocide after organotin was banned. Cu is micronutrient which is important in photosynthesis process because Cu is an essential metal as component of enzyme and electron transport chain. But in certain dosage, Cu could be toxic to marine organism. Chaetoceros gracilis and Isochrysis sp. are dominant microalgae in aquatic ecosystem. In this study the effect of Cu and Cadmium (Cd) on two marine microalgae, C. gracilis and Isochrysis sp. were compared. Toxicity test was based on American Standard for Testing Material (ASTM). IC50-96 h of Cd as reference toxicant was 2,370 mg.L-1 for C. gracilis and 490 mg.L-1 for Isochrysis sp. IC50-96 h of Cu to growth of C. gracilis was 63.75 mg.L-1 and Isochrysis sp. was 31.80 mg.L-1. Both Cd and Cu were inhibited growth of microalgae. Based on IC50-96 h value, it could be concluded that Cu was more toxic than Cd. Toxicity of Cu was 37 times stronger than Cd for C. gracilis and 15 times for Isochrysis sp. It was estimated that at concentration 10 mg.L-1 Cu does not show observable effect (NOEC) to C. gracilis and 5 mg.L-1 to Isochrysis sp. The lowest observable effect of Cu (LOEC) to C. gracilis was at concentration 17 mg.L-1 and 10 mg.L-1 for Isochrysis sp.

Cloning and molecular characterization of a delta-6 fatty acid desaturase gene from Isochrysis sp. CCMM5001

The cDNA of the delta-6 (Delta 6) fatty acid desaturase gene IsFAD6 was isolated from the marine microalga Isochrysis sp. CCMM5001. Sequence analysis indicated that the total length of IsFAD6 is 2767 bp, and the gene contains a 1407-bp open reading frame, a 406-bp 5' untranslated region (UTR), and a 954-bp 3' UTR with a typical polyA tail. The gene encodes a protein with 469 amino acids, with a molecular weight of 52.9 kDa and an isoelectric point of 8.6. IsFAD6 contains three conserved histidine motifs and a cytochrome b5 domain. Real-time PCR analysis showed that the expression levels of IsFAD6 were significantly upregulated under diverse abiotic stresses, including low temperature (15 and 25 A degrees C), high salinity (62aEuro degrees), and high nitrogen deficiency (220 mu mol L-1 sodium nitrate), compared with those under control conditions (20 A degrees C, 31aEuro degrees salinity, and 880 mu mol L-1 sodium nitrate in the f/2 medium). The IsFAD6 transcript levels minimally increased under high salinity (93aEuro degrees) and excess sodium nitrate (1760 mu mol L-1). Our findings provided an understanding of IsFAD6 responses to temperature, salinity, and nitrate stresses at the transcriptional level. These results indicated that IsFAD6 cloned from Isochrysis sp. CCMM5001 is involved in acclimation to temperature, salt, and nitrogen stresses. The heterologous expression of IsFAD6 in Saccharomyces cerevisiae futher indicated that IsFAD6 could utilize endogenous substrates to synthesize gamma-linolenic acid (18:3(Delta 6,9,12)) and stearidonic acid (18:4(Delta 6,9,12,15)), which are involved in acclimation to adverse conditions.