Marine Microalga Nannochloropsis Research Articles

Role of Nannochloropsis Oculata supplement in improving performance, antioxidant status, blood metabolites, and egg quality of laying hens under hot environmental conditions

The increase in environmental temperature led to economic losses in the poultry industry, urging the use of feed supplements to mitigate the negative effects on chick's welfare and performance. Therefore, this study aimed to examine the effects of marine microalgae (Nannochloropsis Oculata, N. Oculata) additive on commercial Brown Lohmann laying hen's performance, blood metabolites, and antioxidant status under hot environmental conditions. One hundred and eighty birds (34 weeks old with an initial body weight of 1885 ± 23.5 g) were used till 47 weeks. The birds were divided into three equal groups (birds in each group were distributed into four equal replicates 15 hens/ replicate). The 1st group was the control (CON) and was fed the basal diet, while the 2nd (TR1) and 3rd (TR2) groups were fed the basal diet supplemented with 0.5 and 1.0% of N. Oculata, respectively. The results showed that total protein and globulin concentrations increased (P < 0.05) in treated groups compared with the control group, whereas, albumin concentration increased (P < 0.05) in TR2 compared to the control group. The concentration of ALT and AST decreased in hens fed N. Oculata. Supplementing with N. Oculata reduced serum cholesterol and creatinine concentrations, while glucose concentration increased (P < 0.05) in the treated groups compared to the control group. Serum calcium, total antioxidant capacity (TAC), Triiodothyronine (T3), and progesterone increased (P < 0.05) in hens fed N. Oculata. N. Oculata supplement improved production performance through a positive effect on egg number, egg weight, egg mass, feed conversion ratio, and mortality rate. In addition, the overall mean of shell thickness increased (P < 0.05) in hens fed N. Oculata. It can be concluded that the supplementation of 1.0% N. Oculata to the laying hens' diet enhanced productive performance, serum constituents, and antioxidant status under hot environmental conditions.

Cu2O/Biochar-Styrene acrylic double layer composite coatings modified by NaCl: Special surface and antifouling performance

In order to pursue optimize antifouling performance and protect the metal substrate from direct contact with external environment, the sodium chloride (NaCl) modified cuprous oxide (Cu2O)/Biochar (BC)/styrene-acrylic (SA)-SA double-layer coatings with the effective and controllable release rate of Cu2+ were prepared. The NaCl particles were dispersed and dissolved in the Cu2O/BC/SA layer (the functional layer) as the pore-forming agent, which can increase the contact between Cu2O/BC and external environment in order to control the release rate of Cu2+ of coatings. A large capacity photobioreactor was designed to conduct adhesion tests of marine microalgae Nannochloropsis oceanica (N. oceanica) and fresh Chlorella vulgaris (C. vulgaris) on the coatings, aiming to evaluate the antifouling performance. Results show that the Cu2O/BC/SA-SA coating modified with 3 wt% NaCl possesses the best antifouling property, which is 63.7 % higher than that of unmodified coating and 92.8 % higher than that of pure SA membrane.

Effects of microalgae diets on growth, proximate, and fatty acid composition of black mussel, Mytilus galloprovincialis

AbstractThis study evaluates the growth, proximate, and fatty acid composition of black mussel, Mytilus galloprovincialis fed four marine microalgae (Pavlova lutheri, Nannochloropsis oculata, Diacronema vlkianum and Rhinomonas reticulata) diets for 21 days. Black mussel is a common bivalve species that has been recognized as important for marine aquaculture with increasing production in the last two decades. The mussel group fed N. oculata showed a significantly lower survival rate than the other groups (p &lt; 0.05). Shell height, length, and width of mussels were measured. The height and length of the mussel group fed N. oculata were statistically higher than other experimental groups (p &lt; 0.05). Shell width did not show any significant differences among groups (p &gt; 0.05). The microalgae N. oculata showed the highest protein content whereas P. lutheri had the highest crude lipid content among dietary treatments. The group fed P. lutheri showed significantly higher protein, lipid, and ash contents among experimental groups (p &lt; 0.05). The D. vlkianum diet enhanced the highest docosahexaenoic acid level in black mussels. Black mussel fed P. lutheri showed the highest eicosapentaenoic acid and polyunsaturated fatty acid levels. Arachidonic acid was found to be similar among experimental groups. In our study, P. lutheri and D. vlkianum had outstanding results on survival, growth, and essential fatty acid accumulation in mussel culture.

Engineering whiting events in culture: A microalgae-driven calcium carbonate and biomass production process at high pH and alkalinity with the marine microalga Nannochloropsis oceanica IMET1

The impact of whiting events on global inorganic carbon cycle and climate change is debatable at the current ocean pH. This work engineered whiting events in a high pH, high alkalinity microalgal culture for carbon dioxide capture and storage. When growing the marine microalga Nannochloropsis oceanica IMET1 in photobioreactors, culture alkalinity more than doubled, increasing from 72.5 mg L-1 to a maximum level of 159.6 mg L-1. At the same time, culture pH increased from 7.9 to 10.1 with concomitant calcium carbonate production. X-ray diffraction analysis revealed the precipitated calcium carbonate was primarily monohydrocalcite. The lab culture was scaled up to a 340-L bioreactor, in which Nannochloropsis ash-free dry weight productivities ranged from 25.1 to 51.4 g m-2 d-1 and a maximum monohydrocalcite productivity of 133.4 g m2 d-1 was recorded. In this system, Nannochloropsis biomass contained about 23.9 % lipids and the eicosapentaenoic acid content was about 1.8 %. Together, these results suggest the microalgae-driven calcium carbonate and biomass production process efficiently captures and stores atmospheric carbon dioxide in the form of calcium carbonate while producing valuable bioproducts. Study of the bacterial communities associated with the Nannochloropsis culture identified four dominant species Maricaulis maris, Marinisubtilis pacificus, Gracilimonas sp., and an uncultured bacterium in the OD1 phylum with interesting features that warrant further investigation.

Direct extracellular electron transfer for high electricity production by a new type of marine microalgae Nannochloropsis sp. HDY2

A growing number of autotrophic microalgae have been found to have extracellular electron transfer (EET) capabilities. However, the mechanism and function of EET pathway in microalgae have not thoroughly investigated. This study presents evidence of direct extracellular electron transfer (DEET) for impressive electricity production by a new type of marine microalgae Nannochloropsis sp. HDY2 in the single and double-chamber photosynthetic microbial fuel cells (PFMCs). The electricity generation of Nannochloropsis sp. is strongly inhibited by photosynthetic inhibitors, suggesting that electrons involved in the extracellular electron transfer (EET) of Nannochloropsis sp. are derived from photosynthesis. The results of dialysis bag and supernatant experiments suggest that Nannochloropsis sp. produce electricity by DEET. The lack of typical redox peaks in cyclic voltammetry (CV) analysis and the appearance of extracellular filamentous component (EFC) around cells support this finding. Under high light conditions, the chlorophyll a and carotenoid content of Nannochloropsis sp. rapidly decreased while the fatty acid synthesis and electricity generation increased, suggesting that the DEET pathway play an active role in the resistance to photooxidation of Nannochloropsis sp. This study provides the first evidence that Nannochloropsis has the capability of performing EET and sheds new light on the positive role of DEET on the environmental adaptation of Nannochloropsis.

Lipid Enhancement in Oleaginous Nannochloropsis sp. under Nitrate Limitation for Future Bioenergy Production

Microalgae possess high oil content, exhibit rapid growth rates and biomass productivity, and leave a minimal environmental footprint, making them highly attractive for biofuel applications. Consequently, this present study is aimed at evaluating the impact of nitrogen starvation on the marine microalgae Nannochloropsis sp. to enhance lipid accumulation. The microalga culture was grown under an irradiance of 120 μmol photon m-2 s-1, temperature 25 ± 1 °C, continuous air-CO2, and with different concentrations of sodium nitrites over a 14-day cultivation period. From the results, it was found that the growth of the strain decreased under limited nitrogen conditions. After harvesting, the cells in the supernatant were regenerated by cultivating in double concentration of media. The results showed that on the 12th day, the highest lipid content was achieved, reaching 68.0 ± 2.3 wt.% of the dry weight under nitrogen limitation. The composition of the obtained lipid consisted of 18.0 wt.% saturated fatty acids, 72.38 wt.% monounsaturated fatty acids, and 8.95 wt.% polyunsaturated fatty acids. The lipid composition was dominated by monounsaturated oleic acid ( 70.97 ± 4.6 wt.%), saturated palmitic acid ( 13.68 ± 1.0 wt.%), and polyunsaturated linoleic acid ( 8.41 ± 0.4 wt.%). The findings of this study demonstrated that limiting nitrogen availability enhanced lipid accumulation in Nannochloropsis sp. Despite experiencing inhibited growth, this microalga species shows great potential for the large-scale cultivation of lipids and essential fatty acids. These results contribute to understanding the relationship between nitrogen availability and lipid metabolism in microalgae, providing valuable insights for optimizing lipid production in the context of biofuel and biotechnology applications.

Polar Lipids of Marine Microalgae Nannochloropsis oceanica and Chlorococcum amblystomatis Mitigate the LPS-Induced Pro-Inflammatory Response in Macrophages.

Microalgae are recognized as a relevant source of bioactive compounds. Among these bioactive products, lipids, mainly glycolipids, have been shown to present immunomodulatory properties with the potential to mitigate chronic inflammation. This study aimed to evaluate the anti-inflammatory effect of polar lipids isolated from Nannochloropsis oceanica and Chlorococcum amblystomatis. Three fractions enriched in (1) digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol (SQDG), (2) monogalactosyldiacylglycerol (MGDG), and (3) diacylglyceryl-trimethylhomoserine (DGTS) and phospholipids (PL) were obtained from the total lipid extracts (TE) of N. oceanica and C. amblystomatis, and their anti-inflammatory effect was assessed by analyzing their capacity to counteract nitric oxide (NO) production and transcription of pro-inflammatory genes Nos2, Ptgs2, Tnfa, and Il1b in lipopolysaccharide (LPS)-activated macrophages. For both microalgae, TE and Fractions 1 and 3 strongly inhibited NO production, although to different extents. A strong reduction in the LPS-induced transcription of Nos2, Ptgs2, Tnfa, and Il1b was observed for N. oceanica and C. amblystomatis lipids. The most active fractions were the DGTS-and-PL-enriched fraction from N. oceanica and the DGDG-and-SQDG-enriched fraction from C. amblystomatis. Our results reveal that microalgae lipids have strong anti-inflammatory capacity and may be explored as functional ingredients or nutraceuticals, offering a natural solution to tackle chronic inflammation-associated diseases.

Simultaneous production of bio-crude bio-oil via hydrothermal liquefaction and carotenoids via supercritical extraction from Nannochloropsis oceanica and recycling effluent to establish circular processes

Commercial production of microalgae biofuel is not economically feasible since it cannot compete with the price of fossil fuels. Algal biofuel could be cost-effective if high-value co-products are produced from microalgal biomass before it is converted into biofuel. Thus, this research aims to demonstrate a circular biorefinery process of producing bio-crude bio-oil as well as high-value products like carotenoids from a marine microalga Nannochloropsis oceanica. The microalga was cultivated in raceway ponds over the years with the highest biomass productivity of 30–40 g m−2 day−1 recorded in October and November of 2021, but it reduced in extremely high summer temperatures and low temperatures in winter of Delhi NCR, India. The annual average biomass productivity of 19.13 g m−2 day−1 was recorded, which is equivalent to 69825 kg ha−1 year−1. The algal biomass was processed for high-value carotenoids using a green process, i.e. supercritical carbon dioxide extraction. Carotenoid yield of 252 μg/g of biomass was obtained after optimizing temperature and pressure in the supercritical extraction process. The spent biomass after carotenoid extraction was used to produce bio-crude bio-oil using hydrothermal liquefaction. There was no significant difference between bio-crude oil yield and properties after carotenoid extraction and direct biomass use. A bioeconomic methodology for closing the circular loop involving recycling the effluent generated during hydrothermal liquefaction to re-cultivate the microalgae is demonstrated. This study highlights the potential of green technology, circular bioeconomy, and biorefinery practices in developing sustainable and environmentally friendly solutions for the chemical and energy sectors.

LASSO Regression with Multiple Imputations for the Selection of Key Variables Affecting the Fatty Acid Profile of Nannochloropsis oculata.

The marine microalga Nannochloropsis oculata has garnered significant interest as a potential source of lipids, both for biofuel and nutrition, containing significant amounts of C16:0, C16:1, and C20:5, n-3 (EPA) fatty acids (FA). Growth parameters such as temperature, pH, light intensity, and nutrient availability play a crucial role in the fatty acid profile of microalgae, with N. oculata being no exception. This study aims to identify key variables for the FA profile of N. oculata grown autotrophically. To that end, the most relevant literature data were gathered and combined with our previous work as well as with novel experimental data, with 121 observations in total. The examined variables were the percentages of C14:0, C16:0, C16:1, C18:1, C18:2, and C20:5, n-3 in total FAs, their respective ratios to C16:0, and the respective content of biomass in those fatty acids in terms of ash free dry weight. Many potential predictor variables were collected, while dummy variables were introduced to account for bias in the measured variables originating from different authors as well as for other parameters. The method of multiple imputations was chosen to handle missing data, with limits based on the literature and model-based estimation, such as using the software PHREEQC and residual modelling for the estimation of pH. To eliminate unimportant predictor variables, LASSO (Least Absolute Shrinkage and Selection Operator) regression analysis with a novel definition of optimal lambda was employed. LASSO regression identified the most relevant predictors while minimizing the risk of overfitting the model. Subsequently, stepwise linear regression with interaction terms was used to further study the effects of the selected predictors. After two rounds of regression, sparse refined models were acquired, and their coefficients were evaluated based on significance. Our analysis confirms well-known effects, such as that of temperature, and it uncovers novel unreported effects of aeration, calcium, magnesium, and manganese. Of special interest is the negative effect of aeration on polyunsaturated fatty acids (PUFAs), which is possibly related to the enzymatic kinetics of fatty acid desaturation under increased oxygen concentration. These findings contribute to the optimization of the fatty acid profile of N. oculata for different purposes, such as production of, high in PUFAs, food or feed, or production of, high in saturated and monounsaturated FA methyl esters (FAME), biofuels.

Extrusion processing improves rainbow trout digestibility of microalgal Nannochloropsis oculata co-product biomass for more sustainable aquaculture diets

Aquaculture feeds include fishmeal (FM) and fish oil (FO), derived from wild-caught marine fish such as anchovy and sardines, and pose ecological, food security, and economic drawbacks for sustainable aquaculture, the world's fastest-growing agricultural sector. Protein-rich microalgal co-product is a promising alternative to unsustainably sourced fishmeal in aquaculture diets. Microalgal co-product is a defatted biomass left over after extracting omega-3-rich oil for human nutraceuticals and crude oil for fuels. In this study, we report the first evaluations of nutritive values and digestibility of raw, extrusion- and enzymatic-processed co-product of the marine microalga Nannochloropsis oculata (N. oculata co-product). Results allowed us to evaluate the feasibility of using processed biomass in aquafeed for rainbow trout (Oncorhynchus mykiss), an important model for all salmonid aquaculture. Extrusion processing temperature (90 °C vs 127 °C) influenced the nutritional value of N. oculata. Protein and energy levels were significantly higher in co-product from both extrusion temperature treatments than in non-extruded raw co-product. Essential amino acid levels did not differ between extrusion temperatures, except that methionine was significantly lower in coproduct from 127 °C extrusion processing than from 90 °C extrusion processing. The protein level in extrusion processed co-product was not significantly influenced by pre-cooking. We detected the highest digestibility of crude protein, energy, most of the amino acids, and omega 3 polyunsaturated fatty acids (n3 PUFA) in extruded (90 °C) N. oculata co-product ingredient. Nutrient digestibility of enzymatic processed N. oculata co-product were mostly the same as extrusion processing or lower for certain nutrients. Overall, extrusion processing of N. oculata at 90 °C provided the best outcome for digestible protein, and yielded an excellent source of digestible protein, amino acids, and long chain omega-3 profile for rainbow trout and which could be an alternative to replace fishmeal in rainbow trout diets.

Remodeling of the 3D chromatin architecture in the marine microalga Nannochloropsis oceanica during lipid accumulation

BackgroundGenomic three-dimensional (3D) spatial organization plays a key role in shaping gene expression and associated chromatin modification, and it is highly sensitive to environmental stress conditions. In microalgae, exposure to nitrogen stress can drive lipid accumulation, yet the associated functional alterations in the spatial organization of the microalgal genome have yet to be effectively characterized.ResultsAccordingly, the present study employed RNA-seq, Hi-C, and ChIP-seq approaches to explore the relationship between 3D chromosomal architecture and gene expression during lipid accumulation in the marine microalga Nannochloropsis oceanica in response to nitrogen deprivation (ND). These analyses revealed that ND resulted in various changes in chromosomal organization, including A/B compartment transitions, topologically associating domain (TAD) shifts, and the disruption of short-range interactions. Significantly higher levels of gene expression were evident in A compartments and TAD boundary regions relative to B compartments and TAD interior regions, consistent with observed histone modification enrichment in these areas. ND-induced differentially expressed genes (DEGs) were notably enriched in altered TAD-associated regions and regions exhibiting differential genomic contact. These DEGs were subjected to Gene Ontology (GO) term analyses that indicated they were enriched in the ‘fatty acid metabolism’, ‘response to stress’, ‘carbon fixation’ and ‘photosynthesis’ functional categories, in line with the ND treatment conditions used to conduct this study. These data indicate that Nannochloropsis cells exhibit a clear association between chromatin organization and transcriptional activity under nitrogen stress conditions. Pronounced and extensive histone modifications were evident in response to ND. Observed changes in chromatin architecture were linked to shifts in histone modifications and gene expression.ConclusionsOverall, the reprogramming of many lipid metabolism-associated genes was evident under nitrogen stress conditions with respect to both histone modifications and chromosomal organization. Together these results revealed that higher-order chromatin architecture represents a new layer that can guide efforts to understand the transcriptional regulation of lipid metabolism in nitrogen-deprived microalgae.

Swollen-state preparation of chitosan lactate from moulted shrimp shells and its application for harvesting marine microalgae Nannochloropsis sp.

Chitosan lactate (CSS) has been widely used for academic and industrial applications due to its biocompatibility, biodegradability, and high biological activity. Unlike chitosan, which is generally soluble only in acid solution, CSS can be directly used by dissolving in water. In this study, CSS was prepared from moulted shrimp chitosan at room temperature by a solid-state method. Chitosan was first swollen in a mixture of ethanol and water, making it more susceptible to reacting with lactic acid in the next step. As a result, the prepared CSS had a high solubility (over 99 %) and zeta potential (+ 99.3 mV) and was comparable to the commercial product. The preparation method of CSS is facile and efficient for a large-scale process. In addition, the prepared product exhibited a potential flocculant for harvesting Nannochloropsis sp., a marine microalga widely used as a popular food for larvae. In the best condition, the CSS solution (250 ppm) at pH 10 showed the highest recovery capacity (∼ 90 % after 120 min) for harvesting Nannochloropsis sp. Besides, the harvested microalgal biomass showed excellent regeneration after 6 culture days. This paper's findings suggest a circular economy in aquaculture by producing value-added products from solid wastes, which can minimize the environmental impact and move towards sustainable zero-waste.

Chemical and Biochemical Properties of Marine Algae Ulva lactuca and Nannocholoropsis oculata

Marine algae are considered a source of different bioactive constituents including protein, oil, fiber, vitamins, pigments and dietary minerals. To evaluate the fine chemical and biochemical properties of the marine microalga Nannochloropsis oculata and macroalga Ulva lactuca, the present study was carried out. The cultivated N. oculate and the collected U. lactuca were washed, oven-dried, ground and subjected to analysis of moisture, protein, fats, carbohydrates and ash. In addition, macro and micro-nutrients, amino acids profile, fatty acids methyl ester and pigments were assessed.

Enhancement in lipid productivity of the marine microalga Nannochloropsis sp. SCSIO-45217 through phosphate adjustment strategies

Enhancement in lipid productivity of the marine microalga Nannochloropsis sp. SCSIO-45217 through phosphate adjustment strategies

Identification and Functional Analysis of Acyl-Acyl Carrier Protein Δ9 Desaturase from Nannochloropsis oceanica.

The oleaginous marine microalga Nannochloropsis oceanica strain IMET1 has attracted increasing attention as a promising photosynthetic cell factory due to its unique excellent capacity to accumulate large amounts of triacylglycerols and eicosapentaenoic acid. To complete the genomic annotation for genes in the fatty acid biosynthesis pathway of N. oceanica, we conducted the present study to identify a novel candidate gene encoding the archetypical chloroplast stromal acyl-acyl carrier protein Δ9 desaturase. The full-length cDNA was generated using rapid-amplification of cDNA ends, and the structure of the coding region interrupted by four introns was determined. The RT-qPCR results demonstrated the upregulated transcriptional abundance of this gene under nitrogen starvation condition. Fluorescence localization studies using EGFP-fused protein revealed that the translated protein was localized in chloroplast stroma. The catalytic activity of the translated protein was characterized by inducible expression in Escherichia coli and a mutant yeast strain BY4389, indicating its potential desaturated capacity for palmitoyl-ACP (C16:0-ACP) and stearoyl-ACP (C18:0-ACP). Further functional complementation assay using BY4839 on plate demonstrated that the expressed enzyme restored the biosynthesis of oleic acid. These results support the desaturated activity of the expressed protein in chloroplast stroma to fulfill the biosynthesis and accumulation of monounsaturated fatty acids in N. oceanica strain IMET1.

Potential of enzymatically hydorlysed seaweed products as cost-effective nutrient media for growth and lipid enhancement in the marine microalga Nannochloropsis salina

Enzymatically hydrolysed seaweed products (EHSPs) prepared from the red seaweed, Gracilaria corticata (EHSP-1) and brown seaweed, Stoechospermum marginatum (EHSP-2) contained abundant levels of macro, micro and trace elements necessary to fulfil the nutritional requirement of the microalga Nannochloropsis salina. EHSP-1 had higher levels of N, P, K and Fe in comparison with EHSP-2. The growth performance of N. salina suggests that EHSP-1 was more efficient than EHSP-2. The growth rate of N. salina in EHSP-1 was 1.07 times higher than the control whereas in EHSP-2 the growth rate was 0.58 times lower than the control. The maximum biomass concentration of N. salina was achieved in EHSP-1 and EHSP-2 were 0.37 and 0.21 g l-1 with a biomass productivity of 0.027 and 0.0152 g l-1 d-1 respectively. The results of biochemical analyses also suggest that protein, pigment and lipid yield of N. salina was positively stimulated by EHSP. The findings suggest that the best concentration of EHSP-1 and EHSP-2 to achieve maximum biomass and lipid production of the marine microalga N. salina were 8 and 4% respectively. EHSP-1 enhanced the biomass and lipid production without affecting the nutritional properties of N. salina suggesting its potential applicability in aquaculture, biofuel and other related industrial sectors.Keywords: Cellulase enzyme, Indigenous seaweed resources, Nannochloropsis salina, Nutrient rich media

Therapeutic Potential of Microalgae-Derived Bioactive Metabolites Is Influenced by Different Large-Scale Culture Strategies.

Microalgae have been identified as one of the most promising sources of novel bioactive compounds for biomedical applications, the food industry, and cosmetics. In the last decade, several biotechnological developments have facilitated the identification of a growing number of compounds as well as the study of optimal microalgae culture conditions for the production of biomass enriched in specific molecules of interest. In this study, two common commercial marine microalgae (Nannochloropsis oculata and Porphyridium purpureum) were cultured in standard and nutrient-stressed conditions and the obtained biomass extracts were assessed for their potential to inhibit cancer cell proliferation and migration as well as their antioxidant activity. Results from viability in 2D and 3D cancer cell models showed an enhancement of the antitumour activity of P. purpureum in the 3D model compared to 2D, together with a greater capacity to reduce the migration capacity of cancer cells with the biomass from nutrient-stressed conditions, whereas the antioxidant activity of N. oculata decreased when exposed to nutrient-stressed conditions. To date, this is one of the few studies that proves that controlled changes in large-scale culturing conditions such as nutrient depletion have a relevant impact in the bioactivity of the biomass on cancer cells.

Variations in lipid profile of of the marine microalga Nannochloropsis salina in four different culture media

The present work envisages close monitoring of variations in lipid content and fatty acid profile of the marine microalga Nannochloropsis salina, by growing it in 4 different culture media. Pure cultures of microalga were collected from the marine hatchery complex of the ICAR-Central Marine Fisheries Research Institute, Kochi and cultured in four different media viz., f/2 medium (Guillard, 1975), Miquel’s medium (Miquel, 1892), Walne’s medium (Walne, 1974) and Chu#10 medium (Chu et al., 1942). Standard algal culture conditions viz, salinity 33 ppt, pH 8.0, culture room temperature of 25ºC, light intensity of 1500 lux with a photoperiod of 12 h and Light:Dark cycle of 12 h were maintained. Lipids extracted were subjected to gas chromatography to ascertain their fatty acid profile. Both Miquel’s and f/2 media produced the maximum amount of lipid content (40.2 and 40% respectively). Total saturated fatty acids ranged from 39.17% (Miquel’s medium) to 84.45% (Chu#10). For monounsaturated fatty acids, the highest value was obtained for Miquel’s medium (42.79%) and minimum for Chu#10 (10.55%). Polyunsaturated fatty acids accounted for over 23.50% of the total fatty acids in Walne’s medium followed by Miquel’s (18.04%), f/2(12.76%) and Chu#10(5.00%) media. One way analysis of variance of the data brought to light that the medium composition can influence the fatty acid pattern of microalgae significantly. Keywords: Fish culture, Live feed, Micronutrients, Omega-3, Omega-6

Organic selenium fortification in edible marine microalga Nannochloropsis oceanica CASA CC201 for food and feed applications

Selenium is an essential trace element that performs various biological functions (act as an antioxidant) in our body via a set of proteins called selenoproteins. Organic selenium sources include meat, fish, wheat, etc., which lose their selenium content to a significant extent while cooking and processing. New food sources fortified with organic Selenium are viable to meet selenium deficiency and associated health benefits. In the current study, an edible marine microalga Nannochloropsis oceanica CASA CC201 was developed for over 99 % organic selenium conversion by sequential strain improvement with Sodium selenite over several generations. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis of these cultures has shown that there was a higher accumulation of total intracellular selenium content in the treated samples (565.4 μg Se/g DW) as compared to control (0.108 μg Se/g DW). Organic Se enriched N. ocecanica CASA CC201can withstand as high as 1000 μM sodium selenite without compromising its growth pattern and biomass yield. Collectively, the current study proposes that, an edible marine microalga N. oceanica CASA CC201 biomass with high organic Se content can serve as Selenium fortified food/feed additives with excellent antioxidant properties.

Phytochemical Screening and Evaluation of Antidiabetic Activity of the Marine Microalgae: Nannochloropsis Sp.

Diabetes mellitus is a metabolic disorder and is one of the major challenges on health of people all over the world. The phytochemicals of various marine algae are found to possess antioxidant, anti-inflammatory and anti-diabetic properties. Microalgae are photosynthetic organisms that produce oxygen and are capable of producing beneficial secondary metabolites. The bioactive metabolites like pigments, phenolics, amino acids, polyunsaturated fatty acids etc. produced by them have a positive effect on human health. In the present investigation, the marine microalgae Nannochloropsis sp. was screened for phytochemicals qualitatively and quantitatively. The evaluation of antidiabetic activity was determined against the enzymes such as alpha amylase and alpha glucosidase. The extracts were prepared in five different solvents such as petroleum ether, aqueous, isopropanol, methanol and ethyl acetate. The qualitative analysis for phytochemicals showed the presence of alkaloids, phenols, flavonoids, carbohydrates, proteins, cardiac glycosides, sterols, coumarin and tannins. The maximum total phenolic, flavonoid and sterol content was present in ethyl acetate extract of Nannochloropsis sp. and the values are found to be 42.17 ± 0.12mg GAE/g, 60.23 ± 0.09 mg QE/g, 55.34 ± 0.07 mg cholesterol/g of extract respectively. The ethyl acetate extract showed highest inhibitory effect of 78.52 ±0.56 % (IC50 121.96 µg/ml) on α-amylase and 80.42 ± 0.13 % (IC 50 178.53µg/ml) on α-glucosidase enzyme at a concentration of at 1mg/ml which implies the microalgae possess anti-diabetic property. The results indicate that the phytochemicals present in the microalgae contribute the antidiabetic activity. Hence Nannochloropsis sp. can be applied in pharmaceuticals for the development of antidiabetic drugs which have the benefits over side effects by the use of synthetic drugs.