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BackgroundThis batch study deals with the relation between lipid as well as triglyceride contents in Nannochloropsis salina and variation in culture conditions such as nitrogen concentration and temperature.ResultsThe tested parameters caused reduction in growth expressed as cell count, optical density and dry weight, as well strongly involved in lipids and triglycerides accumulation and significantly affected the lipid productivity. At the beginning of the work, the concentration of nitrogen in the medium was reduced to three quarter, half and quarter of the original f2 medium while the temperature kept constant. After that, the optimal nitrogen concentration (quarter of the original media) giving high lipid yield was tested with different temperature degrees from 15 to 35°C with five degree intervals. Although the growth was insignificantly influenced, a considerable increase in lipid and triglyceride (56.1 and 15.1% of dry weight respectively) was observed when the concentration of nitrogen in the medium was reduced to the quarter. Moreover, 59.3% lipid and 17.1% triglyceride on the basis of dry weight were obtained by the combination of 25% nitrogen concentration and 30°C. Simple regressions recommended that the interaction effect of nitrogen limitation and temperature on lipid and triglyceride accumulation was not as fundamental as for nitrogen limitation stress.ConclusionThe degree of nitrogen availability in the combination of temperature effect has been identified as the critical determinant for the maximal production of lipid in N. salina. Nevertheless, major advances in this field can be considered by studying more stresses techniques and genetic strategies.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0085-7) contains supplementary material, which is available to authorized users.

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The purpose of this study was to test the nematicidal activity of extracts of two marine algae (Colpomenia sinuosa and Corallina mediterranea) and their synthesized silver nanoparticles against root-knot nematodes (Meloidogyne incognita) that infest tomato plants. Scanning electron microscopy (SEM) revealed that nanoparticles had aggregated into anisotropic Ag particles, and transmission electron microscopy (TEM) revealed that the particle sizes were less than 40 nm. Fourier Transform Infrared Spectroscopy (FT-IR) analysis revealed that the obtained nanoparticles had a sharp absorbance between 440 and 4000 cm−1, with 13 distinct peaks ranging from 474 to 3915 cm−1. Methylene chloride extracts and nanoparticles synthesized from both algae species were used to treat M. incognita. C. sinuosa nanoparticles had the highest nematicidal activity of any treatment. Furthermore, and in contrast to other treatments, C. sinuosa nanoparticles reduced the number of nematode galls, egg-masses per root, and eggs/egg mass, while also improving plant growth parameters. C. sinuosa's methylene chloride extract was more active than C. mediterranea's, and the most effective eluent of this solvent was hexane: methylene chloride: ethyl acetate (1: 0.5: 0.5, v/v/v). When applied to M. incognita, the third fraction of this eluent was the most effective, resulting in 87.5% mortality after 12 h and 100% mortality after 24 and 72 h of exposure. The presence of seven bioactive constituents was discovered during the analysis of this fraction. In conclusion, the silver nanoparticles synthesized from C. sinuosa could be used as alternative chemical nematicides.

Background Seaweeds harbour a wide array of bioactive compounds shown to be effective in support of sustainable agricultural practices. The green seaweed Chaetomorpha antennina found in abundance in coastal areas of India has been reported with various bioactivities. Owing to the requirement of alternative and economical natural pest control method to be applied in sustainable agronomic strategies, the current study attempts to evaluate the efficacy of chemical toxins from C. antennina, as insecticidal agents, by inspecting their effects on the physiology, biochemistry, immune system, and histology of one of the most important insect pests of agricultural crops in the Asian tropics, the polyphagous lepidopteran Spodoptera litura. Results The active fraction 5 isolated from C. antennina using methanol extraction produced significant mortality rates of S. litura among all the other fractions obtained. GC–MS analysis revealed the presence of various pesticide compounds. The toxin compounds (active fraction 5) were found to negatively influence the pest’s immune system performance at sub-lethal concentrations (LC50 38.73and LC90 53.60 ppm), affecting insect development, reducing the haemocyte count (69.24%) and reduced the activity of major defence enzyme phenoloxidase decreased post-treatments. Digestive phosphatase enzymes, acid phosphatase, ACP, alkaline phosphatase, ALP, and ATPase were demodulated by 37.5, 39, and 23.9% compared with untreated. Increase in detoxification enzymes coupled with mid-gut collapse are indicative of the toxicity of the compounds. Earthworms exposed to seaweed compounds displayed no debarring effects. Conclusion Extracted seaweed compounds produced significant lethal effect on the insect larvae, affecting the immune as well as digestive systems of the pest. However, no such toxicity was observed in earthworms treated with the seaweed fraction supporting their environmentally benign nature. Since the insect immune system is responsible for the development of resurgence against pesticides, suppression of immunological activities by seaweed toxins indicate the long-term applicability of these compounds as prospective pesticides. The results support the potential of chemicals from C. antennina for biopesticide development to manage economically important agricultural pests.

This study discusses the perspectives regarding the green alga Dunaliella salina Toed for biodiesel manufacturing purposes. The alga was cultivated under controlled lab conditions. Biomass concentration at early stationary grown microalga was 2.6 mg/L dry weight, while the algal oil was about 27.1% of the biomass. Algal oil was esterified and analyzed using GLC technique. Fourteen fatty acid methyl esters were identified. The amount of saturated and unsaturated fatty ester fractions was 35% and 65% respectively. The physicochemical properties of fatty acids comprising biodiesel were discussed. However, culture optimization coupled with genetic improvement will definitely represent contributions to bring about innovation in oil hyper-producing D. salina that will ultimately meet with success.

BackgroundPlant-parasitic nematodes are one of the major constraints to soybean production around the world. Plant-parasitic nematodes cause an estimated $78 billion in annual crop losses worldwide, with a 10–15% crop yield loss on average. Consequently, finding and applying sustainable methods to control diseases associated with soybean is currently in serious need.MethodsIn this study, we isolated, purified, characterized, and identified a novel cyanobacterial strain Oscillatoria sp. (blue-green alga). Based on its microscopic examination and 16S rRNA gene sequence, the aqueous and methanolic extracts of Oscillatoria were used to test their nematicidal activity against Meloidogyne incognita hatchability of eggs after 72 h of exposure time and juvenile mortality percentage in vitro after 24, 48, and 72 h of exposure time and reduction percentage of galls, eggmass, female number/root, and juveniles/250 soil. Also, the efficacy of the extract on improving the plant growth parameter and chlorophyll content under greenhouse conditions on soybean plant cv. Giza 111 was tested. Finally, the expression of PR-1, PR-2, PR-5, and PR15 (encoding enzymes) genes contributing to plant defense in the case of M. incognita invasion was studied and treated with Oscillatoria extract.ResultsThe aqueous and methanolic extracts of Oscillatoria sp. had nematicidal activity against M. incognita. The percentage of mortality and egg hatching of M. incognita were significantly increased with the increase of time exposure to Oscillatoria extract 96.7, 97, and 98 larvae mortality % with S concentration after 24, 48, and 72 h of exposure time. The aqueous extract significantly increased the percentage of Root-Knot nematodes (RKN) of egg hatching, compared with Oxamyl and methanol extract at 96.7 and 97% after 72 h and 1 week, respectively. With the same concentration in the laboratory experiment. Furthermore, water extracts significantly reduced the number of galls in soybean root, egg masses, and female/root by 84.1, 87.5, and 92.2%, respectively, as well as the percentage of J2s/250 g soil by 93.7%. Root, shoot lengths, dry weight, number of pods/plant, and chlorophyll content of soybean treated with Oscillatoria water extract were significantly higher than the control increasing by 70.3, 94.1, 95.5, and 2.02%, respectively. The plant defense system's gene expression was tracked using four important pathogenesis-related genes, PR-1, PR-2, PR-5, and PR15, which encode enzymes involved in plant defense.ConclusionsOscillatoria extract is a potential nematicide against root-knot nematode invasion in soybean.

The uptake of fast orange dye by the red seaweed Laurencia papillosa has been demonstrated in order to explore its potential use as low-cost adsorbent. The adsorption kinetics of fast orange dye on the alga with respect to initial dye concentration, contact time, particle size and pH were investigated. The dye removal percentage increased from 25.92 to 67.08% and the equilibrium states were attained at almost 60 min within the experimental concentration range. The adsorption kinetic was analyzed using pseudo-first-order and pseudo-second-order models. The pseudo-second-order model was more appropriate to describe the sorption kinetics based on the relatively high values of the linear squared regression correlation coefficient. The nature of the possible adsorbent and fast orange interactions was examined by the Fourier transform infrared technique. This technique confirmed that hydroxyl, carboxyl, amine, sulfonyl, carbonyl and alkyl groups are responsible for the dye binding process. Significant increase in dye adsorption was observed with the decrease in sorbent particle size coupled with its large surface area. Maximum removal efficiency was determined to be 65.7% at a solution pH of 5. However, Laurencia papillosa proved to be a promising material for removing fast orange dye from aqueous solutions.