Alga Nannochloropsis Oculata Research Articles

Biomass Fatty Acid Profile and Fuel Property Prediction of Bagasse Waste Grown Nannochloropsis oculata

The Chrythophyta alga Nannochloropsis oculata was mixotrophically grown in artificial media enriched with acid-prehydrolyzed bagasse waste as a source of organic carbon. The used growth medium was composed of F2 nutrients, sea salt (22.0 g L−1), and bagasse extract dissolved in sterile tap water. All of the determined growth parameters resulted in their maximums, as the alga was fed with 25% F2 growth medium enriched with 10% bagasse extract, while bagasse-extract-free medium engaged the total chlorophyll and carotenes at the expense of dry weight accumulation during the vegetative growth period. On the contrary, the dry weight under induction growth slightly differed among the different employed treatments; however, all the treatments surpassed the control one, and variation was obviously found in the cases of chlorophyll and carotene. A slight increase in oil content (6.19–11.89%) was observed, as the vegetative cells were grown under induction conditions. The fatty acids ranged between C16 and C20, and the proportions of SFA and MUFA increased from a sum of 63.57% to 88.31%, while the PUFA, including linoleic acid, α-linolenic acid, and arachidonic acid, declined from 36.3 to 11.69%. Concerning the fuel properties, the induction-produced oil surpassed the vegetative one.

Cadmium and morphological alterations in the rotifer Philodina cf. roseola (Bdelloidea: Philodinidae) and the worm Aeolosoma hemprichi (Annelida: Aeolosomatidae)

Cadmium is a toxic metal for zooplankton that produces deformations. Therefore, we used two native zooplankton species from Quintana Roo, Mexico, to obtain data regarding cadmium toxicity including the threshold concentration for observable morphological alterations and the percentage of organisms with morphological alterations at the exposure concentrations. We used the rotifer Rotaria sp. and the oligochaeta Aeolosoma hemprichi, both fed with the alga Nannochloropsis oculata. Then, Rotaria sp. and A. hemprichi were exposed to a cadmium concentration range from 0.05 to 10.0 mg L-1. The LC50 for cadmium in Rotaria sp. was 0.7 mg L-1, whereas in A. hemprichi it was 3.38 mg L-1. Cadmium at 0.5 mg L-1 for ≤24 h induced morphological alterations in the lorica of rotifers, foot deformations, and constriction in the middle part of the body. In oligochaetes, damage to the epidermis was noted. The threshold concentration where deformations appeared in rotifer was 0.3 mg L-1 at 24 h and in oligochaeta was 0.5 mg L-1 at 30 min.

Action spectra of oxygen production and chlorophyll a fluorescence in the green microalga Nannochloropsis oculata

The first complete action spectrum of oxygen evolution and chlorophyll a fluorescence was measured for the biofuel candidate alga Nannochloropsis oculata. A novel analytical procedure was used to generate a representative and reproducible action spectrum for microalgal cultures. The action spectrum was measured at 14 discrete wavelengths across the visible spectrum, at an equivalent photon flux density of 60μmolphotonsm−2s−1. Blue light (∼414nm) was absorbed more efficiently and directed to photosystem II more effectively than red light (∼679nm) at light intensities below the photosaturation limit. Conversion of absorbed photons into photosynthetic oxygen evolution was maximised at 625nm; however, this maximum is unstable since neighbouring wavelengths (646nm) resulted in the lowest photosystem II operating efficiency. Identifying the wavelength-dependence of photosynthesis has clear implications to optimising growth efficiency and hence important economic implications to the algal biofuels and bioproducts industries.

Photosynthetic acclimation of Nannochloropsis oculata investigated by multi-wavelength chlorophyll fluorescence analysis

Multi-wavelength chlorophyll fluorescence analysis was utilised to examine the photosynthetic efficiency of the biofuel-producing alga Nannochloropsis oculata, grown under two light regimes; low (LL) and high (HL) irradiance levels. Wavelength dependency was evident in the functional absorption cross-section of Photosystem II (σII(λ)), absolute electron transfer rates (ETR(II)), and non-photochemical quenching (NPQ) of chlorophyll fluorescence in both HL and LL cells. While σII(λ) was not significantly different between the two growth conditions, HL cells upregulated ETR(II) 1.6–1.8-fold compared to LL cells, most significantly in the wavelength range of 440–540nm. This indicates preferential utilisation of blue-green light, a highly relevant spectral region for visible light in algal pond conditions. Under these conditions, the HL cells accumulated saturated fatty acids, whereas polyunsaturated fatty acids were more abundant in LL cells. This knowledge is of importance for the use of N. oculata for fatty acid production in the biofuel industry.

Future algal biofuels: implications of environmental temperature on production strain selection

Current and future economic mass production of microalgae or cyanobacteria will require suitable, preferably relatively high, levels of photosynthetically active radiation (PAR). Most large-scale productions sites, as well as those under development or under consideration, have been located between 40N and 40S raising the possible issue of the algae being periodically, or routinely, subjected to elevated temperatures (>30°C). The effects of environmental temperatures in the range 8–35°C on the marine, oleaginous model alga Nannochloropsis oculata were assessed. Active growth was observed at all temperatures except 35°C, where cells bleached and died. The implications of elevated temperature regimes were assessed for a variety of potential biofuel producing, biotechnologically relevant freshwater, marine and hyper-saline algae and the implications for their biotechnological exploitability discussed.

Microbial utilization of aqueous co-products from hydrothermal liquefaction of microalgae Nannochloropsis oculata

Hydrothermal liquefaction of algae biomass is a promising technology for the production of sustainable biofuels, but the non-oil, aqueous co-product of the process has only been examined to a limited extent. The aqueous phase from liquefaction of the alga Nannochloropsis oculata (AqAl) was used to make growth media for model heterotrophic microorganisms Escherichia coli, Pseudomonas putida, and Saccharomyces cerevisiae. Growth rates, yields, and carbon/nitrogen/phosphorus uptake were measured. E. coli and P. putida could grow using AqAl as the sole C, N, and P source in media containing 10vol.%–40vol.% AqAl with the best growth occurring at 20vol.%. S. cerevisiae could grow under these conditions only if the media were supplemented with glucose. The results indicate that in a biorefinery utilizing algae liquefaction, the aqueous co-product may be recycled via microbial cultures with significantly less dilution than previously published methods.

Flocculation Optimization of Microalga Nannochloropsis oculata

The objective of this work was to understand and optimize the flocculation of a marine alga Nannochloropsis oculata with two cationic salts, aluminum sulfate (AS), and ferric chloride (FC). Based on single-factor and response-surface-methodology experiments, second-order polynomial models were developed to examine the effect of initial algal biomass concentration (IABC), pH, and flocculant dose (FD) on final solid concentration of algae (SCA). The experimental and modeling results showed that SCA favored low pH, which however was undesirable to biomass recovery rate. There existed a positive stoichiometric relationship between FD and IABC; higher IABC required higher FD, and vice versa, for higher SCA. Optimum flocculation conditions were predicted at IABC of 1.7 g/l, pH8.3, and FD of 383.5 μM for AS, and IABC of 2.2 g/l, pH7.9, and FD of 438.1 μM for FC, under which the predicted maximum SCA were 32.98 and 30.10 g/l using AS and FC, respectively. The predictions were close to validation experimental results, indicating that the models can be used to guide and optimize the flocculation of N. oculata using AS and FC as the flocculants.

Early detection of protozoan grazers in algal biofuel cultures

Future micro-algal biofuels will most likely be derived from open-pond production systems. These are by definition open to “invasion” by grazers, which could devastate micro-algal mass-cultures. There is an urgent requirement for methodologies capable of early detection and control of grazers in dense algal cultures. In this study a model system employing the marine alga Nannochloropsis oculata was challenged by grazers including ciliates, amoebae and a heterotrophic dinoflagellate. A FlowCAM flow-cytometer was used to detect all grazers investigated (size range <20–>80μm in length) in the presence of algae. Detection limits were <10cellsml−1 for both “large” and “small” model grazers, Euplotes vannus (80×45μm) and an unidentified holotrichous ciliate (∼18×8μm) respectively. Furthermore, the system can distinguish the presence of ciliates in N. oculata cultures with biotechnologically relevant cell densities; i.e. >1.4×108cellsml−1 (>0.5gl−1 dry wt.).

Unusual Nuclear Division in Nannochloropsis oculata (Eustigmatophyceae, Heterokonta) which May Ensure Faithful Transmission of Secondary Plastids

Nuclear and plastid division in the monoplastidic, unicellular eustigmatophyte alga Nannochloropsis oculata (Heterokonta) was investigated by electron microscopy. The outermost of four membranes of the secondary plastid is continuous with the outer nuclear envelope membrane to form a nucleus-plastid continuum (NPC). Such physical continuity between the nucleus and the plastid is maintained throughout the cell cycle. Mitosis takes place in a closed spindle. In prophase, a barrel-shaped nuclear pole body (BR-NPB), emanating microtubules towards the cytoplasm, was detected in the vicinity of the nuclear poles. In metaphase, instead of the BR-NPB, a boomerang-shaped nuclear pole body (BM-NPB) occupied the spindle poles, projecting microtubules towards the opposite pole. The BR- and BM-NPB may function as a microtubule organizing centre (MTOC) but are distinct in morphology from any known MTOCs. During anaphase/telophase, the nucleus undergoes constriction with the microtubules penetrating the nucleus along the pole-to-pole spindle axis. The final stage of the nuclear division takes place in an unusual fashion such that the compartment of the inner nuclear envelope divides in advance of that of the outer nuclear envelope. Such unusual nuclear division is discussed in relevance to transmission of the secondary plastid. The present study provides the first report for nuclear and plastid division in Eustigmatophyceae.

Proteomic Analysis of Cadmium-Induced Protein Profile Alterations from Marine Alga Nannochloropsis oculata

Protein profile alterations following exposure to cadmium were examined in marine alga Nannochloropsis oculata through proteomic analysis. Alterations of the protein expression patterns following 10 muM cadmium treatment were analyzed on 2-dimensional gels. Out of 380 protein spots detected on 2-D gel using Coomassie staining, 11 spots were changed significantly following cadmium treatment. Because of the non-availability of molecular background information on this non-sequenced algal species, cross-species protein identification through ESI-Q-TOF MS/MS was used to identify altered proteins. Two newly induced proteins were identified as malate dehydrogenase orthologue and NADH dehydrogenase orthologue. One suppressed protein was identified to be glyceraldehydes 3-phosphate dehydrogenase A. Protein spot showing a 3-fold increase was identified as mitochondrial NADH: ubiquinone oxidoreductase orthologue. However, we could not find any matches in the database from ESI-Q-TOF MS/MS for the remaining seven proteins, thus only partial peptide sequences of these proteins were found.

Competition between the rotifer Brachionus rotundiformis and the ciliate Euplotes vannus fed on two different algae

The ciliate Euplotes vannus is a common protozoan in mass cultures of rotifers, and rapid reproduction of E. vannus occasionally reduces the rotifer yield. We performed a competition experiment between the rotifer Brachionus rotundiformis and the ciliate E. vannus. The ciliate was inoculated at three stages of the rotifer growth curve: the lag phase, the logarithmic growth phase and the stationary phase. When feeding on the alga Tetraselmis tetrathele, the ciliate increased and the rotifer growth was suppressed. The interference with rotifer growth was stronger in the lag and stationary phases than in the logarithmic growth phase. In contrast, when feeding on the alga Nannochloropsis oculata, the ciliate did not increase and the rotifer growth was similar to the control. In addition to the competition experiments, 15N incorporation experiments were performed on the ciliate to investigate its food preference. The nitrogen incorporation rates (% of body nitrogen h −1) of the ciliate were 0.7% through dead algae and 1.9% through rotifer feces when using T. tetrathele, and 0.4% through dead algae and 3.4% through rotifer feces when using N. oculata. The incorporation rate through bacteria-free rotifer feces was about one-third that of normal rotifer feces. These results indicated that the ciliate did not incorporate algal nitrogen directly, but rather through the microbial food chain, from phytoplankton to rotifer feces to bacteria. E. vannus incorporated the nitrogen of N. oculata and grew for a short time but the growth was soon suppressed. This growth inhibition may be due to allelopathy of N. oculata for E. vannus. Consequently, we propose that periodic addition of N. oculata should control E. vannus, and that this technique of applying allelopathy should be more sustainable than conventional treatments.

Life history and propagation of the endangered dromedary pearlymussel (Dromus dromas) (Bivalvia:Unionidae)

The reproduction, demography, and propagation of the endangered dromedary pearly- mussel (Dromus dromas) (Lea, 1834) were studied in the Clinch and Powell rivers, Tennessee. Viable populations of the dromedary pearlymussel now occur only in the Clinch and Powell rivers; the species has been extirpated from the remaining portions of its range in the Cumberland and Ten- nessee river drainages. Females are long-term winter brooders, and they are gravid from October to June. Glochidia are contained in conglutinates that are red to white and resemble freshwater leeches or flatworms. Conglutinates are 20 to 40 mm long and are released through the excurrent aperture. Estimates of fecundity based on 7 gravid females collected from the Clinch River were 55,110 to 253,050 glochidia/mussel. The ages of 66 valves of D. dromas were determined by thin-sectioning and ranged from 3 to 25 y. Annual growth averaged 5 mm/y until age 10 and decreased to ;1.2 mm/ y thereafter. Nineteen fish species were tested for suitability as hosts for glochidia. Ten were confirmed as hosts through induced infestations of glochidia: black sculpin (Cottus baileyi), greenside darter (Etheostoma blennioides), fantail darter (Etheostoma flabellare), snubnose darter (Etheostoma simoterum), tangerine darter (Percina aurantiaca), blotchside logperch (Percina burtoni), logperch (Percina caprodes), channel darter (Percina copelandi), gilt darter (Percina evides), and Roanoke darter (Percina roanoka). Juveniles produced from these hosts were cultured in dishes held in nonrecirculating aquaculture systems containing fine sediment (,105 mm) and were fed the green alga Nannochloropsis oculata every 2 d. Survival of 2810 newly metamorphosed juveniles was 836 (29.7%) after 1 to 2 wk.

Mitochondrion-dividing Ring in an Alga Nannochloropsis oculata (Eustigmatophyceae, Heterokonta)

The mitochondrion-dividing ring (MD ring) is an electron-dense annular structure at the isthmus of constricting mitochondria, which was first found in a primitive red alga Cyanidioschyzon merolae (Kuroiwa et al. 1993, 1995). However, there has been no evidence for its existence in other organisms. In the present study, mitochondrial division of a unicellular eustigmatophyte alga Nannochloropsis oculata was examined by transmission electron microscopy. Three-dimensional reconstruction of serial thin sections revealed the MD ring girdling the isthmus of the constricting mitochondria. This suggests that the MD ring is conserved in eustigmatophytes distant from rhodophytes in phylogeny.

Cadmium-induced changes in antioxidant enzymes from the marine alga Nannochloropsis oculata

Cadmium-induced oxidative stress symptoms such as lipid peroxidation and H2O2 production were examined in the marine alga Nannochloropsis oculata. Changes in antioxidant enzyme levels and isozyme patterns were also examined. Increasing concentrations of Cd produced growth inhibition. Among the responses to added Cd, the H2O2 content and malonyldialdehyde accumulation increased significantly, indicating a state of oxidative stress. In the case of ascorbate peroxidase activity the increase was about 2.5 times and a marked induction of the isozyme APX2 contributed to this increase. Guaiacol peroxidase activity increased about 4-fold, this being due mainly to the isozyme GPX3. Catalase activity increased slightly, whereas superoxide dismutase and glutathione reductase activity decreased markedly. Alterations of antioxidant enzyme levels and isozyme pattern changes in Cd-treated alga suggest that they might be involved in the heavy metal tolerance in this alga.

Effect of dissolved inorganic carbon concentration on oxygen production of a unicellular alga Nannochloropsis oculata

Effect of dissolved inorganic carbon concentration on oxygen production of a unicellular alga Nannochloropsis oculata