Nannochloris Oculata Research Articles

Effect of light spectra on microalgal biofilm: Cell growth, photosynthetic property, and main organic composition

The light spectrum is an important parameter that affects microalgae growth, but to date has not been thoroughly studied in microalgae biofilm-based systems. In this study, the effect of light spectra on biofilms of two microalgae (Chlorella sp. and Nannochloris oculata) was explored by investigating their growth, photosynthetic property, and main organic composition cultured under white, blue, green, and red light. The results indicated that blue light and red light were more efficient in enhancing cells’ growth than white light. Microalgae cultured under blue light had higher photosynthetic and photoprotective capability. The highest lipid accumulation was achieved for microalgae cultured under blue light, while the highest carbohydrate accumulation was obtained under red light. Protein accumulation in cells cultured under these four light conditions were almost the same. The results of this study may have important implications in selecting suitable light spectra for microalgae biofilm-based cultivation systems.

Cell Surface Energy Affects the Structure of Microalgal Biofilm.

Microalgae biofilm-based culture systems have wide applications in environmental engineering and biotechnology. Biofilm structure is critical for the transport of nutrients, gas, and signaling molecules in a microalgal biofilm. This work aims to understand the influence of cell surface energy (SE) on the microalgal biofilm structure. Three microalgae species were used as model cells in the study: Chlorella sp., Nannochloris oculata, and Chlorella pyrenoidosa. First, by mediating biofilm culture conditions, we obtained Chlorella sp. cells with SEs of 40.4 ± 1.5, 44.7 ± 1.0, and 62. 7 ± 1.2 mJ/m2, N. oculata cells with SEs of 47.7 ± 0.5, 41.1 ± 1.0, and 62.6 ± 1.2 mJ/m2, and C. pyrenoidosa cells with SEs of 64.0 ± 0.6, 62.1 ± 0.7, and 62.8 ± 0.6 mJ/m2. Then, based on the characterizations of biofilm structures, we found that cell SE can significantly affect the microalgae biofilm structure. When the cell SEs ranged from 40 to 50 mJ/m2, the microalgae cells formed heterogeneous biofilms with a large number of open voids, and the biofilm porosity was higher than 20%. Alternatively, when the cell SEs ranged from 50 to 65 mJ/m2, the cells formed a flat, homogeneous biofilm with the porosity lower than 20%. Finally, the influencing mechanism of cell SE on biofilm structure was interpreted based on the thermodynamic theory via analyzing the co-adhesion energy between cells. The study has important implications in understanding factors that influence the biofilm structures.

Influence of Photoperiods on Microalgae Biofilm: Photosynthetic Performance, Biomass Yield, and Cellular Composition

Microalgae have immense potential as biological sources to produce biofuels and high-value biomolecules. Biofilm-based microalgae cultivation has attracted much interest recently because of its high biomass productivity, reduced water use, and low cost of harvesting. This study aimed to understand the effect of photoperiod on three microalgae biofilms, including Nannochloris oculata, Chlorella sp., and Chlorella pyrenoidosa. The examined photoperiods were 3:3 s, 5:5 s, 30:30 min, 12:12 h (light-period-to-dark-period ratio), and continuous lighting. By determining the maximum quantum yield and relative electron transport rate of photosystem II, we found that photoperiods on the seconds scale improved photosynthetic performance of microalgae biofilm. Biomass yield and lipid content of these three microalgae cultured under the photoperiod with the seconds scale increased by 11%–24% and 7%–22%, respectively, compared with those cultured under continuous lighting. In addition, the photoperiods of 3:3 s, 5:5 s, 30:30 min, and 12:12 h were beneficial for protein synthesis. These results have important implications in establishing suitable light regimes for microalgae biofilm-based cultivation systems.

Impaired reproduction and individual growth of the water flea Daphnia magna as consequence of exposure to the non-ester pyrethroid etofenprox.

The effect of the pesticide etofenprox (0.76, 0.95, 1.18, 1.48, and 1.85μgL-1) on survival, reproduction, and growth of Daphnia magna organisms was monitored using 21-day exposure tests. In order to test pesticide effects on D. magna, survival, length, mean total neonates per female, mean brood size, time to first reproduction, mean number broods per female, cumulative molting, and the population parameter intrinsic rate of natural increase (r) were used. Reproduction was seriously affected by etofenprox. Concentrations of etofenprox higher than 1.18μgL-1affected all the reproductive parameters analyzed as well as individual length. However, daphnids' survival after 21days of pesticide exposure did not exhibited differences among experimental and control groups. The no observed effect concentration (NOEC), the lowest observed effect concentration (LOEC), and the maximum acceptable toxicant concentration (MATC) were calculated for the different parameters. A MATC estimation of 1.32μgL-1 was calculated for mean brood size, mean number of broods per female, mean number of neonates per female, and the intrinsic rate of growth population. Etofenprox effect on the algae Nannochloris oculata was also evaluated. The selected etofenprox concentrations did not affect algal growth rate (μ) after 24h; however, N. oculata exposed during 48 and 72h to the highest etofenprox concentration showed a decreased in its population rate.

Identification of microalgae by hyperspectral microscopic imaging system

ABSTRACTHarmful algal blooms can lead to serious environment problems, and thus monitoring and classifying microalgae have received increasing attention. Microcystis aeruginosa, Chlorella pyrenoidosa, and Nannochloris oculata all are small in size and have a similar morphology, which lead to discriminant difficulties using a traditional optical microscope. In this experiment, an independently developed hyperspectral microscopic imaging system was used to obtain the hyperspectral images of microalgae samples, and a hyperspectral dataset was developed through pretreated steps. Then the Fisher algorithm was employed to identify the species of the microalgae, and its sensitivity and specificity were found to be high. The result demonstrated that this method can classify the microalgae in a quick and convenient manner; in addition, the quantity and spatial information of the samples can be acquired.

Molecular identification and nanoremediation of microbial contaminants in algal systems using untreated wastewater

ABSTRACTWastewater-algal biomass is a promising option to biofuel production. However, microbial contaminants constitute a substantial barrier to algal biofuel yield. A series of algal strains, Nannochloris oculata and Chlorella vulgaris samples (n = 30), were purchased from the University of Texas, and were used for both stock flask cultures and flat-panel vertical bioreactors. A number of media were used for isolation and differentiation of potential contaminants according to laboratory standards (CLSI). Conventional PCR amplification was performed followed by 16S rDNA sequencing to identify isolates at the species level. Nanotherapeutics involving a nanomicellar combination of natural chitosan and zinc oxide (CZNPs) were tested against the microbial lytic groups through Minimum Inhibitory Concentration (MIC) tests and Transmission Electronic Microscopy (TEM). Results indicated the presence of Pseudomonas spp., Bacillus pumilus/ safensis, Cellulosimicrobium cellulans, Micrococcus luteus and Staphylococcus epidermidis strains at a substantial level in the wastewater-fed algal reactors. TEM confirmed the effectiveness of CZNPs on the lytic group while the average MICs (mg/mL) detected for the strains, Pseudomonas spp, Micrococcus luteus, and Bacillus pumilus were 0.417, 3.33, and 1.458, respectively. Conclusively, CZNP antimicrobials proved to be effective as inhibitory agents against currently identified lytic microbial group, did not impact algae cells, and shows promise for in situ interventions.

Cultivation study of the marine microalga Picochlorum oculatum and outdoor deployment in a novel bioreactor for high-density production of algal cell mass

Microalgae are considered a promising source of renewable diesel and jet fuel. Currently, large-scale microalgae cultivations are performed in open ponds because of their low capital and operating costs, but they generally suffer from low cell mass yield and high risk of contamination. A novel, cost-effective, and modular horizontal bioreactor (HBR) for algae cultivation was developed, as described in the present study. The HBR was designed to keep costs low and was engineered to minimize water and energy use while enhancing CO2 and nutrient uptake. The selected marine microalgal strain, Picochlorum oculatum (Nannochloris oculata), has shown potential for biofuel production. A series of controlled indoor growth experiments was first performed to identify the appropriate P. oculatum growth conditions before demonstrating the HBR performance. Supplying CO2 continuously or by pH-control (pulsed) did not affect culture progression. Growth on urea and nitrate yielded comparable results, while ammonium was less effective. Varying inoculum size from 10% to 15% or 20% had no significant effect on lag time and final cell concentration and comparable growth was measured in the 7–8 pH range. The 150-L HBR's performance was successfully demonstrated outdoors by growing P. oculatum at the identified growth conditions selected to reduce operating costs (pH-controlled CO2, pH 7.5, 10% inoculum, and nitrate). High-density growth was achieved without any contamination issues in outdoor HBR cultivations over 68 days in central Florida during two consecutive growth cycles.

Microcystis extracts and single cells have differential impacts on the demography of cladocerans: a case study on Moina cf. micrura isolated from the Mediterranean coastal shallow lake (L’Albufera, Spain)

Cyanobacteria often have a deleterious effect on zooplankton. We hypothesized that the presence of either M. aeruginosa cells or microcystin extracts from M. aeruginosa would have a significant impact on the population growth rate, survivorship, and fecundity of Moina cf. micrura isolated from L’Albufera, Valencia, Spain. The cladocerans were exposed to different concentrations of Microcystis extracts on a diet of Nannochloris oculata (Chlorococcales) as well as different proportions of Microcystis single cells and N. oculata. Cyanotoxins were extracted from a Microcystis bloom by its repeated freezing, thawing, and sonication. Total microcystin concentration was 138.2 µg l−1. M. aeruginosa single cells were obtained by sonication. We used five microcystin concentrations (from 4.3 to 69.1 µg l−1 and controls without microcystins) with non-toxic Nannochloris oculata at 0.5 × 106 cells ml−1 as diet or on different proportions of M. aeruginosa single cells and N. oculata. Microcystin reduced generation time and longevity of M. cf. micrura but increased daily production of offspring. Single-celled Microcystis (100%) diet for Moina cf. micrura decreased growth rates compared with treatments using cyanotoxin extracts. We suggest routine testing of cyanobacterial crude extracts using plankton to estimate harmful impacts of blooms especially for drinking water reservoirs.

English

The use of microalgae in wastewater treatment and its biotechnological exploitation for the production of biofuels is a potential environmental application. Some species of microalgae are notable due to their lipid composition and fatty acid profile suitable for biofuel production. During the present study, a factorial 23 experimental design was conducted, which assessed three factors: i) two species of microalgae (Chlorella vulgaris and Nannochloris oculata), ii) two types of culture media [wastewater of tilapia farming (WTF) and bold’s basal medium (BB)], and iii) two types of lighting (multi-LED lamps and white light). Microalgae were inoculated in photobioreactors in 6 L of medium (WTF or BBM) at an initial concentration of 1.0 × 106 cells ml-1 at 20 ± 2°C. The highest average cell density as well as the highest productivity of biomass observed in the treatments was C. vulgaris treatment in BBM and multi-LED lighting (8.83 × 107 cells ml-1 and 0.0854 g l-1 d-1, respectively). Although the majority of lipid productivity was obtained in the exponential phase of N. oculata cultivated in multi-LEDs in both treatments (BBM with 58% and WTF with 52%), cultivation of both species was generally maintained in WTF and were those that presented the major lipid productivity (2-18 mg l-1 d-1) in comparison with those cultivated in BBM. Palmitic, stearic, oleic, linoleic, linolenic and eicosanoic (C16–C20) fatty acids were present in both species of microalgae in concentrations between 26 and 74%. Based on the results of the present study, we conclude that cultivation of N. oculata and/or C. vulgaris in WTF illuminated with multi-LEDs is an economic and sustainable alternative for biodiesel production because it can represent up to 58% of lipids with a fatty acid profile optimal up to 74% of the total fatty acids.   Key words: Chlorella vulgaris, Nannochloris oculata, production of fatty acids, wastewater of tilapia farming, production of biofuels.

The values of whole algae and lipid extracted algae meal for aquaculture

This research applies hedonic pricing methods to value whole algae and lipid-extracted algae (LEA) for aquaculture. Prices and nutritional characteristics for commonly applied aquaculture feed ingredients are used to determine the values of whole algae and LEA based on their nutrient compositions. The results show that whole Chlorella pyrenoidosa will have a higher value than soybean meal and a lower value than menhaden fishmeal. Results show that whole Nannochloris oculata and N. oculata LEA will have a lower value than both soybean meal and menhaden fishmeal.

Rapid spectrophotometric method for determining surface free energy of microalgal cells.

Microalgae are one of the most promising renewable energy sources with environmental sustainability. The surface free energy of microalgal cells determines their biofouling and bioflocculation behavior and hence plays an important role in microalgae cultivation and harvesting. To date, the surface energetic properties of microalgal cells are still rarely studied. We developed a novel spectrophotometric method for directly determining the surface free energy of microalgal cells. The principles of this method are based on analyzing colloidal stability of microalgae suspensions. We have shown that this method can effectively differentiate the surface free energy of four microalgal strains, i.e., marine Chlorella sp., marine Nannochloris oculata, freshwater autotrophic Chlorella sp., and freshwater heterotrophic Chlorella sp. With advantages of high-throughput and simplicity, this new spectrophotometric method has the potential to evolve into a standard method for measuring the surface free energy of cells and abiotic particles.

Effects of indirect toxicity of interacting Cd–Zn in a planktonic marine system

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 19:19-28 (2013) - DOI: https://doi.org/10.3354/ab00507 Effects of indirect toxicity of interacting Cd–Zn in a planktonic marine system Orlando Jara1,*, Adriana Aránguiz-Acuña2 1Biología Marina, Facultad de Ecología y Recursos Naturales, Universidad Andres Bello, República 440, Santiago, Chile 2Departamento de Química, Facultad de Ciencias, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile *Email: orlandoandres.jara@gmail.com ABSTRACT: Traditional toxicity bioassays usually assess the effects of single substances on isolated species, which does not, however, allow the identification of potential effects in natural systems. In addition, quantitative estimations of metal uptake in top consumers due to feeding are generally focused on the individual level and do not evaluate the consequences of metal addition at demographic or population levels. An experimental system, composed of the marine microalga Nannochloris oculata Droop, 1955 and the herbivorous rotifer Brachionus plicatilis Müller, 1786, was implemented in order to evaluate (1) whether the interaction of 2 metals, Cd and Zn, causes a greater toxic effect on planktonic species than that obtained through the addition of single metals and (2) whether the toxicity of these metals on a target herbivore population increases through the indirect route of food intake. Factorial experiments were developed, and results indicated that the toxicity on populations was higher when metals were combined, suggesting resource-dependent interaction. Consumption of contaminated algae had a negative effect on the growth rate of B. plicatilis, driven mainly by decreased juvenile and adult survival. This effect was opposite to the direct effect of dissolved metals in the medium. It is suggested that assessment of the interaction between toxic substances, as well as between populations, inserted in trophic networks, is necessary when quantifying the effects of disturbances on marine populations. Finally, our results highlight the relevance of indirect effects using a purely demographic tool focused on population level. KEY WORDS: Metals · Bioassays · Population assessment · Rotifers · Food webs · LTRE · Life table response experiment Full text in pdf format PreviousNextCite this article as: Jara O, Aránguiz-Acuña A (2013) Effects of indirect toxicity of interacting Cd–Zn in a planktonic marine system. Aquat Biol 19:19-28. https://doi.org/10.3354/ab00507 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 19, No. 1. Online publication date: July 25, 2013 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2013 Inter-Research.

Harvesting Nannochloris oculata by inorganic electrolyte flocculation: Effect of initial cell density, ionic strength, coagulant dosage, and media pH

Process variables affecting harvesting efficiency of Nannochloris oculata by AlCl3 flocculation such as, cell density, ionic strength, coagulant dosage, media pH, and cell surface charge were investigated. Initial cell density and coagulant dosage had a significant effect on the removal efficiency; however, levels of ionic strength tested were not significant. Best flocculation conditions of investigated variables were: 0.0016ng of AlCl3/cell, 3.0×107cell/mL, and pH 5.3. Removal efficiency at optimum conditions and salt concentrations of: 0, 15, and 30g/L NaCl was 96, 98, and 97 %, respectively. Low cell density cultures ∼106cell/mL, required five times greater AlCl3 dosage to achieve the same removal efficiency. Destabilization of algal cultures using 0.0032ng of AlCl3/cell was observed by reducing the zeta potential to −22mV. Acidification with HCl for conducting flocculation at pH 5.3 could be a significant cost burden unless is mitigated by selecting a low-buffering-capacity media.

Effect of High Pressure Homogenization on Aqueous Phase Solvent Extraction of Lipids from Nannochloris Oculata Microalgae

The ability to extract lipids from high-moisture Nannochloris Oculata algal biomass disrupted with high pressure homogenization was investigated. During the first phase, the effect of high pressure homogenization (system pressure and number of passes) on disrupting aqueous algae (of different concentrations and degree of stress) was investigated. Se-condly, the effect of degree of cell wall disruption on the amount of lipids extracted with three solvents, namely: hexane, dichloromethane and chloroform, were compared. Studies reveled that high pressure homogenization is effective on cell disruption while the amount of system pressure being the most significant factor affecting the degree of cell breakage. Al-though the number of passes had some impact, the level of disruption seemed to level-off after a certain number of passes. The study revealed that slightly polar solvents (such as chloroform and dichloromethane) performed better in aqueous-phase lipid extractions as compared to hexane. Also, it was revealed that it was not necessary to disrupt the algal cells completely to achieve appreciable levels of lipid yields. In fact, conditions that exerted only 20% of the cells to completely disrupt, allowed sufficient damage to liberate most of the lipids contained in the remainder of the cells.

굴, Crassostrea gigas 유생 성장단계별 미세조류 12의 소화도

Twelve species of food microalgae were investigated to clarify the digestion index of Crassostrea gigas larvae using epifluorescence microscopy to choose an appropriate diet for artificial seed production in hatchery. An experiment was conducted using 1 (D shaped stage), 4 (Early umbo stage), 8 (umbo stage) and 12 (Full grown stage) days old larvae. larvae were stocked in 1 L flasks at 5 individuals/mL and fed 10×10 4 algal cells/mL of each species individually. Prior to larvae were fed for 3 h and then were observed under the microscope to detect ingestion; larvae were then sieved and replaced in 1 L flasks containing filtered seawater and were observed after 3, 5 and 8 h to analyse the digestion index. Values of digestion indices were specific for each alga. No evidence for the ingestion of Thalassiosira weissflogii was evident at all larval development stages tested. Digestion indices of others microalgae were 0.8-99.7% at 4 stage of larval development stages: Chlorella ellipsoidea (0.8-5.4%), Nannochloris oculata (1.4-5.0%), Isochrysis galbana (99.1-99.5%), Pavlova lutheri (99.1-99.5%), I. aff. galbana (99.4-99.5%), Cheatoceros calcitrans (0.0-99.2%), C. gracilis (0.0-99.7%), C. simplex (0.0-95.9%), Phaeodactylum tricornutum (0.0-99.6%), Tetraselmis tetrathele (0.0-99.7%) and Dunaliella tertiolecta (0.0-99.6%), respectively. Therefore, it is assumed that food microalgae showing the high digestion such as I. galbana should be supplied to the early umbo stage larvae, and then after the umbo larval stage, the mixed microalgae with diatoms and light green algae should be supplied to the full grown stage larvae to increase the digestion of their larvae.

굴, Crassostrea gigas 유생의 먹이생물 섭취 크기

ABSTRACT Digestibility index of 12 phytoplankton species were invested during the larval development sizes. Ingestible size of phytoplankton varied depending on larval sizes: Isochrysis galbana , I. aff . galbana , Pavlova lutheri , Chlorella ellipsoidea , Nannochloris oculata was ingested 94.2-99.7% all larval sizes. Cheatoceros calcitrans , C. gracilis and C. simplex could ingest over 90.0% after umbo stage (mean shell length 189.3 ± 13.8 μm). Phaeodactylum triconutum , Dunaliella tertiolecta and Tetraselmis tetrathele could not ingested D-shaped larvae (shell length 65.0-100.0 μm) but ingested 97.3-99.7%, 43.3-99.3%, 48.5-99.3% after then larval stages, respectively. But Thalassiosira weissflogii was ingested 1.0-1.7% only at full grown stage. Over 50.0% ingestion cell size was D-shape stage larvae with smaller than mean 102.3 μm in shell length could ingest phytoplankton with 4.6 μm in both major and minor axis and up to 9.3 μm in minor axis basis for larger than mean 158.3 μm in shell length, respectively. At all larval stages, phytoplankton with larger than 10.0 μm in both major and minor axis could not be ingested.

보관 방법에 따른 Rotifer Brachionus plicatilis 내구란의 부화

The rotifer Brachionus plicatilis is one of the most important food organisms in aquaculture. The resting eggs pro-duced by mictic female rotifers are easily stored and hatched, making them useful as the starter for the mass culture of rotifers in marine larval culture. This study examined the optimum preservation method for resting eggs to ensure a high hatching rate. To produce resting eggs, the marine rotifer B. plicatilis was cultured with Nannochloris oculata (KMMCC 16). The resting eggs were harvested and cryopreserved using 5% and 10% methanol (MeOH), dimeth-ylsulfoxide (DMSO), and glycerol as cryoprotectant agents (CPAs). The cryopreservation comprised slow or rapid freezing and the resting eggs were stored for one month in liquid nitrogen (-196˚C). The resting eggs were also dried at different temperatures (30, 40, and 50˚C) and for different times (1, 2, and 3 h). In general, the hatching rates of the resting eggs preserved with CPA were higher than those without CPA and the slow freezing method was better than the rapid freezing method. However, the optimum CPA concentration for the hatching rate of the resting eggs varied with the freezing method and kind of CPA, and the CPA also affected the viability of the resting eggs. Dried resting eggs had a high, rapid hatching rate over 80%. The moisture content of the resting eggs cryopreserved in liquid nitro-gen affected the hatching rate. Drying at 30˚C for 1 hour resulted in a high hatching rate of the resting eggs. In con-clusion, drying at 30˚C for 1 hour and preservation in liquid nitrogen with the slow freezing method, without CPA, is recommended for a high hatching rate (ca. 95%) of rotifer resting eggs.Key words:Brachionus plicatilis, Cryopreservation, Dry, Hatching rate, Resting eggs

온도와 염분이 Rotifer Brachionus plicatilis와 B. rotundiformis의 성장과 크기에 미치는 영향

Rotifers of the genus Brachionus are commonly used as a live food for larval fish, and rotifers of different sizes are preferred according the mouth size of the fish. Rotifer species vary in size, and individual size can depend on the temperature and salinity of the rearing environment. We investigated the effects of temperature and salinity for two species, B. plicatilis (250-300 ) and B. rotundiformis (100-220 ). Two strains of B. plicatilis (CCUMP 36 and 48) and two strains of B. rotundiformis (CCUMP 51 and 56) were received from the Culture Collection of Useful Marine Plankton (CCUMP) at Pukyong National University and cultured with the green alga, Nannochloris oculata (KMMCC 16) from the Korea Marine Microalgal Culture Center (KMMCC). The growth and size of rotifers were examined at three water temperatures (, , ) and four salinities (20 psu, 25 psu, 30 psu, 35 psu) under continuous light (40 ). The maximum density and growth rate of B. rotundiformis were greater than those of B. plicatilis. The lorica length of B. plicatilis ranged from 215.4 to 269.7 and from 154.9 to 206.6 for B. rotundiformis, depending on strain, temperature and salinity. Rotifers were smaller when cultured at high temperatures, regardless of salinity. B. rotundiformis preferred higher salinity than B. plicatilis. The results demonstrated that the size of rotifers could be controlled to some extent by temperature and salinity.

Serial optimization of biomass production using microalga Nannochloris oculata and corresponding lipid biosynthesis

As energy and environment have become urgent issues, there has been increasing needs to develop alternative energy source, such as microalgal bio-fuel. In this study, we investigated the growth and lipid contents of microalgae Nannochloris oculata under various environmental conditions for biodiesel production. Our results indicated that biomass productivities of N. oculata were correlated with increasing nitrogen concentrations up to 37.5 ppm. High irradiance using 230-250 μmol/m(2) led to higher biomass yields than low irradiance of 160-180 μmol/m(2). Biomass productivities increased further by manipulating surface to volume ratio (S/V), which in turn enhanced light penetration. Finally, optimal biomass productivities (1.04 g/l day) could be achieved by the supplementation of yeast extract. Lipid contents and fatty acid profiles of N. oculata were affected by the different growth conditions. Lipid contents of N. oculata decreased as nitrogen concentration increased. Lower temperature (15 °C) resulted in higher lipid content than higher temperature (25 °C). Fatty acid profiles of N. oculata indicated that palmitic acid (C16:0) and linoleic acid (C18:2) were the two most abundant fatty acids, but the supplementation of yeast extract increased linolenic acid (C18:3) content. Our results suggested the feasibility of N. oculata for the biodiesel production.

Biosorption of chromium (Cr(III)/Cr(VI)) on the residual microalga Nannochloris oculata after lipid extraction for biodiesel production

In order to increase the economic feasibility of biodiesel production from microalgae, the residual biomass after biodiesel production can be utilized as biosorbent for heavy metal removal. In this study, biosorption of chromium by residual Nannochloris oculata after lipid extraction was investigated. Increased surface area of N. oculata was observed after lipid extraction. Cr(III) removal increased as the pH increased from 2 to 6, while Cr(VI) removal was highest at pH 2 and it decreased with the increase in pH. Cr(VI) was reduced to Cr(III) in the presence of biomass under acidic conditions; X-ray photoelectron spectroscopy revealed that the converted Cr(III) was bound to the biomass. Chromium removal was significantly enhanced at high chromium concentrations, which indicates that surface reactions may occur at high chromium/biomass ratios. FTIR study indicated that phosphate and carboxyl functional groups of the biomass were mainly responsible for chromium binding.