Effects of nitrogen source and growth phase on proximate biochemical composition, lipid classes and fatty acid profile of the marine microalga Isochrysis galbana (original) (raw)
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Microbiology and Biotechnology Letters
The properties of microalgae as bioresources for biodiesel production can be improved by adding nitrogen sources into the culture medium. Thus, Nannochloropsis oceanica CCAP 849/10 was cultured in f/2 media supplemented with five different forms of nitrogen at 0.88 mmol-N l-1 each: ammonium bicarbonate (NH 4 HCO 3), ammonium sulfate ((NH 4) 2 SO 4), sodium nitrate (NaNO 3), ammonium nitrate (NH 4 NO 3), and urea. The cell density, lipid content, and fatty acid profile of the microalga were determined after 15 days of cultivation. The growth of N. oceanica based on cell number was lowest in the medium with NH 4 NO 3 , and increased significantly in the medium with NH 4 HCO 3. Cells treated with (NH 4) 2 SO 4 , and NH 4 NO 3 produced the highest total lipid contents (i.e., 65% and 62% by dry weight, respectively). The fatty acid profiles of the microalga were significantly different in the various nitrogen sources. The major fatty acids detected in cultures supplemented with NH 4 HCO 3 , (NH 4) 2 SO 4 , NH 4 NO 3 , or urea were C14:
Frontiers in Marine Science
Microalgae are regarded as a promising alternative that can replace fishmeal and fish oil in aquaculture. Under N-limitation, many microalgae species change their carbon storage patterns in favor of neutral lipids (NLs) mainly in the form of triacylglycerol (TAG), but fatty acids in polar lipids (PL) are nutritionally more available for fish than those esterified into NLs. In the present study, the effect of N-limitation on the lipid content and fatty acid profiles in different lipid classes of Phaeodactylum tricornutum, Isochrysis aff. galbana clone T-Iso, Rhodomonas baltica, and Nannochloropsis oceanica were investigated. The microalgae cells were cultivated by two different methods, batch and semi-continuous culture, to create strong and moderate N-limitation, and this in turn will significantly affect the biomass and lipid productivity. All four species accumulated lipids mainly in the form of TAG, in response to strong nitrogen limitation. N. oceanica, however, accumulated 51% of the dry weight as lipid in moderate nitrogen limitation and up to 87% of the fatty acid was in TAG. Isochrysis aff. galbana clone T-Iso was the only species where the fraction of polyunsaturated fatty acid (PUFA), especially the fraction of docosahexaenoic acid (DHA), increased with increasing nitrogen limitation. Total lipid productivity showed no increase in batch culture although stronger nitrogen limitation led to lipid accumulation. P. tricornutum had the highest eicosapentaenoic acid (EPA) content, while N. oceanica showed the highest EPA productivity due to the high content of lipid. The highest DHA productivity was found in Isochrysis aff. galbana clone T-Iso from moderate N-limitation, mainly due to the high biomass productivity. Based on the results from the current study, N. oceanica and T-Iso are two promising microalgae strains ass long-term sustainable sources of n-3 long chain-PUFAs under moderate N-limitation. As shown in the present study, increased lipid content in microalgal cells due to strong N-limitation induction may not increase the lipid productivity because biomass production is usually reduced. Therefore, a combination of approaches such as metabolic engineering, conditioning and selection may be needed to further increase the n-3 LC-PUFA productivity without substantial loss of biomass.
Journal of Applied Phycology, 1993
Three species of microalgae were grown in mass culture to investigate the influence of culture technique and growth phase on the production of 20:5(n-3) and 22:6(n-3). These polyunsaturated fatty acids (PUFA) are considered to be essential in many marine animals diets for high growth and survival rates. The species of microalgae examined were Nannochloropsis oculata, Pavlova lutheri and Isochrysis sp. (clone T.Iso). All batch cultures (logarithmic and stationary phase) and semi-continuous cultures (logarithmic phase) examined contained high levels of the long-chain (n-3) PUFA, but production could be maximised by harvesting at specific times and growth phases. Maximum cellular content (pg cell -) of long-chain PUFA was found in logarithmic phase batch cultures of N. oculata and in stationary phase cultures of P. lutheri. The cellular content of PUFA in cultures of Isochrysis sp. did not change significantly with culture technique or growth phase. Alternatively, stationary phase cultures of all three species showed increased proportions (%) and cellular contents of triacylglycerols, and saturated and monounsaturated fatty acids with correspondingly decreased proportions of polar lipids and most PUFA relative to logarithmic phase cultures. The exception was the proportion and cellular content of 22:6(n-3) in P. lutheri which increased with triacylglycerol content. The mass of long-chain (n-3) PUFA per volume of culture was significantly higher in stationary phase cultures due to the higher cell counts per volume. These findings indicate that the opportunity exists to maximise PUFA production by microalgae with the potential to improve animal growth and reduce production costs in mariculture operations and may be of use in the large scale culture and harvesting of microalgae for the biotechnology industry.
Journal of Applied Phycology
Marine microalgae are a promising sustainable source of lipids, omega-3 fatty acids, and carbohydrates. Selected microalgae species belonging to the Bacillariophyceae, Haptophyceae, Eustigmatophyceae, and Prasinophyceae were characterised for cellular content of carbon and nitrogen, and for production yields of lipids, fatty acids, total carbohydrates, and β-glucans. Carbon and nitrogen content showed a hyperbolic decrease with increasing cell numbers for Chaetoceros calcitrans, C. muelleri, Skeletonema costatum, Tetraselmis sp., and Nannochloropsis oculata. Cultures of Pavlova lutheri and Tisochrysis lutea showed an increase in carbon content per cell, but a decrease in nitrogen content. The total lipid content of C. muelleri, C. calcitrans, N. oculata, and T. lutea increased with decreasing relative growth rate; however, the highest productivity of lipids was found in T. lutea grown at 40% of the maximum specific growth rate. The highest content of eicosapentaenoic acid was found ...
Preservation of the marine microalga, Isochrysis galbana: influence on the fatty acid profile
Aquaculture, 1994
Preservation of marine microalgae is of interest for storage in culture collections as well as a method of having living biomass available for aquaculture feed. The present paper reports the effects of lyophilization, freezing and maintenance of refrigerated cell concentrates on the viability and fatty acid profile of Zsochrysis galbana. Lyophilization led to a viability loss of about 98%, and the initial fatty acid profile remained unchanged throughout the experiment (1 month). Survival rate after freezing was enhanced by a lOoh v/v glycerol addition and remained around 20% at the end of the experiment. No effect was observed on the fatty acid profile. A concentrate of 9 g.l-' maintained at 4°C for 30 days retained up to 85% viability. There was a significant decrease in saturated and mono-unsaturated fatty acids, while polyunsaturated content remained constant.
Lipid content and fatty acid profiles in ten species of microalgae
Idesia (Arica), 2015
The present study aimed to evaluate the lipid content and fatty acid profiles of 9 marine species (Nannochloropsis oculata, Thalassiosira pseudonana, Phaeodactylum tricornutum, Isochrysis galbana, Tetraselmis suecica, Tetraselmis chuii, Chaetoceros muelleri, Thalassiosira fluviatilis and Isochrysis sp.) and 1 freshwater microalga species (Chlorella vulgaris) that were cultivated in Erlenmeyer flasks with 800 mL of culture medium under stationary autotrophic conditions while exposed to a continuous photon flux density of approximately 175 μmol m -2 s -1 , a temperature of 25±2 o C and constant airflow. N. oculata and T. pseudonana exhibited the highest lipid content, although they had a high proportion of monounsaturated fatty acids relative to polyunsaturated fatty acids. C. vulgaris and Isochrysis sp. exhibited high levels of polyunsaturated fatty acids, whereas P. tricornutum, N. oculata and T. suecica exhibited the highest eicosapentaenoic acid levels, and I. galbana and C. muelleri had the highest docosahexaenoic fatty acid levels. The freshwater species C. vulgaris had the highest levels of linoleic and linolenic acids, followed by the marine species T. chuii.
Journal of Microbiology and Biotechnology, 2011
In order to investigate and generalize the effects of carbon and nitrogen sources on the growth of and lipid production in Chlorella sp. 227, several nutritional combinations consisting of different carbon and nitrogen sources and concentrations were given to the media for cultivation of Chlorella sp. 227, respectively. The growth rate and lipid content were affected largely by concentration rather than by sources. The maximum specific growth was negatively affected by low concentrations of carbon and nitrogen. There is a maximum allowable inorganic carbon concentration (less than 500~1,000 mM bicarbonate) in autotrophic culture, but the maximum lipid content per gram dry cell weight (g DCW) was little affected by the concentration of inorganic carbon within the concentration. The lipid content per g DCW was increased when the microalga was cultured with the addition of glucose and bicarbonate (mixotrophic) at a fixed nitrogen concentration and with the lowest nitrogen concentration (0.2 mM), relatively. Considering that lipid contents per g DCW increased in those conditions, it suggests that a high ratio of carbon to nitrogen in culture media promotes lipid accumulation in the cells. Interestingly, a significant increase of the oleic acid amount to total fatty acids was observed in those conditions. These results showed the possibility to induce lipid production of high quality and content per g DCW by modifying the cultivation conditions.
Effect of Two Different Nitrogen Sources on Lipid Accumulation in Microalgae Chlorella Pyrenoidosa
2017
In present scenario, microalgae have been used as a third generation promising source for production of biofuel. So it is necessary to screen microalgal strains rich in oil and adapt to variable environment conditions. The present study deals with cultivation of Chlorella pyrenoidosa in Fogg’s media using urea and KNO3 as nitrogen source. The effect of two different nitrogen sources at different concentration (0-2g/L) on biomass and lipid content was studied. The result showed that with increase of N-source in media biomass increased but lipid content decreases and vice versa. Moreover, at same concentration of urea and KNO3, biomass as well as lipid content was more in microalgal cell growing in urea. Urea at concentration of 0.1g/L gives optimum conditions for biomass production and lipid content in cells. At high concentration of urea due to ammonium toxicity growth rate decreased in algal culture. The optimum concentration of urea proves better than other nitrate source to cultu...
Algal Research, 2020
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.L 1), 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 nitrogendepleted 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.
Aquaculture, 1989
Fernandez-Reiriz, M.J., Perez-Camacho, A., Ferreiro, M.J., Blanco, J., Planas, M., Campos, M.J.