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)
The Egyptian Journal of Aquatic Research, 2019
Nitrogen represents a critical macronutrient that regulates the metabolism and consequently, the growth and biochemical composition of microalgae. In this study, the effect of different nitrogen concentrations (0, 36, 72, 144 and 288 mg/L) on the growth rate and biochemical composition of Isochrysis galbana was investigated. Cell growth, pigments and protein content of I. galbana biomass decreased with diminishing nitrogen concentration; while carbohydrates showed the highest value, 47%, in case of total nitrogen deprivation. Poly unsaturated fatty acids (PUFAs) increased five-fold under sufficient nitrogen concentrations (72 mg/L), compared to nitrogen deprivation. In contrast, concentration of saturated fatty acids (SFAs), 75.79% under nitrogen deprivation, was higher than in case of nitrogen sufficiency, 36.63%. The highest carbohydrate, protein and lipid productivities observed were 156.7, 326.2 and 264.6 mg/L under nitrogen concentrations of 72, 0 and 72 mg/L, respectively. The results of this study indicate that nitrogen concentration significantly affects the growth and biochemical compositions of I. galbana.
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:
Aquacultural Engineering, 1989
Cultures of the marine microalga Dunaliella tertiolecta were grown in nitrate, nitrite and urea at concentrations ranging from 0•25 to 16 mg atom. N/litre. Great biochemical variability has been shown in this microalga as a function of high nitrogen concentrations for all the sources used. Cellular protein and carbohydrates and gross energy per ml of culture increased proportionally to the increase in the N concentration, under conditions that maintain constant the N P ratio. Two kinds of cultures are defined: low nitrogen cultures <2 mg atom. N/litre, and high nitrogen cultures > 2 mg atom. N/litre. Variability mainly appears in the second type of cultures. Protein/cell values of up to 4•94, 5•47 and 1•41 times higher have been observed in nitrate, nitrite and urea cultures, respectively, when comparing protein/cell values obtained in high N cultures with those obtained in low N cultures. Similar variations have been observed in the carbohydrates/cell content, with values up to 3•16, 3•30 and 1•77 times higher in the high than in the low N cultures. Biochemical variability is greater in nitrate and nitrite cultures (inorganic sources of nitrogen) than in urea cultures (organic source of N). Lipid/carbohydrates ratio seems to be a convenient parameter for characterizing the physiological state of a microalgal population. This biochemical variability must have a marked effect on the value of this microalga as a source of single cell protein, chemicals or as feed in mariculture.
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.
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.
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.
Journal of Basic Microbiology, Wiley, 2019
The present investigation ascertains the impact of gradient concentrations of sodium nitrate on the physiology and biochemical composition of isolated microalga Scenedesmus rotundus-MG910488. The concentrations of nitrate were selected as 0, 3.5, 7.0, 10.5, 14.0, and 17.6 mM/L in BG 11 medium. The lower concentrations of nitrogen were found to be significantly decreasing the cell count and photosynthetic activity in the microalga as well as changing cell morphology. The amount of biomass, its productivity and lipid yield were significantly affected. The highest biomass of 689.15 ± 14.27 mg/L was achieved in the concentration of 17.6 mM/L with the biomass productivity of 38.28 ± 0.78 mg/L. The highest lipid accumulation of 41.46 ± 1.94% dry-cell weight was obtained at a concentration of 3.5 mM/L, whereas the lowest lipid accumulation of 29.22 ± 1.65% at the concentration of 17.6 mM/L sodium nitrate. The fatty acid composition determines the quality of the fuel, so the characterization of fatty acid methyl esters (FAMEs) was performed by GC, and the assessment of methyl esters of fatty acid confirmed the existence of palmitic acid, oleic acid, and linoleic acid, which are essential components suitable for biodiesel production. FTIR confirms the presence of FAME components by estimating the bending and stretching of functional groups.
Fisheries and Aquaculture Journal
The use of high protein microalgae obtained by increasing the content of nitrate in the culture medium is recommended to improve the performance of broodstock, larvae and juveniles in bivalve hatchery. However, the effect of these concentrations of nitrate on the composition of fatty acids in microalgae is not known and it is relevant to assess possible changes in its nutritional properties for filtering bivalves. The results of nitrate increase in Isochrysis aff. galbana (clone T-Iso) showed that in the high nitrate medium, T-Iso is high in protein and carbohydrate and low in ash, and also exhibits higher values of polyunsaturated fatty acids (PUFA), especially n-3PUFA. The best culture medium for Tetraselmis suecica would also be the one high in nitrate because of it is high in protein and lipid and low in ash, although the best values PUFA were observed in the standard nitrate medium. T-Iso was characterized by its tendency to increase the level of n-3 PUFA with the increase of nitrate, while T.suecica was characterized by no effect of nitrate on the contents of n-3 PUFA of the cells nor a PUFA pattern related to the increase or decrease of nitrate.