High temperature enhances lipid accumulation in nitrogen-deprived <Emphasis Type="Italic">Scenedesmus obtusus</Emphasis> XJ-15

This study investigated the changes in lipid and starch contents, lipid fraction, and lipid profile in the nitrogen-starved Scenedesmus obtusus XJ-15 at different temperatures (17, 25, and 33 °C). The optimal temperature for both growth and lipid accumulation under nitrogen-sufficient condition was found to be 25 °C. However, under nitrogen deprivation, the total and neutral lipids increased with increasing temperature, and achieved the highest lipid content of 47.60 % of dry cell weight and the highest TAG content of 79.66 % of total lipid at 33 °C. In the meantime, the stored cellular starch content decreased with the increasing temperature. Thus, high temperature induced carbon flux from starch toward TAG accumulation in microalgae during nitrogen starvation. In addition, the decreased polar lipids may also serve for TAG synthesis under high temperature, and high temperature further reduced the degree of the fatty acid unsaturation and favored a better biodiesel production. These results suggested that high-temperature stress can be a good strategy for enhancing biofuel production in oleaginous microalgae during nitrogen deficiency.     

Influences of Culture Temperature on the Growth, Lipid Content and Fatty Acid Composition of Aurantiochytrium sp. Strain mh0186

The growth, lipid content, and fatty acid composition of Aurantiochytrium sp. strain mh0186 at different temperatures were investigated. Strain mh0186 grew well at 15–30°C, but weakly at 10°C. The biomass at 15–30°C was significantly higher than at 10 and 35°C, and the total lipid at 15–35°C was significantly higher than that at 10°C. The amount of DHA in the total fatty acid was highest at 10°C and decreased in response to temperature increase. The content of DHA (mg/g-dry cell weight) at 15–30°C were significantly higher than those at 35°C and those at 15–25°C were significantly higher than those at 10 and 35°C. The DHA yield at 15–35°C was significantly higher than those at 10 and 35°C. Unsaturation of fatty acid was regulated by temperature and was enhanced in response to temperature decrease. The ratio of DHA to DPA varied at different temperatures.     

At high temperature lipid production in Ettlia oleoabundans occurs before nitrate depletion

Temperature and light intensity effects on biomass and lipid production were investigated in Ettlia oleoabundans to better understand some fundamental properties of this potentially useful but poorly studied microalgal species. E. oleoabundans entered dormant state at 5 °C, showed growth at 10 °C, and when exposed to light at 70 μmol photons per square meter per second at 10 °C, cells reached a biomass concentration of >2.0 g?L^?1 with fatty acid methyl esters of 11.5 mg?L^?1. Highest biomass productivity was at 15 °C and 25 °C regardless of light intensity, and accumulation of intracellular lipids was stimulated by nitrate depletion under these conditions. Although growth was inhibited at 35 °C, at 130 μmol photons per square meter per second lipid content reached 10.37 mg?L^?1 with fatty acid content more favorable to biodiesel dominating; this occurred without nitrate depletion. In a two-phase temperature shift experiment at two nitrate levels, cells were shifted after 21 days at 15 °C to 35 °C for 8 days. Although after the shift growth continued, lipid productivity per cell was less than that in the 35 °C cultures, again without nitrate depletion. This study showed that E. oleoabundans grows well at low temperature and light intensity, and high temperature can be a useful trigger for lipid accumulation independent of nitrate depletion. This will prove useful for improving our knowledge about lipid production in this and other oleaginous algae for modifying yield and quality of algal lipids being considered for biodiesel production.     

Lack of UCP1 stimulates fatty liver but mediates UCP1-independent action of beige fat to improve hyperlipidemia in Apoe knockout mice

Brown adipose tissue (BAT) plays a critical role in lipid metabolism and may protect from hyperlipidemia; however, its beneficial effect appears to depend on the ambient temperature of the environment. In this study, we investigated the effects of uncoupling protein 1 (UCP1) deficiency on lipid metabolism, including the pathophysiology of hyperlipidemia, in apolipoprotein E knockout (APOE-KO) mice at a normal (23 °C) and thermoneutral (30 °C) temperature. Unexpectedly, UCP1 deficiency caused improvements in hyperlipidemia, atherosclerosis, and glucose metabolism, regardless of an increase in hepatic lipid deposition, in Ucp1/Apoe double-knockout (DKO) mice fed a high-fat diet at 23 °C, with BAT hyperplasia and robust browning of inguinal white adipose tissue (IWAT) observed. Proteomics and gene expression analyses revealed significant increases in many proteins involved in energy metabolism and strong upregulation of brown/beige adipocyte-related genes and fatty acid metabolism-related genes in browned IWAT, suggesting an induction of beige fat formation and stimulation of lipid metabolism in DKO mice at 23 °C. Conversely, mRNA levels of fatty acid oxidation-related genes decreased in the liver of DKO mice. The favorable phenotypic changes were lost at 30 °C, with BAT whitening and disappearance of IWAT browning, while fatty liver further deteriorated in DKO mice compared with that in APOE-KO mice. Finally, longevity analysis revealed a significant lifespan extension of DKO mice compared with that of APOE-KO mice at 23 °C. Irrespective of the fundamental role of UCP1 thermogenesis, our results highlight the importance of beige fat for the improvement of hyperlipidemia and longevity under the atherogenic status at normal room temperature.     

Optimization of environmental parameters for <Emphasis Type="Italic">Nannochloropsis salina</Emphasis> growth and lipid content using the response surface method and invading organisms

Algae biofuel has the potential to replace fossil fuels. However, cultivation and productivity of target algae need improvement, while controlling undesired organisms that can lower the efficiency of production systems. A central composite design and response surface model were utilized to predict cultivation optima of marine microalga, Nannochloropsis salina, under a suite of environmental parameters. The effects of salinity, pH, and temperature and their interactions were studied on maximum sustainable yield (MSY, a measure for biomass productivity), lipid content of N. salina, and invading organisms. Five different levels of each environmental predictor variable were tested. The environmental factors were kept within ranges that had previously been determined to allow positive N. salina growth (14.5–45.5 PSU; pH 6.3–9.7; 11–29 °C). The models created for this experiment showed that N. salina’s MSY and lipid content are not strongly affected over the broad range of salinity and temperature values. Calculated optima levels were 28 PSU/20 °C for MSY and 14.5 PSU/20 °C for lipid accumulation, but neither value significantly influenced the model. However, pH was the most important factor to influence algae productivity, and pH optimum was estimated around 8. Both MSY and lipid content were strongly reduced when pH deviated from the optimum. Occurrence of invading organisms seemed stochastic, and none of the environmental factors studied significantly influenced abundance. In conclusion, pH should be kept around 8 for maximum productivity of N. salina. Temperature and salinity should be kept around 20 °C and 28 PSU; however, moderate variations are not too much of a concern and might enhance lipid content of N. salina.     

Biosynthesis of lipids by Rhodosporidium toruloides ATCC 10788

The limiting amount of nitrogen required to trigger lipid accumulation in the oleaginous yeast Rhodosporidium toruloides ATCC 10788 was studied, batchwise, by subjecting washed mid-exponentially grown cells to nitrogen at levels of 10⁻² M down to 10⁻⁴ M per g l⁻¹ of lean cells (2–5% fat content) in a mineral medium where glucose was present at 35 g l⁻¹. The results showed that lipid accumulation always started sometime after nitrogen reached a level of 3 × 10⁻⁵ M and the specific initial lipid productivity was constant. Furthermore, the cells were subjected to nine combinations of temperature and pH, from (25° C, pH 4.5) to (35° C, pH 7.5) in the mineral medium supplemented with 0.5 g l⁻¹ of yeast extract and 1 g l⁻¹ (NH₄)₂SO₄. As was expected, lipid content in the cells was higher at 25° C, but pH around 6.0–7.5 slightly enhanced the effect of lower temperature. The effect of pH was also noticed to affect the size of changes in the temporal profiles of the oil's fatty acid distribution prior to nitrogen depletion, whereas no significant difference in the fatty acid composition of the oil was shown after exhaustion of nitrogen from the medium for all combinations of temperature and pH.     

Changes of lipid content and fatty acid composition of Schizochytrium limacinum in response to different temperatures and salinities

The growth, lipid content and fatty acid composition of Schizochytrium limacinum OUC88 at different temperatures (16, 23, 30 and 37 °C) and salinities (0, 0.9, 1.8, 2.7 and 3.6%, w/v) were analyzed. The strain grew better and lipid contents were higher at 16–30 °C and salinity at 0.9–3.6% (w/v). The adaptive responses of this microbe to temperature and salinity were mainly to regulate the degree of fatty acid unstauration to maintain the normal membrane lipid physical state. However, at 37 °C and 0 salinity, the growth of the strain was inhibited obviously and the lipid content reduced significantly and, some important changes occurred in fatty acid composition, especially the odd-numbered fatty acids 15:0 and 17:0 which amounts increased greatly. In addition, the ratio of DHA to DPA changed at different temperatures and salinities.     

Effects of l-leucine in ovo feeding on thermotolerance,growth and amino acid metabolism under heat stress in broilers

Recently, we found that in ovo feeding of l-leucine (l-Leu) afforded thermotolerance, stimulated lipid metabolism and modified amino acid metabolism in male broiler chicks. However, the effects of in ovo feeding of l-Leu on thermoregulation and growth performance until marketing age of broilers are still unknown. In this study, we investigated the effects of in ovo feeding of l-Leu on body weight (BW) gain under control thermoneutral temperature or chronic heat stress. We measured changes of body temperature and food intake, organ weight, as well as amino acid metabolism and plasma metabolites under acute and chronic heat stress in broilers. A total of 168 fertilized Chunky broiler eggs were randomly divided into 2 treatment groups in experiments. The eggs were in ovo fed with l-Leu (34.5 µmol/500 µl per egg) or sterile water (500 µl/egg) during incubation. After hatching, male broilers were selected and assigned seven to nine replicates (one bird/replicate) in each group for heat challenge experiments. Broilers (29- or 30-day-old) were exposed to acute heat stress (30 ± 1°C) for 120 min or a chronic heat cyclic and continued heat stress (over 30 ± 1°C; ages, 15 to 44 days). In ovo feeding of l-Leu caused a significant suppression of enhanced body temperature without affecting food intake, plasma triacylglycerol, non-esterified fatty acids, ketone bodies, glucose, lactic acid or thyroid hormones under acute heat stress. Daily body temperature was significantly increased by l-Leu in ovo feeding under chronic heat stress. Interestingly, in ovo feeding of l-Leu caused a significantly higher daily BW gain compared with that of the control group under chronic heat stress. Moreover, some essential amino acids, including Leu and isoleucine, were significantly increased in the liver and decreased in the plasma by l-Leu in ovo feeding under acute heat stress. These results suggested that l-Leu in ovo feeding afforded thermotolerance to broilers under acute heat stress mainly through changing amino acid metabolism until marketing age.     

Effect of temperature on fatty acid composition and development of unfed Siberian sturgeon (A. baerii) larvae

The fatty acid metabolism in fish is influenced by various factors, including fish species, water temperature, water environment and diet supply. The aim of present work is to investigate the fatty acid composition of yolk‐stage Siberian sturgeon larvae reared at three different temperatures. Fertilized Siberian sturgeon eggs were transferred to the Lodi Aquaculture Research Center of the University of Milan, divided in three aquaria, each containing three incubators and incubated at 16°C. After hatching the temperature was switched to 16, 19 and 22°C. Larvae sampling was performed at the end of yolk sac reabsorption. No feed was dispensed during the trial. Eggs and larvae were weighed and fatty acid profile was determined by GC‐FID analysis after lipid extraction by chloroform/methanol mixture and fatty acid transesterification by methanolic hydrogen chloride. The fertilized eggs had a weight of 23.27 mg and a lipid content of 2.67 mg/egg. At hatching, the weight was 12.2 (0.17 SD) mg and lipid content 1.9 (0.6 SD) mg/larva. At the end of the trial, larvae mean weight was 33.6 (3.6 SD), 34.7 (1.8 SD) and 36.9 (1.1 SD) mg, while lipid content was 2.0 (0.3 SD), 2.1 (0.3 SD) and 2.0 (0.2 SD) mg for larvae reared at 16, 19 and 22°C respectively, without statistically significant difference. Larvae subjected to the highest water temperature showed a faster yolk‐sac absorption. No differences were found across temperatures regarding survival rates and regarding ontogenic development. The fatty acid composition of larvae was affected by the temperature. Larvae reared at 16°C had the lowest amount of saturated fatty acids, mainly due to a lower palmitic acid content, that was offset by a higher level of linolenic and linoleic acid, if compared with larvae reared at 19°C and 22°C. The study suggests that at a lower temperature sturgeon spare unsaturated fatty acid consuming preferably saturated fatty acids, increasing our knowledge of the fatty acid metabolism in this species.     

Heat Shock Induced Lipid Changes and Solute Leakage in Germinating Seeds of Pigeonpea

Heat shock (HS) reduced total lipid and phospholipid contents and their synthesis in germinating seeds of pigeonpea [Cajanus cajan (L.) Millspaugh]. Lipid peroxidation was also enhanced with increasing temperature and HS duration. HS influenced lipid metabolism to a higher extent at 45°C than at 40°C. This altered lipid metabolism and lipid peroxidation was associated with the loss of various solutes from the germinating seeds, and modification of growth and development. Pretreatment of germinating seeds at 40°C for 1 h or at 45°C for 10 min followed by incubation at 28°C for 3 h prior to 45°C for 2 h ameliorated solute leakage due to reduced lipid peroxidation and improvement in lipid content and membrane function.     

Decrease in sunflower (Helianthus annuus) seed viability caused by high temperature as related to energy metabolism, membrane damage and lipid composition

The aim of the present work was to investigate whether loss of germination ability and viability of sunflower (Helianthus annuus L.) seeds during incubation at a high temperature (45°C) was related to changes in energy metabolism, loss of membrane integrity, and/or changes in lipid composition. Pre‐treatment of seeds at 45°C progressively reduced subsequent germination at the optimal temperature (25°C). Seeds did not germinate at 45°C and almost all of them were dead after 72 h of soaking at this high temperature. This loss of seed viability was associated with a large increase in leakage of K⁺ and total electrolytes into the incubation medium, and with production of malondialdehyde in the embryonic axis and cotyledons, suggesting a loss of membrane integrity probably due to lipid peroxidation. ATP and ADP levels increased sharply during the first hours of imbibition at 45°C, remained high for about 24 h and then decreased. As a consequence, the energy charge followed a similar pattern. If the treatment at 45°C did not exceed 48 h, seeds recovered an apparently normal energy metabolism after transfer to 25°C, even though they lost their ability to germinate at this temperature. Therefore, energy metabolism at the whole embryo level cannot be considered as an indicator of germination ability. Incubation of seeds at 45°C resulted in an increase in triacylglycerols and diacylglycerols without a significant change in their fatty acid composition. It also induced a slight increase in phospholipid content with an increase in C_16:0, C_18:0 and C_18:1, but with no change in C_18:2. In phospholipids, the C_18:2/C_18:1 and (C_18:1 + C_18:2)/ (C_16:0 + C_18:0) ratios thus declined during treatment at 45°C. The results obtained suggest that deterioration of sunflower seeds during incubation at a high temperature is mainly related to membrane damage and alteration of energy metabolism, and that accumulation of malondialdehyde, which is an index of lipid peroxidation, does not correspond to a decrease in total lipids and phospholipids nor to a significant change in fatty acid composition, except in PL in which the C_18:2/C_18:1 and (C_18:1 + C_18:2)/ (C_16:0 + C_18:0) ratios slightly declined.     

The in vitro effect of temperature on motility and antioxidant response of common carp Cyprinus carpio spermatozoa

The effect of temperature on Cyprinus carpio spermatozoa in vitro was investigated with spermatozoa activated at 4, 14, and 24 °C. At 30 s post-activation, motility rate was significantly higher at 4 °C compared to 14 and 24 °C, whereas highest swimming velocity was observed at 14 °C. The thiobarbituric acid-reactive substance (TBARS) content was significantly higher at 14 °C and 24 °C than at 4 °C in motile spermatozoa. No significant differences in catalase and superoxide dismutase activity relative to temperature were observed. This study provides new information regarding effect of temperature on lipid peroxidation intensity and spermatozoon motility parameters in carp. The elevation of TBARS seen at higher temperatures could be due to inadequate capacity of antioxidant enzymes to protect the cell against the detrimental effects of oxidative stress induced by higher temperatures.     

Temperature-induced changes of malondialdehyde, heat-shock proteins in relation to chlorophyll fluorescence and photosynthesis in Conocarpus lancifolius (Engl.)

The effect of variable temperatures (10–50 °C) on photosynthesis and chlorophyll fluorescence in Conocarpus lancifolius was evaluated. Additionally, the ability of the species to synthesize heat-shock proteins (HSPs) to protect against high temperatures, and malondialdehyde (MDA) as a by-product of lipid peroxidation was investigated. Plants at 10 °C showed virtually no measurable growth, leaf discoloration and a few brown lesions, while high temperatures (40 and 50 °C) promoted growth and lateral branch development. Chlorophyll content index, photochemical efficiency (F _v/F _m) of PS II, electron transport rate and photosynthetic rate declined with decreasing temperature but increased significantly at higher temperatures. Heat-shock protein (HSP 70 kDa) was produced at temperatures 30–50 °C and an additional 90 kDa protein was also produced at 50 °C. Increase in the efficiency of excitation energy captured by the open PS II reaction centers (F _v/F _m) increased linearly (P ≤ 0.05) with the accumulation of HSP 70 at higher temperatures. However, at low temperatures the concentration of MDA increased significantly, indicating lipid peroxidation due to oxidative stress. The production and accumulation of HSP 70 and 90 kDa coupled with increased electron transport rate and photochemical efficiency can be used to assess survival, growth capacity and to some extent the tolerance of C. lancifolius to elevated temperatures.     

Differential temperature effect on the production of enhanced gamma linolenic acid in <Emphasis Type="Italic">Mucor rouxii</Emphasis> CFR-G15

Mucor rouxii CFR-G15, a locally isolated phycomycetous fungus, on cultivation at room temperature produced more than 30% (w/w) lipid in their dry cell weight, in which 14.2% accounted to be GLA content of the total fatty acids. It was observed that when incubation temperature lowered at 14°C, GLA content of the mycelium increased significantly (P<0.05) from 14.2% to 21.97%. In order to optimize the cultural conditions for high biomass and lipid production with high GLA content, the fungus was grown in association of two different temperatures and supply of additional glucose in culture medium. Maximum lipid and GLA were obtained 23.56 and 19.5% respectively, when the culture was grown at 28°C for four days and followed by addition of glucose (5%), and lowered the incubation temperature to 14°C for another four days. The presence of GLA in the oil obtained from M. rouxii CFR-G15 was confirmed by the gas chromatography-mass spectrometry. Gamma linolenic acid (GLA, n-6) is gaining importance in pharmaceutical and nutraceutical industries because of clinical evidence demonstrated that it has various beneficial effects in human health. In this paper temperature played a major role in enhancing the GLA content which has been described.     

The effect of temperature on growth and lipid and fatty acid composition on marine microalgae used for biodiesel production

Cultivation temperature is one of the major factors affecting the growth and lipid accumulation of microalgae. In this study, the effects of temperature on the growth, lipid content, fatty acid composition and biodiesel properties of the marine microalgae Chaetoceros sp. FIKU035, Tetraselmis suecica FIKU032 and Nannochloropsis sp. FIKU036 were investigated. These species were cultured at different temperatures (25, 30, 35 and 40 °C). The results showed that the specific growth rate, biomass and lipid content of all microalgae decreased with increasing temperature. With regards to fatty acids, the presence of saturated fatty acids (SFAs) in T. suecica FIKU032 and Nannochloropsis sp. FIKU036 decreased with increasing temperature, in contrast with polyunsaturated fatty acids (PUFAs). Moreover, Chaetoceros sp. FIKU035 was the only species that could grow at 40 °C. The highest lipid productivity was observed in Chaetoceros sp. FIKU035 when cultivated at 25 °C (66.73 ± 1.34 mg L^?1 day^?1) and 30 °C (61.35 ± 2.89 mg L^?1 day^?1). Moreover, the biodiesel properties (cetane number, cold filter plugging point, kinematic viscosity and density) of the lipids obtained from this species were in accordance with biodiesel standards. This study indicated that Chaetoceros sp. FIKU035 can be considered as a suitable species for biodiesel production in outdoor cultivation.     

Overcoming the metabolic burden of protein secretion in Schizosaccharomyces pombe – A quantitative approach using 13C-based metabolic flux analysis

Protein secretion in yeast is generally associated with a burden to cellular metabolism. To investigate this metabolic burden in Schizosaccharomyces pombe, we constructed a set of strains secreting the model protein maltase in different amounts. We quantified the influence of protein secretion on the metabolism applying ¹³C-based metabolic flux analysis in chemostat cultures. Analysis of the macromolecular biomass composition revealed an increase in cellular lipid content at elevated levels of protein secretion and we observed altered metabolic fluxes in the pentose phosphate pathway, the TCA cycle, and around the pyruvate node including mitochondrial NADPH supply. Supplementing acetate to glucose or glycerol minimal media was found to improve protein secretion, accompanied by an increased cellular lipid content and carbon flux through the TCA cycle as well as increased mitochondrial NADPH production. Thus, systematic metabolic analyses can assist in identifying factors limiting protein secretion and in deriving strategies to overcome these limitations.     

Liposomes from the thermophilic eubacterium Thermus SP. fluorescence polarization and permeability properties

• 1.1. The physical properties of liposomes prepared from total and polar lipid extracts of Thermus SPS 11 and SPS 17 grown at 50°C and at the optimal growth temperature (73–75°C) have been studied using 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization (P) and correlated to the permeability properties of the bilayers.
• 2.2. P data show the presence of a broad phase transition from a gel to a liquid-crystal phase for all liposomes studied. Liposomes from lipid fractions of Thermus SPS 11 and SPS 17 grown at 50°C were in a less fluid state than those of bacteria grown at the optimal growth temperature.
• 3.3. Comparing the permeabilities to ethyleneglycol, glycerol and erythritol of liposomes from lipid extracts of Thermus SPS 11 and SPS 17 grown at the two temperatures already mentioned, liposomes from lipid extracts of bacteria grown at 50°C were, in general, more permeable to ethyleneglycol and glycerol and less permeable to erythritol.
• 4.4. Liposomes from lipid fractions with higher carotenoid (CA) content were in a more rigid state within the whole range of temperatures studied, and their permeabilities to the three polyols were significantly lower than in the low-CA samples.

     

Characterization of the main lipid components of chloroplast membranes and cold induced changes in Coffea spp.

Low temperatures affect many plant physiological and biochemical components, amongst them the lipid phase of membranes. The present work aimed to characterize the lipid composition of chloroplast membranes of three Coffea genotypes, representing three agronomic valuable species (Coffea arabica cv. Icatu, Coffea canephora cv. Conilon clone 02 and Coffea dewevrei), under adequate environmental conditions and to relate its cold tolerance ability to the adjustments triggered during a gradual temperature decrease, after chilling exposure and upon a recovery period. Under adequate temperature (25/20 °C, day/night) the lipid composition of chloroplast membranes was fairly similar amongst the genotypes concerning the total fatty acid (TFA) content and individual FAs (both globally or within the classes), suggesting a close lipid composition amongst Coffea species, which can be considered as “C18:3” plants. Under cold exposure and subsequent recovery the genotypes undergo adjustments, some of them with acclimation potential. The genotypes displayed some ability to increase lipid synthesis, increasing their FA content. However, under cold exposure (even at 4 °C), Icatu and C. dewevrei plants performed qualitative adjustments, including preferential synthesis of phospholipids (especially PG) instead of galactolipids and increases in the unsaturation degree of DGDG and phospholipid classes (PG, PC and PI). Clone 02 maintained almost all lipid characteristics, what explains its higher cold sensitivity. Furthermore, differences that contribute to explain contrasting cold sensitivity in Icatu (more tolerant) and C. dewevrei emerged when analyzing PA content (taken as a stress metabolite) and the FA composition within MGDG and PG classes. C. dewevrei presented the higher increase, absolute value and relative weight of PA, while Icatu was the solely genotype to show a rise in the unsaturation degree of MGDG and PG, displaying as well the highest DBI values for these classes. We conclude that lipid qualitative and quantitative adjustments constitute a flexible mechanism that decisively contributes to cold acclimation in Coffea spp., working in tandem with others that minimize oxidative stress damages.     

Light,temperature and nitrogen starvation effects on the total lipid and fatty acid content and composition ofSpirulina platensis UTEX 1928

The total lipid and fatty acid content ofSpirulina platensis UTEX 1928 was 7.2 and 2.2% respectively of cellular dry weight under controlled conditions supporting high growth rates. With increases in irradiance from 170 to 870 μmol photon m^?2 s^?1, growth rate increased, total lipid decreased, and fatty acid composition was unaffected. At 1411 μmol photon m^?2 s^?1, total lipid increased slightly and percent composition of the fatty acid gamma linolenic acid increased. Growth and total lipid content ofS. platensis were affected by changes in growth temperature from 25 to 38 °C. With increased growth rate, total lipid content increased. This suggests that the storage of carbon increases at temperatures supporting high growth rates. The degree of saturation increased with temperature. Although the percent composition of gamma linolenic acid was higher at lower growth temperature, production was still primarily a function of growth rate. The effect of temperature on fatty acid content and degree of saturation was of secondary importance. Nitrogen starvation increased total lipid content but decreased fatty acid content as a percentage of dry weight; composition of the fatty acids was unaffected. N-starvation appeared to suspend synthesis of long chain fatty acids inS. platensis, suggesting that some other compound stores fixed carbon when nitrogen is limiting. It was concluded that fatty acid production inS. platensis is maximized by optimizing culture conditions for growth.