Non-polar Lipid Content Research Articles

Expression of glycerol-3-phosphate acyltransferase increases non-polar lipid accumulation in Nannochloropsis oceanica

Microalgae are considered a suitable production platform for high-value lipids and oleochemicals. Several species including Nannochloropsis oceanica produce large amounts of essential omega-3 polyunsaturated fatty acids (PUFAs) which are integral components of food and feed and have been associated with health-promoting effects. N. oceanica can further accumulate high contents of non-polar lipids with chemical properties that render them a potential replacement for plant oils such as palm oil. However, biomass and lipid productivities obtained with microalgae need to be improved to reach commercial feasibility. Genetic engineering can improve biomass and lipid productivities, for instance by increasing carbon flux to lipids. Here, we report the overexpression of glycerol-3-phosphate acyltransferase (GPAT) in N. oceanica during favorable growth conditions as a strategy to increase non-polar lipid content. Transformants overproducing either an endogenous (NoGPAT) or a heterologous (Acutodesmus obliquus GPAT) GPAT enzyme targeted to the endoplasmic reticulum had up to 42% and 51% increased non-polar lipid contents, respectively, compared to the wild type. Biomass productivities of transformant strains were not substantially impaired, resulting in lipid productivities that were increased by up to 37% and 42% for NoGPAT and AoGPAT transformants, respectively. When exposed to nutrient stress, transformants and wild type had similar lipid contents, suggesting that GPAT enzyme exerts strong flux control on lipid synthesis in N. oceanica under favorable growth conditions. NoGPAT transformants further accumulated PUFAs in non-polar lipids, reaching a total of 6.8% PUFAs per biomass, an increase of 24% relative to the wild type. Overall, our results indicate that GPAT is an interesting target for engineering of lipid metabolism in microalgae, in order to improve non-polar lipid and PUFAs accumulation in microalgae.

Evaluation of genotype-environment interactions for non-polar lipids and fatty acids in chickpea (Cicer arietinum L.) seeds

Genotype-environment (G × E) interactions for non-polar lipids and fatty acids were studied in 28 chickpea accessions. The total nonpolar lipid content was determined by Soxhlet procedure; fatty acid profiles were investigated by gas chromatography. There were strong negative correlations between oleic and linoleic acids and between oleic and linolenic acids. The correlation between linoleic and linolenic acids was positive and either strong or moderate. Correlations between the other acids were differently directed and of various strengths. Line Luh 99/11 turned out to be an outlier in relation to the other genotypes due to an unusually high content of stearic acid. Cultivar CDC Jade was an outlier because of too low content of stearic acid and too high content of linoleic acid. Accession UD0502195 was an outlier due to a higher content of palmitic acid. Accessions UD0500022 and UD0502195 were outliers due to the low content of total nonpolar lipids. The variability in the total nonpolar lipid content was not affected by the environment, but the environment contributions to the variability of oleic and linoleic acids were very high. There were only statistically significant differences in the oleic and linoleic acid amounts between the cultivation years. There was a positive correlation between the oleic acid content and the average air temperature during the “anthesis – maturity” period and a negative correlation between the linoleic acid content and the average temperature during this period. There was also a negative correlation between the oleic acid content and precipitation during the “anthesis – maturity” period and a positive correlation between the linoleic acid content and precipitation during this period. The palmitic acid content was the most responsive to environmental changes in cultivar CDC Vanguard and the most resistant in cultivar Krasnokutskiy 123. The stearic acid content was the most sensitive to environmental changes in cultivar ILC 3279 and the most irresponsive in accession UKR001:0502116. As to oleic and linoleic acids, line L 273-18 had the bi (plasticity) and S2di (stability) values coupled with the corresponding mean contents, meaning that this genotype may be adapted to decreased temperature. The ecovalence values (Wi2) for the total nonpolar lipids, palmitic, stearic and linolenic acids indicated that these characteristics were little responsive to environmental fluctuations. As to oleic and linoleic acids, Wi2 values were much higher in many accessions, confirming the variability of these parameters depending on growing conditions. Having the highest Wi2 values, accession Garbanzo 2 is expected to show high degrees of the G × E interactions for oleic and linoleic acids. S2di was positively correlated with Wi2.

Combined effect of CO2 concentration and low-cost urea repletion/starvation in Chlorella vulgaris for ameliorating growth metrics, total and non-polar lipid accumulation and fatty acid composition

Different CO2 concentration such as 0.03, 5, 10 and 15% and low-cost urea repletion/starvation in Chlorella vulgaris on growth, total and non-polar lipid content and fatty acid composition was studied. Chlorella vulgaris grown at 0.03% CO2 apparently revealed inferior biomass yield 0.55 g/L on 14th day compared to CO2 supplemented cells. In the case of CO2 supply, 15% CO2 has unveiled higher biomass yield at about 1.83 g/L on day 12 whereas biomass yield for 5 and 10% CO2 supplemented cells was 1.61 and 1.73 g/L, respectively on 12th day of cultivation. The biomass productivity (g) per liter per day was 32 mg in control condition whereas it was 125, 134 and 144 mg/L/d in 5, 10 and 15% CO2 supplied cells, respectively. Lipid content of the strain grown at control, 5, 10 and 15% CO2 was 21.2, 22.1, 23.4 and 24.6%, respectively and however, without CO2 addition in low-cost urea repleted and urea depleted medium grown cells revealed 21.2 and 24.2%, respectively. Interestingly, strain grown at 15% CO2 supply in urea deplete medium yielded 28.7% lipid and contribution of non-polar lipids in total lipids is 69.7%. Further, the fatty acid composition of the strain grown in 15% CO2 supply in urea depleted medium showed C16:0, C16:1, C18:1 and C18:3 in the level of 30.12, 9.98, 23.43, and 11.97%, respectively compared to control and urea amended condition.

Carbon:nitrogen ratio as a proxy for tissue nonpolar lipid content and condition in black sea bass Centropristis striata along the Middle Atlantic Bight

Spatial and temporal variability in fish tissue lipid content may reflect resource availability, reproductive or maturity state, or environmental suitability. Here, we analyzed nonpolar (storage) lipid and morphometric condition indices of black sea bass (Centropristis striata) collected from coastal waters of the Northwest Atlantic Ocean from New Jersey to North Carolina, USA. We hypothesized that the elemental ratio of carbon to nitrogen (C:N) within C. striata white muscle and liver tissue would be a robust proxy for nonpolar lipid content (NPLC) and that NPLC would predictably covary with traditional condition indices. Further, we analyzed our NPLC tissue indices to determine how regional and biological patterns in muscle and liver NPLC aligned with traditional condition indices. Our results indicated that muscle tissue NPLC was low compared to liver tissue, and regression analysis revealed strong positive relationships between C:N and NPLC for both tissues (muscle—best fit was linear; liver—best fit was asymptotic nonlinear). Correlations of muscle and liver NPLC with other condition indices were index and region dependent (e.g., a reproductive index was positively correlated with muscle NPLC, but negatively correlated with liver NPLC). Tissue NPLC and standard condition indices differed significantly as a function of region, sex, and fish length, although the patterns were not consistent across the different indices. Our results support the use of muscle and liver C:N values to estimate tissue-specific C. striata NPLC. Further, our results indicate that NPLC indices provide additional insight into C. striata physiological condition and could assist studies examining habitat suitability across large spatial or temporal scales.

Energy recovery in high rate algal pond used for domestic wastewater treatment

High rate algal pond (HRAP) was evaluated according to its energy potential and productivity by two rates, net energy ratio (NER) and specific biomass productivity. All energy inputs were calculated according to one HRAP with pre-ultraviolet disinfection treating anaerobic domestic sewage. The outputs were calculated for two energetic pathways: lipid and biogas production for the raw biomass (RB) and biomass after lipid extraction. The non-polar lipid content in dry biomass was 7.6%, reaching a daily lipid productivity of 0.2 g/m2·day and the biogas production potential was 0.20 m3/kg solids. For the biomass after lipid extraction, the biogas production reached 2.6 m3/kg solids. NER values of 10-3 for the RB were similar for lipids and biogas routes. The specific biomass productivity was 0.7 mg/kJ. For the residual biomass, after lipid extraction, NER value was 10-2 for the integrated route (lipids + biogas) and the specific biomass productivity of the extracted biomass was 0.4 mg/kJ. The best energetic pathway was to integrate both lipids and biogas route.

Yeast MRX deletions have short chronological life span and more triacylglycerols.

Saccharomyces cerevisiae is an excellent model organism for lipid research. Here, we have used yeast haploid RAdiation Damage (RAD) deletion strains to study life span and lipid storage patterns. RAD genes are mainly involved in DNA repair mechanism and hence, their deletions have resulted in shorter life span. Viable RAD mutants were screened for non-polar lipid content, and some of the mutants showed significantly high amounts of triacylglycerol (TAG) and steryl ester, besides short chronological life span. Among these, RAD50, MRE11 and XRS2 form a complex, MRX that is involved in homologous recombination that showed an increase in the amount of TAG. Microarray data of single MRX deletions revealed that besides DNA damage signature genes, lipid metabolism genes are also differentially expressed. Lipid biosynthetic genes (LPP1, SLC1) were upregulated and lipid hydrolytic gene (TGL3) was downregulated. We observed that rad50Δ, mre11Δ, xrs2Δ and mrxΔ strains have high number of lipid droplets (LDs) with fragmented mitochondria. These mutants have a short chronological life span compared to wild type. Aged wild-type cells also accumulated TAG with LDs of ∼2.0 μm in diameter. These results suggest that TAG accumulation and big size LDs could be possible markers for premature or normal aging.

Sexual Dimorphisms in Metabolism, Organ Mass, and Reproductive Energetics in Pre-breeding American Toads (Anaxyrus americanus)

Sexual size dimorphisms are common in many species of anurans, and have often been ascribed to different selective forces that influence reproductive success in males and females. However, less is known about dimorphisms in whole-organism physiology or in internal morphology in anurans. In this study, we investigated potential differences in metabolism, visceral organ mass, and stored energy content between male and female American Toads (Anaxyrus americanus) collected en route to breeding areas during the spring. Female toads were both longer and more massive than males. Males demonstrated larger increases in metabolic rate, heart mass, liver mass, and nonpolar lipid content with increasing body size than did females, but kidney mass did not differ between the sexes. The ovaries of the females represented, on average, 38% of the total dry mass and 54% of the total caloric energy contained in their bodies. However, the body-size adjusted caloric content of the carcass did not differ between males and females. Our findings suggest that larger males are physiologically able to support greater levels of activity during the breeding season and thus will more likely engage in more strenuous activities such as calling, active seeking of females, and amplexus interference, compared to smaller males. Large females, on the other hand, appear to preferentially allocate resources to oogenesis. In addition, our findings suggest that although the overall energetic cost of reproduction may be greater for females, there may be other energetic constraints within or outside of the reproductive period that limit the ability of males to allocate resources to growth and storage.

Fatty acid profile ofPleurotus ostreatusandGanoderma australegrown naturally and in a batch bioreactor

Non-polar lipid content and fatty acid (FA) composition of the commercial edible strain of Pleurotus ostreatus and the medicinal wild strain of Ganoderma australe were determined. A comparison of the FA profile was conducted between mycelium grown under optimum bioreactor conditions and naturally occurring fruit bodies in both species. Both strains contained unsaturated FA (UFA), amounting to 55–77% of total FA content, whereas the proportion of essential FA was contributive, permitting their consideration as potential food ingredients. Bioreactor process resulted in a significant total FA content increase accompanied with a considerable effect on ratios of nutritional interest (MUFA/SFA, PUFA/SFA, oleic/linoleic).

염분농도에 따른 해양미세조류(Nannochloropsis oculata)의 지질 및 지방산의 변화

The quality and quantity of food organisms in fish seed production are important. The marine microalgae Nannochloropsis oculata are used as initial food organisms in the field. We investigated the effects of salinity (0, 10, 20, 30, 40 and 50 psu) on the lipid and fatty acid composition of N. oculata. Cultivation of N. oculata at varying salinities showed the highest growth rate at 20 psu. Total lipid content ranged from 17.26 to 18.63% at salinities from 0 to 50 psu). The nonpolar lipid content increased markedly at 30 psu and was highest at 15.55%. The polar lipid content was lowest at 30 psu, by 84.45%. It was also found that the omega-3 and EPA contents were inversely proportional to salt concentration. For the polar and nonpolar lipid compositions, there was no significant effect of salinity. Omega-3 polyunsaturated fatty acid content especially the content of EPA in the seawater larvae is the essential fatty acid in this food organism. It is thus advantageous to culture N. oculata at 20 psu.

Bioenergetic effects of aqueous copper and cadmium on the grass shrimp, Palaemonetes pugio

Adult grass shrimp ( Palaemonetes pugio) were exposed to either aqueous copper (ranging from 7.54 to 41.29 μg Cu 2+/L) or cadmium (2.48– 6.55 μg Cd 2+/L) for 14 days in laboratory experiments to quantify effects on survival and bioenergetic processes, including respiration, somatic growth, energy (lipid) storage, and food consumption. The lowest observed effect concentrations for mortality were 41.29 μg Cu 2+/L or 6.55 μg Cd 2+/L, expressed as free metal ion concentrations. Both copper and cadmium caused a decrease in respiration rate at concentrations of 7.54 to 41.29 μg Cu 2+/L or 6.55 μg Cd 2+/L. Exposure to copper (≥ 27.03 μg Cu 2+/L) resulted in negative somatic growth (i.e., weight loss). Cadmium exposure (6.17 μg Cd 2+/L) caused a decrease in growth rate, relative to the control, but growth remained positive. Nonpolar lipid content and food consumption were not significantly affected by exposure to either copper or cadmium. Our results suggest that both copper and cadmium result in overall metabolic depression, decreasing energy allocation to both maintenance and production.

Fatty acid profiles of polar and non-polar lipids of Pleurotus ostreatus and P. cornucopiae var. ‘ citrino-pileatus’ grown at different temperatures

The application of fatty acid (FA) composition data has now extended to studies of physiology, chemotaxonomy, and intrageneric differentiation, as well as to studies of human nutrition. Environmental factors such as nutritional components, oxygen, and temperature are known to affect lipid content and composition in living organisms, including fungi. In the present study, the polar and non-polar lipid content of Pleurotus ostreatus and P. cornucopiae var. citrino-pileatus fruiting bodies produced at temperatures ranging from 12–27 °C and from 17–27 °C, respectively, were analysed to evaluate the effect of temperature on lipid composition in these mushrooms. Results showed that lowering the growth temperature below 17 °C generally provided an expected increase in FA unsaturation in polar and non-polar lipids of P. ostreatus. Although raising the temperature above 17 °C did not show any clear-cut tendency in FA unsaturation, it did reveal that growth temperature had a differential effect on the FA profiles in fruiting bodies of P. ostreatus and P. cornucopiae. This study suggests that care should be taken when using FA content and unsaturation data for physiological, chemotaxonomic, and intrageneric differentiation studies, and that it may be possible to manipulate lipid unsaturation in Pleurotus spp. through modified growth temperatures.

Fatty acid composition of lipids from mushrooms belonging to the family Boletaceae

The non-polar lipid content and fatty acid (FA) composition of 11 mushroom species of the family Boletaceae were determined. The non-polar lipid content ranged from 2.0 ( Leccinum aurantiacum and Boletus erythropus) to 5.4 % (w/w) d.w. ( Suillus grevillei) with an average value of 2.9 %. More than 25 different FAs were found in the mushroom lipids. Unsaturated FAs, mainly linoleic and oleic acids, accounted for about 83 % of the total FAs, while palmitic acid was the main saturated FA. Some FAs are identified for the first time in Boletaceae and in higher Basidiomycetes ( cis-11,12-methyleneoctadecanoic acid, 7- cis,10- cis hexadecadienoic) or in fungi ( cis-11,12-methyleneoctadecanoic acid). There were significant differences ( P < 0.05) in the contents of specific FAs between mushroom species.

Distribution of free lipids and their fractions in wheat flour milled streams

Polar and non-polar lipids both play an important role in determining the quality of wheat flour and its suitability for different bakery products. In order to develop specific flours for different end-uses, polar and non-polar lipid content were determined in streams and both showed wide variation. The total free non-polar lipid (TFNPL) content varied from 0.54 to 1.8% (db) while total free polar lipid (TFPL) content varied from 0.11 to 0.34% (db) in different flour streams indicating the preponderance of TFNPL. Triglycerides were the predominant fraction present in TFNPL while glycolipids predominated in the TFPL fraction. The amounts of these fractions were greater in the IV break stream. In the case of saturated fatty acids, palmitic acid was predominant in TFNPL fractions, whereas, stearic acid was predominant in TFPL. The levels of oleic acid were higher in TFNPL (16.9 to 33.6%). Linoleic acid was the predominant unsaturated fatty acid in both TFNPL and TFPL fractions.

Effects of trans fatty acids on lipid accumulation in 3T3-L1 cells.

Previous work had shown that dietary trans fatty acids (tFA) resulted in decreased fat deposition in adipose tissue. This study was conducted to see if tFA influence lipid accumulation in Swiss mouse fibroblast 3T3-L1 cells, which are widely used as an adipocyte model. Cells were cultured in the presence of experimental or control growth media supplemented with fatty acids complexed to bovine serum albumin. Fatty acid compositions of experimental and control growth media were similar except that the octadecenoates in the control growth media were cis fatty acids, whereas those in the experimental media contained both cis and trans fatty acids. Cell-conditioned media and cellular lipids at the preadipocyte and differentiating adipocyte stages were analyzed. At both stages of development, less fat accumulated in cells cultured in the presence of tFA, due primarily to a decrease in the nonpolar lipid content of cells exposed to tFA, and linoleate to arachidonate ratios were higher in cells supplemented with tFA. Calculations comparing sums of saturated and monounsaturated fatty acids in cells at the differentiating adipocyte stage suggested that tFA may have replaced monounsaturated fatty acids in the nonpolar lipid fraction and saturated fatty acids in the polar lipid fraction. The results of these studies are in good agreement with the in vivo effects of tFA seen in previous work with mouse adipose tissue. It was concluded that the 3T3-L1 in vitro model is an appropriate system for further studies of tFA and lipid metabolism in adipose tissue.

Interaction of bovine serum high density lipoprotein with mixed vesicles of phosphatidylcholine and cholesterol.

The interaction of sonicated, small vesicles of egg phosphatidylcholine and cholesterol (2:1, mol/mol) with bovine high density serum lipoproteins was examined in terms of lipid transfer between both types of particles and the resulting changes in lipoprotein structure. Saturation of high density lipoprotein preparations with vesicle lipids gave final lipoprotein particles with essentially unchanged protein content and composition, unchanged cholesterylester and nonpolar lipid content, but with markedly increased phospholipid content (59% increas by weight) and moderately increased cholesterol content (20% increase by weight). The lipoproteins enriched in lipid were relatively uniform, spherical particles, 110 +/- 3.6 A in diameter (6 A larger than the original lipoproteins); they had a markedly decreased intrinsic protein fluorescence, a red-shifted fluorescence wavelength maximum, and more fluid lipid domains. These results indicate that the direct addition of excess lipids from membranes or other lipoproteins is a possible mechanism for lipid transfer to high density lipoproteins. Also they suggest a structural flexibility of high density lipoproteins that allows the addition of significant amounts of surface components.