Storage lipid accumulation and acyltransferase action in developing flaxseed

Investigations of storage lipid synthesis in developing flaxseed (Linum usitatissimum) provide useful information for designing strategies to enhance the oil content and nutritional value of this crop. Lipid content and changes in the FA composition during seed development were examined in two cultivars of flax (AC Emerson and Vimy). The oil content on a dry weight basis increased steadily until about 20 d after flowering (DAF). The proportion of α-linolenic acid (α-18∶3, 18∶3cisΔ^{9, 12, 15}) in TAG increased during seed development in both cultivars while the proportions of linoleic acid (18∶2cisΔ^{9, 12}) and saturated FA decreased. The developmental and substrate specificity characteristics of microsomal DAG acyltransferase (DGAT, Ec 2.3.1.20) and lysophosphatidic acid acyltransferase (LPAAT, EC 2.3.1.51) were examined using cultivar AC Emerson. The maximal acyltransferase specific activities occurred in the range of 8–14 DAF, during rapid lipid accumulation on a per seed basis. Acyl-CoA of EPA (20∶5cisΔ^5,8,11,14,17) or DHA (22∶6cis ^{4,7,10,13,16,19}) were included in the specificity studies. DGAT displayed enhanced specificity for α-18∶3-CoA, whereas the preferred substrate of LPAAT was 18∶2-CoA. Both enzymes could use EPA- or DHA-CoA to varying extents. Developing flax embryos were able to take up and incorporate these nutritional FA into TAG and other intermediates in the TAG-formation pathway. This study suggests that if the appropriate acyl-CoA-dependent desaturation/elongation pathways are introduced and efficiently expressed in flax, this may lead to the conversion of α-18∶3-CoA into EPA-CoA, thereby providing an activated substrate for TAG formation.     

In vivo and in vitro lipid accumulation inBorago officinalis L.

Seeds of 13 accessions of borage (Borago officinalis) varied in total fatty acid content from 28.6 to 35.1% seed weight, with linoleic, γ-linolenic, oleic and palmitic as the predominant fatty acids, averaging 38.1%, 22.8%, 16.3% and 11.3% of total fatty acids, respectively. There was an inverse relation between γ-linolenic acid (25.0 to 17.6%) and oleic acid (14.5 to 21.3%). Fatty acid content of leaf tissues was 9.1% dry weight, with α-linolenic acid 55.2% and γ-linolenic acid 4.4% of total fatty acids. Cotyledons were the major source of fatty acids in seeds. Seed fatty acid content increased from <1 mg at six days postanthesis to about seven mg at maturity (22 to 24 days). Individual fatty acid content of seed was relatively constant after day 8. When immature embryos from 6 to 16 days postanthesis were cultured in a liquid or semisolid basal medium, fatty acid composition was similar to that of in vivo-grown seeds. Growth of cultured embryos decreased as sucrose concentration was increased from 3 to 20% in the basal medium, and most embryos did not survive 30% sucrose; fatty acid as a percentage of dry weight was maximal at 6% sucrose.     

基因工程方法增加微藻脂质积累研究进展

综述了微藻油脂合成途径的国内外研究现状,介绍了脂肪酸合成途径和Kennedy途径这两个TAG合成的关键步骤,阐述了通过基因工程方法强化脂质合成的成功经验,根据所调控的关键酶,分为增强脂肪酸合成途径、增强Kennedy途径和抑制脂肪酸合成的竞争途径三种调控策略,在此基础上,对未来微藻脂质的研究进行了展望。     

金属离子对产油微生物油脂积累影响的研究进展

利用产油微生物合成含量丰富的油脂,对于解决石化能源日益紧缺问题,改善人类生活水平具有重要意义.金属离子能影响产油微生物生长形态、细胞内外渗透压和油脂合成关键酶活力等,对产油微生物油脂合成有重要的调控作用.本文首先介绍了产油微生物的产油机制,随后重点阐述了金属离子对产油微生物油脂积累的影响及其分子机理,最后对进一步探讨金属离子在产油微生物发酵过程中的作用研究提出一些建议.文章指出由于产油微生物油脂合成途径不尽相同,在工业上利用产油微生物生产油脂时,应从该微生物油脂合成的主要途径入手,找出该途径中的关键酶,随后充分考虑不同微生物对金属离子的耐受性、不同金属离子对微生物形态和胞内关键酶活力的影响,以及不同金属离子之间对同种关键酶的活性中心是否存在竞争或协同的关系等,从而制定可行的金属离子添加控制策略.     

The lipid depressant activities of whole fish and their component oils

Hypercholesteremic rats were used to investigate the lipid depressant activities of lyophilized whole fish prepared from menhaden, silver salmon, mullet, and ocean perch. Ingestion of the whole fish supplements promoted a significant reduction in the circulating levels of cholesterol and phospholipids, and in the TC/TP ratios of blood lipids from the rat. The effects of whole fish were duplicated by feeding rats proportionate amounts of the oils found in these fish supplements. These supplements had similar, but less dramatic, effects on the liver lipids of the rats. The nonlipid components, isolated from the fish, had no apparent influence on the distribution of lipids in the blood and liver tissues. The preparations of lipid and nonlipid components of the fish are described, and the GLC analyses of marine oils are discussed. Presented, in part, at the A.O.C.S. Meeting in Chicago, 1961. Researches supported by U.S. Department of Interior, Fish & Wildlife Service, American Heart Association, U.S. Public Health service and the Hormel Foundation. These studies were completed during the tenure of an Established Investigatorship from the American Heart Association.     

二乙醇胺强化胶球藻Coccomyxa subellipsoidea C-169固定CO2和积累油脂

以优良藻株胶球藻Coccomyxa subellipsoidea C-169为受试对象,探究不同二乙醇胺（DEA）浓度对胶球藻固定CO₂及积累油脂的影响。结果表明,适宜浓度DEA可显著提高胶球藻固定CO₂和积累油脂效率。在40mg/L DEA条件下,胶球藻生物量、CO₂固定效率、油脂含量、油脂产率均达到最大值为0.97g/L、225.98mg/(L·d)、64.33%、59.9mg/(L·d),分别较无DEA对照提高了1.64倍、1.64倍、1.15倍和1.27倍。外源DEA作用提高了体系气液传质系数,增强CO₂传质效率,使得胶球藻可用无机碳源比例增加,同时上调固碳路径Rubisco和CA加强胶球藻固定CO₂,上调脂肪酸路径ACCase以及下调ACCase竞争路径PEPC为油脂合成积累提供前体和能量,从而协同强化了胶球藻固定CO₂和积累油脂。本文研究结果为工业化胶球藻CO₂生物减排及可再生能源开发提供依据。     

Changes in minor lipid components during interesterification

Fats and oils have limited applications in their natural form due to their specific chemical composition. To widen their application and functionality, they need to be modified. Interesterification is one of the modification processes used for this purpose and has advantages over hydrogenation which generates considerable amounts of undesirable trans fatty acids. Numerous studies describe changes occurring during interesterification in triacylglycerols and in physical and chemical properties of the end‐products. The few literature reports available have shown inconsistent results from a slight to extensive loss of tocopherols during the interesterification process. This paper provides information on the effects of interesterification on minor lipid components such as tocopherols, phytosterols and phytosterol oxidation products.     

Fluorescent products of phospholipids during lipid peroxidation

During peroxidation, phosphatidyl ethanolamine and phosphatidyl serine formed fluorescent chromophores with maximum emission at 435 nm and maximum excitation at 365 nm. The development of fluorescence was related to formation of thiobarbituric acid reactive substance during lipid peroxidation. This relationship was studied by reacting dipalmityl phosphatidyl ethanolamine with the oxidation products of the methyl esters of arachidonic, linolenic and linoleic fatty acids. Reaction parameters affecting the development of lipid-extractable fluorescent chromophores are: the production of peroxidation products, especially malonaldehyde, from autoxidation of polyunsaturated fatty acids; the length of time these products react; and the availability of reactive amino groups on the phospholipids.     

生化法处理一硝基甲苯生产废水

一硝基甲苯生产废水在国内均采用焚烧法处理，存在处理成本高，二次污染重等缺点。采用生化法经电偶氧化、水解酸化、接触氧化等单元处理，可达标排放。经一年多试运行，效果良好。     

Effects oftrans fatty acids on lipid accumulation in 3T3-L1 cells

Previous work had shown that dietarytrans fatty acids (tFA) resulted in decreased fat deposition in adipose tissue. This study was conducted to see iftFA 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 werecis fatty acids, whereas those in the experimental media contained bothcis andtrans 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 oftFA, due primarily to a decrease in the nonpolar lipid content of cells exposed totFA, and linoleate to arachidonate ratios were higher in cells supplemented withtFA. Calculations comparing sums of saturated and monounsaturated fatty acids in cells at the differentiating adipocyte stage suggested thattFA may have replaced monoun-saturated 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 thein vivo effects oftFA seen in previous work with mouse adipose tissue. It was concluded that the 3T3-L1in vitro model is an appropriate system for further studies oftFA and lipid metabolism in adipose tissue.     

Temperature effects on in vitro lipid accumulation in asexual embryos ofTheobroma cacao L.

Asexual embryos of cacao were grown for 40–50 days in a modified Murashige and Skoog liquid medium with sucrose concentration increased stepwise from 3 to 27% at temperatures of 10, 17, 20, 23, 26, 29, 32 or 35 C. Temperature influenced overall embryo growth as well as lipid accumulation and composition. Maximum growth occurred at 29 C, whereas maximum lipid and fatty acid accumulation occurred at 26 C. The proportion of individual fatty acids as total fatty acids accumulated per asexual embryo was constant at each temperature but varied with temperature from 10 to 35 C. The fatty acid composition of asexual embryos grown at 26 C was the most similar to that of cocoa butter, the lipid from mature zygotic embryos produced in vivo.     

Dietary diacylglycerol prevents high-fat diet-induced lipid accumulation in rat liver and abdominal adipose tissue

The inhibitory effects of 1,3-diacylglycerol (DAG) on diet-induced lipid accumulation in liver and abdominal adipose tissue of rats were investigated in the present study. Male Sprague-Dawley rats were given free access to diets containing 7 wt% TAG (low TAG), 20 wt% TAG (high TAG), or 20 wt% DAG (high DAG), respectively, for 8 wk. The body weight of rats in the 20% high-TAG group increased significantly, and the weights of their abdominal adipose tissue and liver also showed a significant increase compared with rats in the low-TAG group. However, the high-DAG diet resulted in both a significant reduction in body weight gain (with a decrease of 70.5%) and an increase in the ratio of abdominal fat to body weight (by 127%) compared with the high-TAG diet. As well, the liver TAG and serum TAG levels of the high-DAG group were significantly lower than those of the high-IAG group. These effects were associated with up-regulation of acyl-CoA carnitine acyltransferase (ACAT) and down-regulation of acyl-CoA DAG acyltransferase (DGAT) in the liver. However, no significant difference was observed in the activities of alanine aminotransferase and aspartate aminotransferase among the groups (P>0.05). The present results indicate that dietary DAG reduced fat accumulation in viscera and body, and these effects may be involved with up-regulation of ACAT and down-regulation of DGAT in the liver.     

Nitrate accumulation and greenhouse gas emissions during compost storage

Greenhouse gases (CO₂, CH₄ and N₂O) are emitted during livestock manure handling, including composting, storage and land application. However, published data on emission rates of these gases during storage are sparse. In this study, the levels of GHG emissions and N levels during compost storage were investigated. The compost materials were produced by composting livestock manure for 133 d with 0, 10, 20 and 30% phosphogypsum (PG) or 10, 20 and 30% sand amendment. These compost materials were then stored on a clay pad for 233 d. Results from this study indicated that TN content did not change but mineral N content increased significantly during the 233 d storage for all treatments. The higher mineral N content in compost increases its agronomic value. There were only trace amounts of CH₄ and N₂O emissions. The C loss during storage was mainly as CO₂ and accounted for about 2.9 to 10% of total C initially in the compost. This information is vital to livestock manure life cycle analysis, and can be used to develop best manure management strategies that reduce GHG emissions from livestock production. The LRC Contribution No. 387-06006.     

Mathematical evaluation of intermediates accumulation during microbial phenanthrene degradation

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in the soil environment, and considered to be hazardous due to their toxic and carcinogenic properties. Intermediates accumulation during PAHs degradation significantly alters the overall biodegradation rate and toxicity of the soil environment. The biodegradation pathway of phenanthrene, a 3-ring PAH, consisting of 14 enzymatic steps was analyzed to determine the release pattern of the intermediates by mathematical calculation of permeability using a membrane transport model. The intermediates with high permeability such as 1-hydroxy-2-naphthoic acid were consistent with the compounds frequently observed in laboratory or field in the literature.     

Metabolome analysis reveals ethanolamine as potential marker for improving lipid accumulation of model photosynthetic organisms

BACKGROUND: Many researchers focus on exploring approaches to improve lipid productivity by photosynthetic organisms. Metabolomic analysis provides a new way to globally explore metabolic changes. To elevate lipid yields in the process of biodiesel production using photosynthetic organisms as feedstock, metabolomics combined with orthogonal partial least‐squares discriminant analysis (OPLS‐DA) is being applied widely to seek potential markers in regulation of lipid production. Herein, metabolic differences among three photosynthetic organisms Scenedesmus obliquus, Synechocystis sp. PCC6803 and Anabaena sp. PCC7120 were analyzed by gas chromatography coupled with time‐of‐flight mass spectrometry (GC‐TOF‐MS). RESULTS: In total, 74 metabolites were identified by GC‐TOF‐MS. The OPLS‐DA model revealed good correlation between metabolites and lipid content (R² = 0.9916). Nine compounds including ethanolamine were selected as potential markers affecting lipid accumulation. Herein, the highest level of C18:3 revealed its roles in regulation of the unsaturated degree of fatty acids. Further study revealed that exogenous ethanolamine (2 mmol L^?1) significantly increased the lipid content (22%) in Scenedesmus obliquus. In particular, ethanolamine significantly elevated the levels of C16:2, C18:1, and C18:2. CONCLUSION: Metabolomic analysis is a useful tool to search for potential markers to improve lipid accumulation of photosynthetic organisms. Ethanolamine can be regarded as an alternative compound to improve lipid content and fatty acid levels for biodiesel production. Copyright © 2012 Society of Chemical Industry     

植物激素诱导对小球藻Chlorella vulgaris细胞生物量和油脂合成积累的影响

目的探讨植物激素诱导对小球藻Chlorella vulgaris细胞生物量、油脂含量及内生激素浓度的影响规律。方法分别以天然植物源脱落酸(abscisic acid,ABA)、工业合成萘乙酸(1-naphthylacetic acid,NAA)和二氯苯氧基乙酸(2,4-dichlorophenoxyacetic acid,2,4-D)诱导培养小球藻Chlorella vulgaris细胞,细胞干重法检测藻细胞生物量及油脂含量,气相色谱-质谱(GC-MS)分析脂肪酸组成,高效液相色谱-质谱(HPLC-MS)测定内生激素浓度。结果 NAA诱导对藻细胞生长和脂质合成积累表现出显著的促进效应,其最大油脂产率为418.6 mg/(L·d),分别为2,4-D和ABA诱导藻细胞的1.48和1.83倍;NAA诱导有效调整了小球藻胞内饱和脂肪酸和单不饱和脂肪酸比例,使其组成和含量更易于制备高质量生物柴油;NAA作为激素合成前体参与内生激素(吲哚乙酸、茉莉酸和水杨酸)生物合成,促进内生激素水平升高,而提高浓度的内生激素可能通过一定的信号途径刺激藻细胞生长和合成脂质。结论植物类激素NAA可作为植物源激素替代物用于低成本微藻油脂生产,为制备经济可行的、高质量生物柴油提供了新的途径。     

Effect of acetic acid on lipid accumulation by glucose‐fed activated sludge cultures

BACKGROUND: The effect of acetic acid, a lignocellulose hydrolysis by‐product, on lipid accumulation by activated sludge cultures grown on glucose was investigated. This was done to assess the possible application of lignocellulose as low‐cost and renewable fermentation substrates for biofuel feedstock production. RESULTS: Biomass yield was reduced by around 54% at a 2 g L^?1 acetic acid dosage but was increased by around 18% at 10 g L^?1 acetic acid dosage relative to the control run. The final gravimetric lipid contents at 2 and 10 g L^?1 acetic acid levels were 12.5 ± 0.7% and 8.8 ± 3.2% w/w, respectively, which were lower than the control (17.8 ± 2.8% w/w). However, biodiesel yields from activated sludge grown with acetic acid (5.6 ± 0.6% w/w for 2 g L^?1 acetic acid and 4.2 ± 3.0% w/w for 10 g L^?1 acetic acid) were higher than in raw activated sludge (1–2% w/w). The fatty acid profiles of the accumulated lipids were similar with conventional plant oil biodiesel feedstocks. CONCLUSIONS: Acetic acid enhanced biomass production by activated sludge at high levels but reduced lipid production. Further studies are needed to enhance acetic acid utilization by activated sludge microorganisms for lipid biosynthesis. Copyright © 2011 Society of Chemical Industry     

Iron accumulation in oil during the deep-fat frying of meat

Iron accumulation in oil is a potential problem when frying food containing substantial amounts of iron. Selected meat products (skinless chicken breast, beef liver, and lean beef) were ground and fried (ca. 2-cm spheres, ca. 10 g/sphere) in partially hydrogenated soybean oil (PHSBO). Samples (450 g) of ground meat were fried 3 times/h for 8 h/d for 3 d. Oil samples were collected for analysis for iron (every 8 h) and oil degradation (every 4 h) and replaced with fresh oil. The iron contents of oil samples after 3 d of frying were approximately 0.11, 0.48, and 4.01 mg of iron/kg of PHSBO for the oil used to fry chicken, beef, and liver, respectively. There was a notable darkening in color and an increased tendency to foam for the beef liver oil sample compared with the other samples. After frying, the acid values were 0.9, 1.1, and 1.4 for the oil samples for chicken, beef, and liver, respectively. After frying, the p-anisidine values were 11.5, 12.8, and 32.6 for the oil samples for chicken, beef, and liver, respectively; the food oil sensor values were 0.96, 0.96, and 0.83 for the oil samples for chicken, beef, and liver, respectively.     

Damage accumulation mechanisms during dynamic compressive failure of boron carbide

This paper explores the compressive response of two grades of boron carbide across a range of strain rates between 10² to 10³ s^?1. Using ultra-high-speed photography to perform digital image correlation in conjunction with strain gauges, the evolution of apparent elastic moduli was tracked through the failure process. Analysis of damage metrics shows that the two most important measures of damage accumulation in these materials are apparent changes to shear modulus and Poisson’s ratio, rather than only apparent changes to Young’s modulus as is commonly assumed in the literature. For one grade of the boron carbide the range of strain-rates studied also included a transition from quasi-static-type failure behavior where bulking was not a significant factor, to dynamic-type failure where bulking became a significant influence on failure; this transition was linked to material-specific fracture mechanisms. For the other grade of boron carbide, only dynamic-type failure was seen in this strain-rate range, suggesting that the transition point was at a lower strain-rate.     

Antioxidant activities of tocopherols on Fe2+-ascorbate-induced lipid peroxidation in lecithin liposomes

The antioxidant activities of 4 tocopherols, tocol, and a water-soluble model analog of α-tocopherol were compared. Egg lecithin liposomes were used and oxidation was catalyzed by Fe²⁺-ascorbate. The activities decreased in the order α->β->γ->δ-tocopherol>tocol, in agreement with their potencies in vivo. The water-soluble analog was the least effective. Activity depended on the molar ratio of antioxidant to unsaturated lipid, with one molecule each of the α-, β-, γ-, δ-tocopherol and tocol capable of protecting, respectively, 220, 120, 100, 30 and 20 molecules of polyunsaturated fatty acid. The mechanism of possible antioxidant effect of the compounds used is discussed.