Kinetic profile of the cellular lipid composition in an oleaginous Yarrowia lipolytica capable of producing a cocoa-butter substitute from industrial fats

Cell growth, lipid accumulation and cellular lipid composition of Yarrowia lipolytica growing on mixtures of industrial fats containing stearic, oleic, linoleic and palmitic acid have been studied. During growth, the strain incorporated oleic and linoleic acids more rapidly than the saturated fatty acids. Relatively high lipid accumulation (up to 0.44 g of lipids per g of dry matter) was observed when stearic acid was included in the culture medium. In contrast, substrates rich in oleic acid did not favor cellular lipid accumulation. The accumulated lipids, mainly composed of triacylglycerols (45-55% w/w), demonstrated a different total fatty acid composition compared with that of the substrate; in all cases, the microorganism showed the unusual capacity to increase its cellular stearic acid level, even if this fatty acid was not found in high concentrations in the substrate. This permitted the synthesis of interesting lipid profiles with high percentages of stearic acid and non-negligible percentages of palmitic and oleic acid, with a composition resembling that of cocoa-butter.     

Modification of cellular fatty acid composition of Hep-G2 cells: effect of antioxidants on cholesterol esterification and secretion

Modification of fatty acid composition of Hep-G2 cells was achieved by 7-9 days of supplementation of culture medium with palmitic, oleic or linoleic acid. Cholesterol release into serum-free culture medium during 24 h of incubation was significantly lower in cells supplemented with linoleic acid, when compared to those supplemented with palmitic, oleic or no additional fatty acid. In cells cultured in the presence of linoleic acid, less [3H]cholesterol was esterified to cholesteryl ester and the mass of cholesteryl ester was significantly lower than in cells cultured with palmitic acid or with no additional fatty acid. The reduction in [3H]cholesterol secretion and the impairment in cholesterol esterification in linoleic acid-treated cells was prevented by addition of butylated hydroxytoluene or probucol concurrently with the fatty acid. The antioxidants also increased esterification and [3H]cholesterol release in cells supplemented with the other fatty acids. It is suggested that cholesterol secretion and esterification are sensitive to peroxidation.     

Stereospecific distribution of plamitic acid in the triacylglycerols of rat adipocytes. Effects of varying the composition of the substrate fatty acid in vitro

The effects of inclusion of different fatty acids in the medium on the rate of esterification of palmitic acid and its stereospecific distribution among the three positions of the triacyl-sn-glycerols by preparations of rat adipocytes in vitro have been determined. Myristic acid, stearic acid, oleic acid and linoleic acid were used as diluents and the concentration of the combined unesterified fatty acids in the medium was held constant; only the proportion of palmitic acid was varied. The amount of palmitic acid esterified was always linearly related to its relative concentration in the medium and was not significantly affected by the nature of the diluent fatty acid chosen. Constant relative proportions were recovered in triacylglycerols and in intermediates in each instance. The amount of palmitic acid esterified to each of the positions of the triacyl-sn-glycerols was linearly dependent on the relative proportion in the medium but the nature of the relationship was markedly influenced by which fatty acid was present. When stearic acid was present, simple relationships were found over the whole range tested. When either myristic acid, oleic acid or linoleic acid was present, abrupt changes in the manner of esterification of palmitic acid were observed in position sn-1 when the relative concentrations of palmitic acid and the diluent reached critical values, which differed with each fatty acid. In position sn-2 when oleic acid or linoleic acid was present, a similar change was observed, and in position sn-3 it was obtained with myristic acid as diluent. The results are discussed in terms of changes in the relative affinities of the acyltransferases for palmitic acid. Palmitic acid was esterified into various molecular species in proportions that indicated acylation with non-correlative specificity at higher relative concentrations but not at lower.     

Influence of the diet on the portal and lymph transport of decanoic acid in rats. Simultaneous study of its mucosal catabolism

The absorption route of decanoic acid, a medium chain fatty acid, infused in the intestinal lumen in the presence and absence of long chain fatty acids, has been analyzed. Ex vivo perfusion of isolated intestinal loop and intestinal lymph fistula was the technique used. Decanoic acid infused alone was essentially transported through the portal system. If infused in association with monopalmitin, oleic or palmitic acid, up to 3% of decanoic acid could be diluted in the lymph. Moreover, decanoic acid oxidation by the mucosa increased significantly with palmitic acid and in contrast decreased with oleic acid. These data show that both intestinal absorption processes and mucosal oxidation of the medium chain fatty acids are modulated by the lipid components of the diet.     

Regulation of Lipid Droplet Size in Mammary Epithelial Cells by Remodeling of Membrane Lipid Composition—A Potential Mechanism

Milk fat globule size is determined by the size of its precursors—intracellular lipid droplets—and is tightly associated with its composition. We examined the relationship between phospholipid composition of mammary epithelial cells and the size of both intracellular and secreted milk fat globules. Primary culture of mammary epithelial cells was cultured in medium without free fatty acids (control) or with 0.1 mM free capric, palmitic or oleic acid for 24 h. The amount and composition of the cellular lipids and the size of the lipid droplets were determined in the cells and medium. Mitochondrial quantity and expression levels of genes associated with mitochondrial biogenesis and polar lipid composition were determined. Cells cultured with oleic and palmitic acids contained similar quantities of triglycerides, 3.1- and 3.8-fold higher than in controls, respectively (P < 0.0001). When cultured with oleic acid, 22% of the cells contained large lipid droplets (>3 μm) and phosphatidylethanolamine concentration was higher by 23 and 63% compared with that in the control and palmitic acid treatments, respectively (P < 0.0001). In the presence of palmitic acid, only 4% of the cells contained large lipid droplets and the membrane phosphatidylcholine concentration was 22% and 16% higher than that in the control and oleic acid treatments, respectively (P < 0.0001). In the oleic acid treatment, approximately 40% of the lipid droplets were larger than 5 μm whereas in that of the palmitic acid treatment, only 16% of the droplets were in this size range. Triglyceride secretion in the oleic acid treatment was 2- and 12-fold higher compared with that in the palmitic acid and control treatments, respectively. Results imply that membrane composition of bovine mammary epithelial cells plays a role in controlling intracellular and secreted lipid droplets size, and that this process is not associated with cellular triglyceride content.     

Selective fatty acid release from intracellular phospholipids caused by PCBs in rat renal tubular cell cultures

The purpose of this study was to explore the influence of different polychlorinated biphenyls (PCBs) upon the release of oleic and palmitic acid from the intracellular lipids, which were previously labeled with [3H]oleic or [3H]palmitic acid, respectively. Studies have been realized with Aroclor 1248 (a commercial PCB mixture with 48% chlorine by weight), and two pure PCB congeners: 3,3',4, 4'-tetrachlorobiphenyl (a non-ortho-substituted planar congener) and 2,2',4,4',5,5'-hexachlorobiphenyl (a di-ortho-substituted nonplanar congener). The treatment of cells with Aroclor 1248 increased [3H]oleic acid release in a concentration-dependent manner. Our results showed that only the di-ortho-substituted congener which prefers a nonplanar configuration stimulated the release of [3H]oleic acid from the intracellular phospholipids to the culture medium, while the exposure of cell cultures to the chosen non-ortho-substituted coplanar congener did not alter the release of [3H]oleic acid to the culture medium. Finally, none of the PCBs studied could increase the release of [3H]palmitic acid from the intracellular stores significantly. The possibility that these differential alterations in the fatty acid release affect cell function during PCB exposure should therefore be postulated.     

Replacement of the aliphatic chains of Clostridium acetobutylicum by exogenous fatty acids: regulation of phospholipid and glycolipid composition.

The membrane lipid aliphatic chains of Clostridium acetobutylicum ATCC 4259 have been extensively modified by growth in biotin-free medium containing vitamin-free casein hydrolysate supplemented with either elaidic acid, oleic acid, or mixtures of palmitic and oleic acids. Growth with elaidic acid resulted in polar lipids containing 88.6% 18:1 acyl chains and 94.5% 18:1 ether-linked chains. Growth with oleic acid resulted in comparable levels of enrichment of the lipids with 18:1 chains and C19 chains containing cyclopropane rings. When cells were grown with mixtures of palmitic and oleic acids, the ether-linked chains of the plasmalogens were greater than or equal to 64% 18:1 plus C19 chains containing cyclopropane rings at all ratios of oleic to palmitic acid in the medium. The acyl chains reflected the palmitic acid content of the medium more closely. Marked changes were observed in both phospholipid and glycosyldiglyceride compositions as the lipid acyl and ether-linked chains became more enriched with unsaturated and cyclopropane chains. The ratio of the glycerol acetal of plasmenylethanolamine to phosphatidylethanolamine increased, the ratio of cardiolipin to phosphatidylglycerol decreased, and the ratio of diglycosyldiglyceride to monoglycosyldiglyceride increased. However, the monoglycosyldiglyceride/diglycosyldiglyceride ratio was lower for cells grown on 100% oleic acid than for cells grown on 60 or 80% oleic acid. In the membranes of cells grown on 100% oleic acid, the ratio of glycolipids to phospholipids was lower than that found in cells grown on 60% oleic acid. These results indicate that C. acetobutylicum regulates its polar lipid composition in a complex manner involving phospholipids and glycosyldiglycerides. These changes can affect the equilibria between those lipids that form bilayers and those lipids that tend to form nonlamellar phases when enriched with unsaturated aliphatic chains. Phosphoglycolipids of unknown structure were also observed in cells grown either with biotin or with fatty acids. The content of the most abundant phosphoglycolipid also varied with the degree of unsaturation of the cellular lipids.     

Myristic acid, unlike palmitic acid, is rapidly metabolized in cultured rat hepatocytes

This study was designed to examine and compare the metabolism of myristic and palmitic acids in cultured rat hepatocytes. [1-(14)C]-Labeled fatty acids were solubilized with albumin at 0.1 mmol/L in culture medium. Incubation with 24-hr cultured hepatocytes was carried out for 12 hr. Myristic acid was more rapidly (P < 0.05) taken up by the cells than was palmitic acid (86.9 +/- 0.9% and 68.3 +/- 5.7%, respectively, of the initial radioactivity was cleared from the medium after 4 hr incubation). Incorporation into cellular lipids, however, was similar after the same time (33.4 +/- 2.8% and 34.9 +/- 9.3%, respectively, of initial radioactivity). In the early phase of the incubation (30 min), myristic acid was more rapidly incorporated into cellular triglycerides than was palmitic acid (7.4 +/- 0.9% and 3.6 +/- 1.9%, respectively, of initial radioactivity). However, after 12 hr incubation, the radioactivity of cellular triglycerides, cellular phospholipids, and secreted triglycerides was significantly higher with palmitic acid as precursor. Myristic acid oxidation was significantly higher than that of palmitic acid (14.9 +/- 2.2% and 2.3 +/- 0.6%, respectively, of the initial radioactivity was incorporated into the beta-oxidation products after 4 hr). Myristic acid was also more strongly elongated to radiolabeled palmitic acid (12.2 +/- 0.8% of initial radioactivity after 12 hr) than palmitic acid was to stearic acid (5.1 +/- 1.3% of initial radioactivity after 12 hr). The combination of elongation and beta-oxidation results in the rapid disappearance of C14:0 in hepatocytes whereas C16:0 is esterified to form glycerolipids. This study provides evidence that myristic acid is more rapidly metabolized in cultured hepatocytes than is palmitic acid.     

Lipid particle composition of the yeast Yarrowia lipolytica depends on the carbon source

Lipid particles (LP) of all types of cells are a depot of neutral lipids. The present investigation deals with the isolation of LP from the yeast Yarrowia lipolytica and the characterization of their lipid and protein composition. Properties of LP varied depending on the carbon source. LP from glucose-grown cells revealed a mean diameter of 650 nm with a hydrophobic core mainly formed of triacylglycerols (TAG) and a minor amount of steryl esters (SE). Oleic acid was the major fatty acid species esterified in LP. When cells were grown on oleic acid, LP size increased 3.8-fold, the particles exhibited a significantly lower ratio of TAG to SE, and the relative amount of oleic acid in LP lipids increased compared to cells grown on glucose. Analysis of LP proteins revealed an increasing number of polypeptides when cells were shifted from glucose- to oleic acid-containing medium. Twenty-one major LP proteins were identified under both growth conditions, and additional nine polypeptides were specific for growth on oleic acid. Identification of these proteins by MS and comparison of the deduced ORFs to those from Saccharomyces cerevisiae revealed that most proteins of Y. lipolytica LP are involved in lipid metabolism. LP proteins specific for growth on oleic acid are also enzymes involved in lipid metabolism, but some of them are also components of the intracellular traffic machinery. Thus, proteom analysis of LP proteins suggests involvement of this compartment in different cell biological processes.     

The lipid composition and permeability to the triazole antifungal antibiotic ICI 153066 of serum-grown mycelial cultures of Candida albicans

The total lipid content of Candida albicans (serotype A: NCPF 3153) exponential-phase mycelial cultures grown in tissue-culture medium 199 (containing 10%, v/v, foetal calf serum) was 29.8 +/- 8 mg (g dry weight)-1 (mean +/- SD). The weight ratios of phospholipid to neutral lipid and phospholipid to non-esterified sterol were 2.6 +/- 0.4 and 24.9 +/- 0.5, respectively. The major phospholipid was phosphatidylcholine with smaller amounts of phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and diphosphatidylglycerol; the most abundant fatty acids were palmitic, palmitoleic, oleic and linoleic acids. The major neutral lipids comprised esterified sterol, triacylglycerol and non-esterified fatty acid with a smaller amount of non-esterified sterol. The fatty acid compositions of the three fatty-acid-containing neutral lipids were distinct from each other and the phospholipids. Comparison with previous data on yeast cultures of C. albicans A grown in glucose broth shows that mycelial cultures have a larger lipid content, lower phospholipid to neutral lipid ratio and higher phospholipid to non-esterified sterol ratio. We now show that mycelial cultures were more permeable to a [14C]triazole antifungal antibiotic compared with exponentially growing yeast cultures of several azole-sensitive strains. Taken together these data are consistent with there being a relationship between the phospholipid/non-esterified sterol ratio of a culture and its ability to accumulate a triazole.     

Isolation and characterization of a novel monoacylated glucopyranosyl neutral lipid from the plasma membrane of Acholeplasma laidlawii B

The level of a normally minor component of the membrane polar lipids of Acholeplasma laidlawii B was significantly increased when the glucose supplement in the growth medium was reduced. Under such glucose-limiting conditions the proportion of this component was found to be dependent upon the fatty acid supplement and could approach 55-60% of the total polar lipids when palmitic acid was used to supplement the growth medium. A number of physical measurements, along with specific chemical and enzymic degradation studies followed by a careful analysis of the degradation products, enabled us to tentatively identify this lipid as a polyprenyl-alpha-D-glucoside with a long-chain fatty acid esterified to the 2-hydroxyl group of the sugar moiety. This lipid exhibited some unusual thermotropic phase properties and our observations suggest that it may not be easily miscible with the other membrane lipid components. The structure and physical properties of this unusual glycolipid also suggest that it may be capable of forming non-bilayer phases under physiologically relevant conditions.     

Lipid and sterol composition of the pollen of the west african oilpalm, Elaeis guineensis

The lipid classes, fatty acid methyl esters and the sterols of oilpalm pollen were analysed. The neutral lipid fraction consisted of triglycerides, esterified and free sterols and trace amounts of hydrocarbons. Monogalactosyl and digalactosyl diglycerides, phosphatidyl choline, phosphatidyl inositol and phosphatidyl ethanolamine represented the polar lipids. The major fatty acids were linoleic, palmitic and linolenic acids together with small to trace amounts of oleic, stearic, arachidic, myristic, lauric, palmitoleic and margaric acids. Unsaturated fatty acids predominated over saturated ones in the ratio of 3:2. The 4-desmethyl sterols were the major phytosterols in the free form but they constituted a lower proportion of the sterols in the esterified state. 28-Isofucosterol was isolated and characterized as the principal sterol.     

Lipid interactions with in vitro development of mammalian zygotes

Rabbit zygotes were tested for their ability to sequester radiolabeled acetate, oleate, and arachidonate in intracellular lipid. Radiolabeled arachidonic acid was concentrated 170 ± 28-fold (mean ± SEM) and oleic acid was concentrated 105 ± 26-fold in zygotic lipids during 6 hr of culture when compared with the initial concentrations in culture medium. Acetate was not concentrated into lipids by cultured zygotes. Both long chain fatty acids were incorporated mainly as triglyceride. Polydimethylsiloxane fluid, used to cover the microdroplets of medium during culture, demonstrated lipophilic properties. This characteristic was utilized to indirectly transfer lipids to culture medium, permitting examination only of lipoidal properties of test extracts on embryonal development. For rabbit zygotes, blood plasma extract was detrimental and whole blood extract was beneficial for embryonal cleavage rates during the first 24 hr of culture. A higher proportion of mouse zygotes developed to blastocysts when cultured in modified Ham's F-10 medium compared to BMOC medium, and this difference was negated by inclusion of a lipid extract prepared from rabbit oviductal fluid in the culture system. Comparison of fatty acid analyses of the lipid extracts with development rates of zygotes suggests that modified rates of embryo development may be associated with ratios of individual fatty acids presented to the culture medium rather than with the presence of any single fatty acid.     

Modification of CaCo-2 cell membrane fatty acid composition by eicosapentaenoic acid and palmitic acid: effect on cholesterol metabolism

Membrane fatty acid composition of CaCo-2 cells was modified by incubating the cells for 8 days in medium containing 100 microM eicosapentaenoic acid or palmitic acid. The effect of membrane fatty acid changes on cholesterol metabolism was then studied. Cells incubated with eicosapentaenoic acid had significant changes in membrane fatty acid composition with an accumulation of 20:5 and 22:5 and a reduction in monoenoic fatty acids compared to cells grown in palmitic acid. Intracellular cholesteryl esters could not be detected in CaCo-2 cells grown in the presence of the n-3 polyunsaturated fatty acid. In contrast, cells incubated with the saturated fatty acid contained 2 micrograms/mg protein of cholesteryl esters. Cells grown in eicosapentaenoic acid, however, accumulated significantly more triglycerides compared to cells modified with palmitic acid. The rate of oleic acid incorporation into triglycerides was significantly increased in cells incubated with eicosapentaenoic acid. CaCo-2 cells modified by eicosapentaenoic acid had lower rates of HMG-CoA reductase and ACAT activities compared to cells modified with palmitic acid. The incorporation of the two fatty acids into cellular lipids also differed. Palmitic acid was predominantly incorporated into cellular triglycerides, whereas eicosapentaenoic acid was preferentially incorporated into phospholipids with 60% of it in the phosphatidylethanolamine fraction. The data indicate that membrane fatty acid composition is significantly altered by growing CaCo-2 cells in eicosapentaenoic acid. These modifications in membrane fatty acid saturation are accompanied by a decrease in the rates of cholesterol synthesis and cholesterol esterification.     

Low-temperature-induced changes in intracellular fatty acid fluxes in Dunaliella salina

Two-minute exposures to exogenous [14C]palmitic, [14C]oleic, or [14C]lauric acid differentially labeled the lipids of Dunaliella salina microsomes and chloroplasts. Changes in fatty acid desaturation and intracellular movement during a subsequent 16-h incubation in nonradioactive medium indicated a slow transfer of lipids into the chloroplast from other organelles. Since Dunaliella lacks the massive traffic of microsomally produced glycerolipids into chloroplast galactolipids that dominates chloroplast-microsome lipid relations in most plant cells, it affords a sensitive system for studying more subtle intracellular lipid fluxes. Lowering the culture temperature from 30 to 12 degrees C was more inhibitory toward glycerolipid biosynthesis in chloroplasts than in microsomes. The ability of Dunaliella chloroplasts to utilize microsomal lipids may be essential for their systematic acclimation to low temperature.     

Effect of cholesterol enrichment on 12-hydroxyeicosatetraenoic acid metabolism by mouse peritoneal macrophages

The metabolism of 12-hydroxyeicosatetraenoic acid (12-HETE) was investigated in mouse peritoneal macrophages enriched in cholesterol by incubation with acetylated low density lipoproteins. After incubating with labeled arachidonic acid, cholesterol-rich cells released more 12-HETE into the medium than unmodified macrophages. With time, however, 12-HETE decreased in the medium of both cell preparations suggesting re-uptake of this monohydroxyfatty acid and perhaps further metabolism. When control macrophages were incubated with radiolabeled 12-HETE for 2 hr, almost 70% of the cell-associated 12-HETE label was incorporated into phospholipids. In contrast, in cholesterol-rich cells, only 31% of the 12-HETE label was incorporated into phospholipids. Bee venom phospholipase completely hydrolyzed the label, suggesting that the monohydroxyfatty acid was esterified at the sn-2 position of the phospholipid. In cholesterol-rich cells, 69% of the 12-HETE was diverted into neutral lipids. Two major neutral lipids were identified in cholesterol-rich macrophages. One neutral lipid band which migrated with an Rf value of 0.34 contained the hydroxylated fatty acid esterified to a glyceride. The other neutral lipid band having an Rf value of 0.49 contained cholesterol and by further analysis was found to contain predominantly cholesteryl-12-HETE. The labeled fatty acids in these two neutral lipids were mostly oxidized products of 12-HETE in contrast to the native 12-HETE observed in the phospholipids. Cholesterol-rich macrophages released 25% more products of 12-HETE metabolism than control macrophages. Two major products were observed in the medium which eluted in the area of a standard di-HETE, LTB4, on high performance liquid chromatography (HPLC) analysis. We propose that the reincorporation of 12-HETE into these neutral lipids and the increased capacity for further metabolism of this biologically potent hydroxyfatty acid could be a mechanism by which the cholesterol-rich macrophage maintains its membrane function, and regulates the amount of 12-HETE in the pericellular space.     

Deuterium nuclear magnetic resonance studies on the plasmalogens and the glycerol acetals of plasmalogens of Clostridium butyricum and Clostridium beijerinckii

Deuterium nuclear magnetic resonance was used to investigate the structure of different lipid fractions isolated from the anaerobic bacteria Clostridium butyricum and Clostridium beijerinckii. The fractions isolated from C. butyricum were (1) phosphatidylethanolamine/plasmenylethanolamine and (2) the glycerol acetal of plasmenylethanolamine, and from C. beijerinckii similar fractions containing principally (1) phosphatidyl-N-monomethylethanolamine, along with its plasmalogen, and (2) the glycerol acetal of this plasmalogen were isolated. The third fraction from both species consisted largely of the acidic lipids phosphatidylglycerol and cardiolipin along with plasmalogen forms of these lipids. Palmitic acid with deuterium labels at C-2, C-3, or C-4 or oleic acid with deuterium labels at C-2 and C-9,10 was added to the growth medium and incorporated to various extents in the lipid fractions. Biochemical analysis showed that palmitic acid and oleic acid were preferentially bound to the sn-2 and sn-1 positions, respectively, of the glycerol backbone when both fatty acids were added to the medium. From the 2H NMR spectra, the hydrocarbon chain ordering near the lipid-water interface could be determined and appeared to be similar for all three lipid fractions. The deuterium quadrupole splitting and order parameter were low at the C-2 segment and increased by almost a factor of 2 at positions C-3 and C-4 for cells fed with deuterated palmitic acid along with unlabeled oleic acid. These results agree with previous findings on pure diacyl lipids in which the sn-2 chain was found to adopt a bent conformation at the carbon segment C-2. However, two unusual quadrupole splittings could be detected for the plasmalogens.(ABSTRACT TRUNCATED AT 250 WORDS)     

The lipid composition of Acer pseudoplatanus cells grown in culture

Cells of Acer pseudoplatanus were grown in batch suspension culture for 22 days. The cultures were initiated at high cell density of 2 × 10⁵ cells per ml of culture. Growth was characterised by a short lag phase, an exponential phase of rapid cell division and growth, and finally a stationary phase. Quantitative but not qualitative changes were observed in total lipid content, fatty acids and phospholipids at different stages of growth. Total lipids, phospholipids and fatty acids showed maximum concentrations in 12 day old cells. The major phospholipids isolated were phosphatidylcholine and phosphatidylethanolamine with minor amounts of phosphatidic acid and lysophosphatides. Other lipid components present were mono- and digalactosyl diglycerides, cerebrosides, sterol glucosides, free fatty acids and esterified sterol glucosides. The major constituent fatty acids were myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2) and linolenic acid (18:3). During exponential cell growth the proportion of 16:0, 18:2 and 18:3 constituted nearly 90% of the total fatty acids. Triglycerides were the major repository of myristic acid (14:0) with substantial amounts of palmitic acid (16:0), whereas phospholipids contained 16:0, 18:2 and 18:3 in high amounts.     

响应面法优化木薯淀粉发酵生产单细胞油脂工艺

采用响应面分析法对发酵性丝孢酵母菌株以木薯淀粉水解液为原料合成微生物油脂的培养条件进行优化。首先利用Plackett-Burman试验设计确定影响油脂产量的主要因素,在此基础上再利用Box-Behnken试验设计及响应面分析法对其进行条件优化。结果表明,发酵温度、C/N、pH对油脂产量具有显著影响,产油脂的最佳发酵条件为:发酵温度28.78°C、C/N 126.18、pH 6.69,油脂产量达到14.88g/L,比优化前提高了28.6%。同时,气相色谱分析表明,微生物油脂脂肪酸组成成分主要包括棕榈酸、硬脂酸、油酸、亚油酸酯等,是优良的生物柴油制备原料。     

Macrophages transfer [14C]-labelled fatty acids to pancreatic islets in culture

Macrophages are able to produce, export, and transfer fatty acids to lymphocytes in culture. The purpose of this study was to examine if labelled fatty acids could be transferred from macrophages to pancreatic islets in co-culture. We found that after 3 h of co-culture the transfer of fatty acids to pancreatic islets was: arachidonic > oleic > linoleic = palmitic. Substantial amounts of the transferred fatty acids were found in the phospholipid fraction; 87.6% for arachidonic, 59.9% for oleic, 53.1% for palmitic, and 36.9% for linoleic acids. The remaining radioactivity was distributed among the other lipid fractions analysed (namely polar lipids, cholesterol, fatty acids, triacylglycerol and cholesterol ester), varying with the fatty acid used. For linoleic acid, a significant proportion (63.1%) was almost equally distributed in these lipid fractions. Also, it was observed that transfer of fatty acids from macrophages to pancreatic islets is time-dependent up to 24 h, being constant and linear with time for palmitic acid and remaining constant after 12 h for oleic acid. These results lead us to postulate that in addition to the serum, circulating monocytes may also be a source of fatty acids to pancreatic islets, mainly arachidonic acid.