Fatty acid-containing lipids of the yeast Saccharomyces cerevisiae during post-fermentation decline in viability

On exhaustion of the sugar supply in the medium, cells of the yeast Saccharomyces cerevisiae maintained at 30°C lost most of their phospholipid content and their viability, as assessed by methylene blue staining, within a few days. Both processes occurred more rapidly in cells which had fermented glucose rather than maltose. During this period of decline the cell content of other fatty acid esters, mainly t riacylglycerols, increased. This seemed greater in cells grown with maltose than with glucose but the latter cells also synthesised distinct amounts of waxes. The total quantity of lipid per cell did not change significantly during loss of viability although the composition of the lipid fraction did.     

Lipid levels in cabbage leaves (Brassica oleracea)

Cabbage (Brassica oleracea L, var Glory) is one of the cruciferous vegetables. The objective of this study was to investigate the neutral, glyco- and phospholipids of cabbage and their fatty acid composition. Lipids from its leaves were extracted and fractionated into neutral lipids, glycolipids and phospholipids. The fatty acids of each fraction were analysed by gas liquid chromatography.     

Microwave Roasting Effects on Acyl Lipids in Soybeans (Glycine max. L.) at Different Moisture Contents

The effects of microwave roasting on acyl-lipids of soybeans were studied iti relation to moisture. During microwave treatments, triacylglycerols were hydrolyzed randomly, due to differences of moisture contents, but remained > 72% of total lipids after 20 min roasting. Phospholipids containing amino group decreased substantially (P < 0.05) in low moisture soybeans. Formation of browning substances was inhibited by increasing moisture contents. Differences (P < 0.05) in fatty acid distributions occuired (with few exceptions) when soybeans were microwaved for 12 min or more. Microwave treatments for soybeans should depend on moisture contents.     

Incorporation of unsaturated fatty acids by Saccharomyces cerevisiae: conservation of fatty-acyl saturation in phosphatidylinositol

Saccharomyces cerevisiae was grown anaerobically in media supplemented with myristoleic 14:1(9c), palmitoleic 16:1(9c), oleic 18:1(9c), linoleic 18:2(9,12c), gamma-linolenic 18:3(9,12,15c) or eicosenoic 20:1(11c) acid. Cells from exponential-phase cultures contained approximately the same proportions of the major phospholipid classes, namely phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine, the greatest differences being detected in cells grown in the presence of 14:1(9c) or 20:1(11c) acids. The extent to which phospholipids from cells were enriched with residues of the exogenously supplied acid varied from 52% in cells grown in the presence of 14:1(9c) acid to 13% in cells grown in media supplemented with 20:1(11c) acid. Analysis of the fatty-acyl composition of the four major phospholipid classes revealed that the degree of unsaturation varied considerably in three of the classes, while phosphatidylinositol conserved a high degree of saturation. The possible significance of the latter finding in relation to the physiological role of phosphatidylinositol in the plasma membrane is discussed.     

SOME ASPECTS OF THE STRUCTURE AND FUNCTION OF THE YEAST PLASMA MEMBRANE

The permeation of many compounds into the yeast cell is largely regulated by the plasma membrane according to their lipid solubility and degree of dissociation. Thus the permeation rate of the fatty acids and α-keto acids is proportional to their relative lipid solubility. The highly dissociated and poorly lipid-soluble di- and tri-carboxylic acids and halogenated acetic acids permeate only very slowly; the impermeable α-ketoglutaric acid becomes easily permeable when made lipid-soluble by esterification. The lipid composition of the plasma membrane can thus be of decisive importance in regulating the movement of different compounds into and out of the yeast cell. Lipid analyses revealed that anaerobiosis clearly affected the neutral lipid composition of the plasma membrane. The aerobic membrane contained more unsaturated fatty acids, mainly palmitoleic and oleic acids, more total sterol, much more ergosterol and much less squalene. The principal sterol in the aerobic membrane, ergosterol, was mainly in the free form, whereas zymosterol and other minor sterols were predominantly esterified. In contrast, the anaerobic membrane contained small amounts of biosynthetic sterol precursors of ergosterol, and was clearly richer in saturated fatty acids having a greater variation in chain length. Both plasma membranes contained a considerable amount of triacylglycerols.     

Acid Washing and Serial Repitching a Brewing Ale Strain of Saccharomyces cerevisiae in High Gravity Wort and the Role of Wort Oxygenation Conditions†

Acid washing pitching yeast is an effective method for removing bacterial contamination, but if the yeast is washed incorrectly decreased fermentation performance and beer quality problems may result. Various factors can affect the acid resistance of yeast strains during brewery fermentations. Yeast from shaking flask experiments was more resistant to the combination of high gravity and acid washing conditions than yeast cropped from static fermentations. Yeast harvested from static high gravity wort (20° Plato; 1.083 OG) fermentations was more adversely affected by acid washing than yeast from standard gravity (12° Plato; 1.048 OG) wort. Wort oxygenation resulted in enhanced yeast fermentation performance and healthier yeast crops when yeast was serially repitched into 20° Plato wort. Yeast cropped from fermentations with air saturated high gravity wort responded poorly when acid washed. These results suggest that the structure of the plasma membrane particularly the sterol and fatty acid composition, may have an important role in tolerating high gravity wort and acid washing conditions.     

Effect of chemical treatment on the fatty acid composition of european cucumber fruit during cold storage

Mature green European cucumber fruits (Cucumis sativus L. cv. ‘V-5’), grown in the greenhouse, were treated with butylatedhydroxytoluene (BHT) and calcium chloride, stored at 4°C for 7 days and transferred to 20°C for another 7 days. There were no visible symptoms of chilling injury on cucumbers during cold storage, but surface pitting and shrinking started 2 days after fruits had been transferred to 20°C. Total lipid content was not affected by chilling or chemical treatment, but changes in the lipid classes were observed. Neutral lipids were increased and phospholipids decreased. Laurie and myristic acids were decreased by chilling and chemical treatment, and palmitic acid increased in each lipid class with BHT treatment. Linoleic acid was increased by CaCl₂ treatment in each fraction. Linolenic acid response varied with chilling and chemical treatment. The unsaturation ratio of 18-carbon acids was increased for total lipids and phospholipids.     

The origin of free fatty acids formed in frozen cape hake mince (Merluccius capensis,castelnau) during cold storage at −18°C

Hake mince was stored at ?18°C and samples were withdrawn at intervals during a 300-day period. The extracted lipids were examined for free fatty acid (FFA) and phosphorus (P) content. Total FFA contents were corrected for a phospholipid contribution and converted into genuine FFA contents. Using these genuine FFA contents and the knowledge that the loss of one mole of lipid-P produces two moles of FFA made it possible to calculate the separate contribution of the phospholipids and the neutral lipids to the FFA formed on storage. It was found that FFA originated from both phospholipids and neutral lipids and after an initial rapid surge of FFA formation from both sources the rates declined and became virtually constant. The results for the Cape hake are compared with literature data of the Atlantic cod and the Baltic herring.     

Effect of fat-enriched diets on rabbit meat fatty acid composition

The effects of beef tallow-, soya and sunflower olein- and soya bean oil-enriched (3%) diets on the chemical and fatty acid composition of total, a polar and polar lipids of rabbit meat have been studied. No significant differences (P > 0.05) in the meat chemical composition were observed between groups. However, a large effect of the diet on the total and apolar lipid fatty acids was found, with C18:1 and C18:2 the most affected fatty acids. The influence of the diets on the fatty acids of the polar fraction was less marked. It is concluded that the enrichment of the rabbit diet with either soya and sunflower oleins or soya bean oil allows the production of rabbit meat with a higher unsaturation degree than is obtained by using conventional diets, which constitutes an important nutritional benefit to the human being.     

传统金华火腿加工过程中皮下脂肪的变化

分别提取0、32d、60d、160d、240d的金华火腿中的皮下脂肪,分析其甘油酯、磷脂、游离脂肪酸的含量和脂肪酸组成。结果表明:甘油酯的含量从95.7%减少到85.4%,游离脂肪酸的含量从2.1%增加到14.3%,磷脂的含量没有发生显著性变化;甘油酯中的SFA有显著性变化,MUFA和PUFA无显著性变化;磷脂中的SFA、MUFA和PUFA都没有显著性变化;游离脂肪酸中,PUFA的含量显著减少,MUFA的含量减少,但其变化不显著,SFA的含量显著增加。     

Changes in sterol and phospholipid composition of apples during storage at low temperature and low oxygen concentration

Free sterol and phospholipid in the cortical tissue of apple were determined during storage of the fruits in air at 12 and 3.5°C and in 2 kPa O₂ (98 kPa N₂) at 3.5°C. In air at 12°C, the sitosterol content declined slightly (about 4%) during fruit ripening whilst phospholipid increased about 8%. At 3.5°C in air and 2 kPa O₂, sitosterol content increased by 16% and phospholipid by 25–31%. The increase in phospholipid in 2 kPa O₂ occurred more slowly than in air. Transfer of apples to air after 33 or 64 days in 2 kPa O₂ led to rapid accumulation of phospholipid in the fruit (20% and 10%, respectively) compared with apples maintained in 2 kPa O₂. An increase in concentration of phosphatidylcholine (PC) accounted for most of the change observed in total phospholipid.     

Changes in the composition of the fatty acids and aldehydes of meat lipids after heating

The effects of heating at 132°C on the fatty acids and fatty aldehydes of neutral lipids and phospholipids of lean beef, veal, lamb, pork and chicken were studied. Heating caused hydrolysis of the plasmalogens in the phospholipids, and varying amounts of the liberated fatty aldehydes were recovered in the neutral lipid fractions. Beef phosphatidyl choline lost more polyunsaturated fatty acids than that of the other meats. Beef and veal phosphatidyl ethanolamine lost more polyunsaturated fatty acid than that of lamb, pork or chicken, but the effect was obscured by the influx of fatty acids from elsewhere into this fraction after heating.     

Chemical constituents of some basidiomycetes

The sterol, fatty acid and free amino acid (FAA) contents of some Basidiomycetes were determined. The overall sterol distribution was similar to that of other mushrooms, with ergosterol as the predominant sterol accompanied by the other closely related sterols. The mushrooms examined also contained high levels of fatty acids of which linoleic is the most prominent. Glutamic acid, valine and proline were the dominant FAA.