Effect of stress on the composition of yeast lipids

Pigmented (Rhodotorula glutinis) and nonpigmented (Lipomyces starkeyi) yeasts were studied. Exogenous stressors (UV irradiation and methylene blue) were shown to change the composition of yeast lipids (especially the ratio of unsaturated fatty acids) and to increase the content of lipid peroxidation products formed (particularly in nonpigmented yeasts). In carotene-synthesizing yeasts, these stressors decreased the amount of carotenoids produced and did not affect the ratio between carotenoid pigments (beta-carotene, torulene, and torularhodin).     

Effects of excess dietary phenylalanine on composition of cerebral lipids

Abstract— Concentrations in whole rat brains of lipids (total lipids, phospholipids, galactolipids, cholesterol, plasmalogens) and of proteolipid protein were not altered after feeding for 2 and 6 weeks of diets containing 5 per cent excess l -phenylalanine. After 2 weeks of diet with 7 per cent excess l -phenylalanine there was a slight reduction (5–10 per cent) in the concentrations in whole brain of cholesterol and galactolipids. No significant effects were noted in cerebral hemispheres after 3 weeks of diets with 7 per cent excess l -phenylalanine. In the 5 and 7 per cent supplemented groups of animals, the total amounts of the various lipids were initially reduced to levels which were within 10 per cent of those in diet-matched controls. The results for rats indicate that after 3 weeks of age only very moderate effects on accumulation of cerebral lipids can be produced by excess dietary l -phenylalanine fed at the most toxic levels of supplementation, while lower levels of dietary supplementation are without effect. The results suggest further that the more mature brain is resistant to alteration of deposition of myelin lipids by high levels of phenylalanine.     

Resistance to cellobiose lipids and specific features of lipid composition in yeast

The significance of the fatty acid composition and ergosterol content in cells for resistance to cellobiose lipids has been investigated in the cells of mutant Saccharomyces cerevisiae strains that are unable to produce ergosterol or sphingomyelin and in the cells of microorganisms that produce cellobiose lipids. S. cerevisiae mutants were shown to be less sensitive to cellobiose lipids from Cryptococcus humicola than the wild-type strain, and the strains that produced cellobiose lipids were virtually insensitive to this compound as well. The sensitivity of Pseudozyma fusiformata yeast to its own cellobiose lipids was reduced under conditions that favored the production of these compounds. No correlation between the content of ergosterol and sensitivity to cellobiose lipids was observed in S. cerevisiae or in the strains that produced cellobiose lipids. The ratio between the levels of saturated and unsaturated fatty acids in the cells of the mutant strains was correlated to the sensitivity of the cells to cellobiose lipids.     

Relationship between the fatty acid composition of lipids and the viability of dried yeast Saccharomyces cerevisiae

Summary The fatty acid composition of the total lipids and phospholipids of intact and convectively dried yeast has been studied and an increase has been detected in the degree of unsaturation of fatty acids during dehydration. The validity of the inverse relation between the viability of the yeast population during dehydration and rehydration and the degree of unsaturation of the fatty acids has been demonstrated by regression analysis. The results may help to predict the viability of dried yeast.     

Effects of brewer's yeast on glucose tolerance and serum lipids in Chinese adults

This study was designed to investigate the supplemental effects of brewer's yeast on serum glucose and lipids in Chinese adults. Twenty-two participants (8 males and 14 females) were recruited from Pingtung city. Mean age of the group was 51 yr, and fasting values of total cholesterol and glucose were from 3.21 to 6.90 and 4.3 to 6.2 mmol/L, respectively. Before supplementation, a 75 g oral glucose load was administered after an overnight (9 h) fast. Blood was drawn before and at 30, 60, 90, and 120 min after the glucose load. The subjects were randomly assigned into either brewer's yeast or torula yeast group and consumed 10 g yeast powder daily for 12 wk. Brewer's yeast demonstrated a beneficial effect on decreasing serum triacylglycerol values (p<0.05). The brewer's yeast supplemented group had an increment at 0 min (p<0.01) and significant decrements at 60 (p<0.05) and 90 (p<0.01) min of oral glucose tolerance test (OGTT). However, after 12-wk supplementation, torula yeast increased glucose values at both 0 and 30 min (p<0.05) after a glucose load. Brewer's yeast and torula yeast addition significantly altered glucose concentrations at 60 min after the glucose dosage (p<0.05). Brewer's yeast had significantly decreasing effects on insulin output both at 90 (p<0.05) and 120 min (p<0.01) after the glucose load. Likewise, serum insulin contents decreased at 90 min (p<0.01) after supplementation in the group given torula yeast. Brewer's yeast supplementation had beneficial effects both on serum triacylglycerol and on 60-min and 90-min glucose values of OGTT.     

Modification of the fatty-acid composition in lipids of the oleaginous yeast Apiotrichum curvatum by intraspecific spheroplast fusion

Summary Modification of the fatty-acid composition in lipids of the oleaginous yeast Apiotrichum curvatum has been achieved by means of spheroplast fusion between a methionine auxotrophic mutant and an unsaturated fatty acid mutant. Fusion products were a result of nuclear hybridization as determined by flow-cytometric DNA-content analyses. A broad range of fatty acid composition was observed in lipids of different hybrids. In general the level of saturated fatty acids in lipids of hybrid strains is higher than in wild-type A. curvatum and in some hybrids even approaches cocoa butter. Intraspecific spheroplast fusion seems a promising approach for the production of cocoa butter equivalents.     

Lipid composition of the yeast

Summary The lipids of two strains of Lipomyces kononenkoae, grown in batch culture, were extracted and analysed. The major lipids present were phospholipids, free sterols, esterified sterols, and triacylglycerols. Phospholipid analysis indicated that phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol were the major ones. The fatty-acyl residues were C₁₂-C₁₈ and contained 67–74% unsaturated residues. Polyunsaturated residues accounted for 15% and 30% in L. kononenkoae CBS 2514 and L. kononenkoae CBS 5608, respectively. Analysis of the fatty-acyl residues of a low-density vesicle fraction obtained from sphaeroplasts of L. kononenkoae CBS 2514 was carried out and the results are discussed in relation to plasma membrane synthesis. The suitability of L. kononenkoae for production of single-cell protein is also discussed.     

Effects of pH and temperature on the composition of polar lipids in Thermoplasma acidophilum HO-62

Thermoplasma acidophilum HO-62 was grown at different pHs and temperatures, and its polar lipid compositions were determined. Although the number of cyclopentane rings in the caldarchaeol moiety increased when T. acidophilum was cultured at high temperature, the number decreased at low pHs. Glycolipids, phosphoglycolipids, and phospholipids were analyzed by high-performance liquid chromatography with an evaporative light-scattering detector. The amount of caldarchaeol with more than two sugar units on one side increased under low-pH and high-temperature conditions. The amounts of glycolipids increased and those of phosphoglycolipids decreased under these conditions. The proton permeability of the liposomes obtained from the phosphoglycolipids that contained two or more sugar units was lower than that of the liposomes obtained from the phosphoglycolipids that contained one sugar unit. From these results, we propose the hypothesis that T. acidophilum adapts to low pHs and high temperatures by extending sugar chains on their cell surfaces, as well as by varying the number of cyclopentane rings.     

Effects of pressure stress on the fission yeast Schizosaccharomyces pombe cold-sensitive mutant nda3

To investigate the influence of pressure stress on the cell cycle of Schizosaccharomyces pombe, we used a cold-sensitive nda3-KM311 mutant which arrests cell division at a step similar to the mitotic prophase, proposed by Hiraoka and colleagues (Cell 39 (1984) 349-358), under the restrictive temperature, 20 degrees C. The nda3-KM311 cells were first aerobically grown at 30 degrees C, transferred to 20 degrees C for 4 h and shifted to a permissive temperature of 36 degrees C for 15 min. The cells were treated with 100-200 MPa pressure and studied by electron and fluorescence microscopy. At 100 MPa, the nuclear membrane was damaged and the matrix of mitochondria had an electron-dense area. At 150 MPa, the nuclear membrane was broken over broad areas; numerous small vacuoles had fused into large pieces. Actin patches were concentrated in the central region and actin rings were seen in the 20 degrees C-grown cells. Even at 100 MPa, specific actin distribution was lost. Although at 100 MPa, long and fine actin cables were seen all over the cells, large actin patches and the actin rings remained in the center of the cell. They changed into thick and short cables at 150 MPa and above 200 MPa they decomposed but the actin ring was visible even with faint fluorescence. Immunoelectron microscopic observation confirmed this phenomenon.     

Effects of N-glycosylation and inositol on the ER stress response in yeast Saccharomyces cerevisiae

IRE1 and HAC1 are essential for the unfolded protein response in the endoplasmic reticulum (ER). IRE1- and HAC1-disruptants require high concentrations of inositol for its normal growth. The ALG6, ALG8, and ALG10 genes encode the glucosyltransferases necessary for the completion of the synthesis of the lipid-linked oligosaccharide used for the asparagine-linked glycosylation of proteins in that order. Here we show that, given a combination of the hac1 defect with a disruption of ALG6, ALG8, and ALG10, no strains grow on inositol-free medium. However, the growth defect of the hac1-alg10 double disrupted was partially, but significantly, suppressed by the addition of inositol to the medium. These results indicate that inositol, according to the numbers of glucose residues in the oligosaccharide, plays an important role in the stress response and quality control of glycoproteins in the ER.     

酵母微生物油脂的生物合成研究

摘要：目的 微生物油脂可作为制备绿色能源生物柴油的原料。对酵母微生物油脂的生物合成方法进行研究。方法 以斯达油脂酵母Lipomyces starkeyi AS 2.1560为菌种进行微生物油脂生物合成。首先获得大量细胞,将细胞收集后,转移至葡萄糖溶液中进行油脂合成。结果 斯达油脂酵母可在不含有其他营养成分的葡萄糖溶液中快速合成油脂,细胞油脂含量可达到细胞干重的60%以上。菌龄对油脂生成影响不明显,糖浓度过高抑制油脂生成,40 g/L葡萄糖溶液中60 h合成油脂最多,达到65.2%,并有进一步积累的可能,在（0.5～6）×108个/mL,接种细胞的密度越大,油脂合成能力越低。合成油脂成分主要为棕榈酸和油酸。结论 斯达油脂酵母细胞增殖与油脂生物合成可分开进行,其油脂成分与普通动植物油脂成分相似。     

"Oxygen regulation" of the respiratory chain composition in the yeast Debaryomyces hansenii under multiple stress

It was shown that two stress factors, hypoxia and hyperosmotic shock, if applied simultaneously to the yeast Debaryomyces hansenii, display an antagonistic mode of interaction, which results in an increased degree of halophily of this microorganism under microaerobic conditions. Studies of the effects of respiration inhibitors (sodium azide and salicyl hydroxamic acid, SHA) and of the pattern of changes in the composition of the respiratory chain of Debaryomyces hansenii under the stated stress conditions led to the suggestion of three (or four) chains of electron transfer functioning simultaneously in the cell: the classical respiratory chain involving cytochrome-c oxidase, an alternative respiratory chain involving a cyanide- and azide-resistant oxidase, and additional respiratory chains involving oxidases resistant to salt, azide and SHA. Thus, the antagonistic mode of interaction between hypoxia and hyperosmotic shock results from the redirection of the electron flow from the salt-susceptible respiratory systems to the salt-unsusceptible ones encoded by "the hypoxia genes" and activated (induced) under microaerobic conditions.     

Effects of bonellin on lipids

A comparative study was conducted on the ability of bonellin, the green pigment of Bonellia viridis, and hematoporphyrin to induce photoperoxidation of lipids in solutions and in erythrocyte ghosts. The inhibiting effect of two free radical scavangers, acetyl-homocysteine-thiolactone and meclofenoxate, indicates that bonellin-induced lipid peroxidation involves free radical production. The relation between bonellin and defence mechanism of Bonellia viridis is discussed.