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Biomedical subjects

K Beran

Publications and source records attributed to K Beran.

At least 19 recordsLinked to original sources
PubMed1987

Effect of ammonium ions on delta 5,7-sterol synthesis in Saccharomyces cerevisiae.

The effect of ammonium concentration in the medium on delta 5,7-sterol synthesis was examined. Higher concentrations of this nitrogen source in the medium decreased sterol synthesis and accumulation during growth. An intermittent supply with ammonium resulted in a proportional synthesis of delta 5,7-sterols and biomass. The carbon to nitrogen molar ratio of greater than or equal to 40 allowed the maximum accumulation of delta 5,7-sterols with our strain of baker's yeast.

Ammonia↗
PubMed1986

Fed-batch cultivation of Saccharomyces cerevisiae with increased content of delta 5,7-sterols.

Cultivation of Saccharomyces cerevisiae with a linear nutrient feed was used to test the validity of a mathematical model describing changes in the physiological state of the culture. Markers of these changes were the concentrations of proteins and delta 5,7-sterols in yeast dry mass. The model was used to optimize the production of these sterols with regard to the magnitude and composition of nutrient feed.

Computers↗
PubMed1985

Ergosterol synthesis and population analysis of a fed-batch fermentation in Saccharomyces cerevisiae.

Saccharomyces cerevisiae with an increased content of ergosterol or delta 5,7-sterols, growing on a molasses medium with a feed of ethanol and (NH4)2HPO4, was analyzed as to the age of cell population. The analysis was done by centrifugation in a dextran gradient and by a fluorescence-microscopic technique. In the phase of batch fermentation at a mean specific growth rate of 0.22 h-1 daughter cells contained less than 1% ergosterol while the ergosterol content of mother cells depended on the time of cultivation, a maximum level (4%) being found after two generation times. In the fed-batch phase at a mean growth rate of 0.052 h-1, both daughter and mother cells contained about the same amount of ergosterol (4.7-5.5%). Differences between daughter and mother cells are discussed in view of the relationship between the growth rate and the growth cycle.

Ergosterol↗
PubMed1980

Preparation of zymosan from yeast cell walls.

Cell walls of the yeast Saccharomyces cerevisiae after disintegration and protoplasm removal by centrifugation and repeated washing were suspended in 0.5 M Na2HPO4, pH 7.8-8.0, as a 5% or 10% suspension, depending on the mode of heating. The suspension was boiled for 3 h, purified by repeated washing with water and ethanol and dried. The yield was approximately 1.8% of the starting amount of pressed commercial baker's yeast.

Cell Wall↗
PubMed1979

Activation of proteolytic enzymes during autolysis of disintegrated baker's yeast.

Disintegration substantially accelerates autolysis of yeast cells. Three proteases (A, B, and C) take part in the autolytic process, protease A being the activator of the other two enzymes. The role of proteases B and C in the process depends on temperature. At 40 degrees C both proteases are active while at 50 degrees C the major role is played by protease C. At 40 degrees C NaCl acts as inhibitor while at 50 degrees C it activates the process.

Hydrogen-Ion Concentration↗
PubMed1975

The chitin-glucan complex of Saccharomyces cerevisiae. III. Electron-microscopic study of the prebudding stage.

Differentiation of the cell wall of Saccharomyces cerevisiae at the site of the future bud was followed. A lentil-like structure originates on the inner side of the cell wall during the first phase. At the same time, an electron-dense layer occurs at the boundary between the inner layer of the cell wall and the lentil-like structure. During the second phase granular material is accumulated at the lower side of the lentil-like structure. During the third phase the lentil-like structure is split apart due to proliferation of the granular material resulting in formation of the base of the encircling region. The marked electron-dense layer observed from the first phase is attached to the surface of the encircling region during differentiation of the latter. During the budding proper the outer layers of the cell wall protrude and the end of the encircling region, together with the adjacent electron-dense layer, acquire their definitive appearance of rings, observed as marked electron-transparent and electron-dense tears on ultrathin sections.

Cell Division↗
PubMed1969

Disintegration of microorganisms and preparation of yeast cell walls in a new type of disintegrator.

Microbial cells were disintegrated in a new type of rotary disintegrator with a disc stirrer by a combination of shear force layers, collisions, and rolling of glass beads which were brought into motion by the stirrer. The rate of disintegration at a given dry bed volume of Ballotini beads and a given volume of cell suspension is proportional to the peripheral velocity of the stirrer up to 18 m/sec. Horizontal arrangement of the stirrer increases the effectiveness about five times; 100% disintegration of yeast cells was achieved under optimal conditions within 72 sec at a concentration of 3.5g (dry weight)/100 ml of suspension, and within 96 sec at a concentration of 10.5g (dry weight)/100ml. At 17.5 g (dry weight)/100 ml, the stirrer began to slip. The cell walls of yeast were obtained at the desired degree of crushing and the course of purification was determined by infrared spectral analysis.

Cell Wall↗
PubMed1966

Structural changes in the cell wall of Schizosaccharomyces pombe during cell division.

Streiblová, Eva (Czechoslovak Academy of Sciences, Prague, Czechoslovakia), I. Málek, and K. Beran. Structural changes in the cell wall of Schizosaccharomyces pombe during cell division. J. Bacteriol. 91:428-435. 1966.-Individual stages of growing and dividing cells of Schizosaccharomyces pombe were studied by means of fluorescence and electron microscopy with the use of metal-shadowed isolated walls, replicas, and ultrathin sections. Vegetative cells were found to contain division scars (six at the most); their formation and structure are described. More data on the growth of arthrospores were obtained. New structural observations were made on the architecture of the cell wall (original wall ring, polar cell wall, plug wall band, additional wall ring). Structural changes of cell surfaces and lateral walls during fission are represented schematically to the fourth generation. The question of origin of the septum is discussed, and on this basis the entire structure of the cell wall is interpreted.

Ascomycota↗
PubMedDate not supplied

[Cytomorphologic characteristics of Saccharomyces cerevisiae and Candida utilis as an index of the physiologic state of the culture].

The dimensions of daughter cells without scars, and of mother cells with 1--4 scars, of Saccharomyces cerevisiae and Candida utilis were studied in the one-stage chemostat at D equal to 0.05, 0.1, 0.25, and 0.35 hr-1. The average dimensions of the cells increased with the specific growth rate. At low values of the specific growth rate, "immature" daughter cells separate and attain reproductive ability as independent individual organisms. A twofold increase in the biomass of yeast cells occurs at the account of growth of the buds and small daughter cells.

Candida↗