Biomedical subjects
Publications and source records attributed to E M Dikanskaia.
The formation of ergosterol by the Candida yeast was studied using glucose, n-paraffins, a mixture of organic acids and inedible sugars. Yeast of different species and strains showed a similar content of ergosterol which made, as a rule, 0.4--0.5%. The amount of ergosterol remained relatively stable with varying cultivation conditions and decreased 1.5--2 times with a temperature increase.
Candida tropicalis IBFM 303 is capable of the active production and liberation of flavins during the oxidation of solid paraffins with the carbon chain consisting of 20 carbon atoms and more. Unlike other known strains, this strain does not accumulate considerable amounts of the vitamin neither on media containing liquid n-paraffins not on media with glucose, even under the conditions of iron deficiency.
Comparative studies of the process of possible overproduction of flavins by cultures with different flavinogenous activity grown on media with hydrocarbons and glucose have been carried out. The strains with a high flavinogenous activity, Candida guilliermondii and Torulopsis famata O-3, produced more flavins on media containing hydrocarbons than the cultures with a low flavinogenous activity. At a high content of iron in the medium, which is unfavourable for overproduction of riboflavin the rate of flavinogenesis is higher on hydrocarbons than on sugars, especially on alkanes with a longer chain in the strain O-3. Under the conditions of iron deficiency, the activity of flavinogenesis is higher on glucose in the case of both cultures. Iron deficiency in media containing hydrocarbons and their oxygenated derivative (cetyl alcohol, palmitic and acetic acids) has no such effect on the production of flavin by T. famata O-3 as in the glucose containing media. On media with ethanol, overproduction of the vitamin by the strain O-3 obeys the same relationships as on media with glucose. Possible factors that may have effect on the elevated synthesis are discussed.
Methylotrophic yeasts Candida boidinii and Hansenula polymorpha requiring thiamine and biotin accumulate more flavins in the cells during growth on media containing methanol than during oxidation of ethanol and glucose, at the account of increased production of FAD whose percentage in the total flavin content of the cell rises sharply. The level of flavin production depends on growth conditions: the intracellular content of flavins and FAD during utilization of methanol by the yeast cells is higher under conditions of continuous cultivation than in periodic cultures. The content of NAD, another coenzyme of the respiration chain, in the cells during their growth on media containing methanol almost does not differ from its concentration in the cells cultivated on media containing glucose and ethanol. Elevated production of flavins and FAD by the yeast cells on media containing methanol may be caused by an increased requirement in FAD and its specific participation in the first stage of methanol oxidation.
The growth of Candida guilliermondii on media with glucose and acetate is described by statistical functions for cell volume (size) distribution. Special instrument has been used to measure the volume of cells and volume distributions. Changes in the morphological structure of populations (both in the average size of cells and in the extent of the size heterogeneity) were detected throughout the whole period of the cultural growth including the exponential phase. These changes hardly differed during the growth on media with glucose or with acetate. The content of flavins in cells also varied in the course of periodic growth. Their total level in cells, as well as the level of FAD, was higher in the exponential phase of growth than during the subsequent phases. Changes in the intracellular level of flavins were found also in yeast populations synchronized by nitrogen limitation.
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