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I M Gracheva

Publications and source records attributed to I M Gracheva.

17 recordsLinked to original sources
PubMed1987

[Effect of protoplast formation on the antibiotic activity of the Streptomyces fradiae 165 strain--a producer of tylosin].

Streptomyces is characterized by genetic instability evident from high frequency of changes in various properties of secondary metabolites occurring spontaneously or under the influence of certain factors. Protoplast formation is one of such factors. The paper is concerned with the influence of protoplast formation and subsequent regeneration into the mycelial form on antibiotic potency of S. fradiae strain 165. It was shown that protoplast formation led to changes in antibiotic potency of separate colonies and shifts in the potency in the direction of its increasing. The antibiotic potency of certain variants after protoplast formation was 2 to 2.5 times higher than the initial one. Changes due to protoplast formation of S. fradiae strain 165 were not stable and lost after 4-5 passages on agar media. Comparative restriction analysis of total DNA of the variants with different potency levels did not provide detection of changes in the genome of the strains isolated after protoplast formation.

Culture Media↗
PubMed1979

[Effect of higher alcohols on the activity of biosynthetic L-threonine dehydratase from Saccharomyces carlsbergensis brewer's yeast].

The effects of low (1 . 10(-4) M) and high (1 . 10(-3) M) concentrations of n-propanol, isobutanol and isoamylols on the kinetic behaviour of "biosynthetic" L-threonine dehydratase from brewer's yeast S. carlsbergensis 776 were studied. It was concluded that these alcohols control the activity of the first enzyme of the L-threonine biosynthetic pathway.

Alcohols↗
PubMed1977

[Purification and properties of glucoamylase from Endomycopsis sp. 20-9].

Homogenous yeast (Endomycopsis sp. 20-9) glucoamylase was isolated from cultural medium. The homogeneity of the enzyme preparation is demonstrated by means of polyacrylamide gel disc electrophoresis, isofocusing and ultracentrifugation. Amino acid composition, molecular weight (53 000), sedimentation constant (4.3S) and isoelectric point (pI 3.80-3.82) of the enzyme are determined. Glucoamylase is found to be glucoprotein.

Amino Acids↗
PubMed1977

[14C incorporation into lipid fractions of yeast Candida quilliermondii during growth in the presence of different carbon sources].

Kinetics of 14C incorporation into lipid fractions of yeast C. quilliermondii from 1-14C-octadecane and 1,2-14C-acetic acid is studied. Considerable differences, revealed in kinetics and the rate of 14C incorporation into lipid fractions depending on the lipid precursors, draw to the conclusion that the lipid synthesis from octadecane and acetic acid can occur through different pathways. The absence of the competition under the carbon influx into lipid fraction also suggests, that the lipid synthesis from ocetate and carbohydrate takes place simultaneously through two different pathways, which are spatially uncoupled in cell. A presence in yeast cells of two glyoxylate shunts is proposed, which are spatially uncoupled and specific to acetyl residues of different origins.

Acetates↗
PubMedDate not supplied

[Effect of some amino acids on the biosynthesis of glucoamylase by cultured Endomycopsis species].

The effect of amino acids (glutamic, aspartic, beta-alanine, phenylalanine, methionine) on the glucoamylase biosynthesis by Endomycopsis species 20-9 was studied. Monoaminodicarboxylic acids produced a stimulating effect on the glucoamylase synthesis. Their addition at optimal concentrations of 0.2 to 0.4% increased by 54--69% glucoamylase activity of Endomycopsis sp. 20-9 upon submerged cultivation on the medium containing 3% maize extract and 1% starch. An application of this amino acid nutrition during cultivation did not produce a significant effect on the microbial glucoamylase activity.

Amino Acids↗
PubMedDate not supplied

[Effect of growth medium composition of glucoamylase and glycosyltransferase activity of Endomyces fibuliger].

Production of glucoamylase and glycosyltransferase by Endomyces fibuliger was found to depend on sources of carbon and nitrogen nutrition. Starch at a concentration above 0.5% in the medium stimulated biosynthesis of glycosyltransferase but inhibited production of glucoamylase by End. fibuliger 20-9. The rate of growth of the micro-organism increased by a factor of 3.3 with an increase of starch concentration from 0.5 to 6%. Synthesis of glycosyltransferase was repressed by glucose, lactose, sucrose and maltose. Synthesis of glucoamylase was repressed by lactose, sorbose and galactose. Synthesis of glycosyltransferase was stimulated by xylose, sorbose and galactose. Production of glucoamylase was stimulated by xylose and arabinose. Growth of the culture and synthesis of glucoamylase and maltase in the cultural broth were stimulated by an increase in the concentration of maize extract. Biosynthesis of glucoamylase and glycosyltransferase was stimulated by NH4H2PO4.

Ascomycota↗
PubMedDate not supplied

[Effect of carbon composition of the fermented medium on the synthesis of volatile acids by the yeast Saccharomyces carlsbergensis 776].

The effect of glucose, maltose and sucrose on the synthesis of volatile oils during fermentation of model carbohydrate solutions (6, 8 and 11%) by the yeast Saccharomyces carlsbergensis 776 was studied. The composition and concentration of carbohydrates affected the build-up of volatile fatty acids during fermentation. The accumulation of biomass and volatile fraction of fatty acids reached maximum on the medium containing 11% glucose. There was a certain correlation between the biomass synthesis and accumulation of volatile fatty acids, i.e. with an increase in the biomass the content of volatile fatty acids in the medium increased. During fermentation of disaccharide solutions cell multiplication diminished and the fermentation process accelerated. Ethanol, residual sugar and acidity of fermented solutions increased with the initial concentration of carbohydrates. The pH value of the fermented must remained essentially unaltered independent of the sugar amount used.

Culture Media↗
PubMedDate not supplied

[Formation of higher alcohols by Saccharomyces carlsbergensis from branched-chain amino acids and their keto analogs].

A new method of chemical synthesis of alpha-ketoisocaproic acid (the keto analogue of L-leucine) is described. It has been shown that the resting cells of Saccharomyces carlsbergensis 776, in the stationary state of biomass, produce mainly higher alcohols: isobutanol from L-valine and its keto analogue; optically active amylol only from L-isoleucine and its keto analogue; isoamylol only from L-leucine and its keto analogue. "Nonspecific" formation of n-propanol from L-valine, L-isoleucine and their keto analogues, as well as that of isobutanol from L-isoleucine and its keto analogue, has been also found at pH 7.0. Formation of higher alcohols from alpha-keto acids has an acidic pH optimum while that from L-amino acids has a neutral or a weakly alkaline pH optimum. Formation of isobutanol from L-valine is an exception. The dependence of higher alcohol formation on the pH and the kinetics of their accumulation suggest that higher alcohols are produced from L-amino acids in at least three sequential reactions: transamination, decarboxylation of the keto analogue being formed, and reduction of the aldehyde; formation of higher alcohols from alpha-keto acids involves two reactions: decarboxylation and reduction. Transamination and decarboxylation are limiting steps in the process in the former case, and decarboxylation in the latter.

Alcohols↗
PubMedDate not supplied

[Influence of carbon source on lipid biosynthesis by Candida gluilliermondii].

The biosynthesis of lipids by Candida guilliermondii was studied during the growth of the yeast on carbon substrates which resulted in different pathways of lipid biosynthesis. The highest content of lipids was found during the growth on octadecane. The quantitative ratio between fractions of neutral lipids and phospholipids depended on the carbon substrate whereas the quanlitative composition of the fractions remained the same. The fatty acid composition of lipid fractions was studied, and possible pathways of their biosynthesis are discussed. Apparently, the assimilated hydrocarbon is oxidized to acetyl residues in certain structures of the yeast cells while, in other structures, the hydrocarbon substrate undergoes only monoterminal oxidation yielding an aliphatic alcohol and an acid which are directly used in large amounts for the synthesis of wax and triglycerides.

Acetates↗
PubMedDate not supplied

[Effect of the physiological properties of yeast strains on their formation of higher alcohols and aldehydes and on the composition of nitrogen compounds in the fermented wort].

Dynamics of formation of by-products was studied with the following yeast races: Sacch. cerevisiae, strain Odesskaya-14 (baker's yeast); Sacch. vini, strain Prikumskaya 80/9 (wine yeast). The yeast cultures were found to be very similar by the rate of biomass accumulation, ethanol production, and the fractional composition of nitrogen compounds. The concentration of accumulated higher alcohols depended on the mass of yeast cells, their growth rate, and the duration of cultivation.

Aldehydes↗