Перегляд за Автор "Malashenko, Yuri"

Зараз показуємо 1 - 7 з 7

A method for determining the mass-molecular composition of microbial exopolysaccharides
(1993) Votselko, S.; Pirog, Tatiana; Malashenko, Yuri; Grinberg, Tamara
A method of determining the molecular mass composition of microbial exopolysaccharides (EPS) by centrifuging them in a combined density gradient created by NaCl and CsCl solutions and using the molecular mass of dextranes as standards is developed. The process of determining the molecular mass distribution pattern of EPS is simplified and made considerably less time-consuming. This method allows the analysis of native EPS with molecular masses ranging from 13 700 to 2 000 000.
A two-stage cultivation technique for producing microbial exopolysaccaride ethapolan with improved rheological properties
(2001) Pirog, Tatiana; Malashenko, Yuri; Votselko, S.
A two-stage technique was proposed for cultivating producers of microbial exopolysaccharide ethapolan. The practical value of ethapolan is determined by its rheological properties. The use of a formaldehyde-supplemented medium at the second stage of cultivation improved the rheological properties of ethapolan without reducing its yield. This effect of formaldehyde was due to its binding to the exopolysaccharide, which altered the molecular-weight characteristics of the latter and protected cells against the toxic action of formaldehyde. At all stages of its purification, ethapolan had improved rheological properties, suggesting that it was tightly bound to formaldehyde.
Effect of environmental factors on the synthesis and properties of Acinetobacter sp. exopolysaccharides
(1998) Pirog, Tatiana; Grinberg, Tamara; Malashenko, Yuri
Effects of external factors on the synthesis and physicochemical properties of Acinetobacter sp. exopolysaccharides (EPSs), which determine the biological functions of this microorganism, were studied. The cultivation temperature, medium pH, and oxygen concentration in the medium (p02) affected the viscosity of EPS solutions in the presence of monovalent cations, in the H+-form, and in a Cu2+-glycine system. All the EPSs studied were precipitated with heavy metal ions (Cr3+, Cu2+, Pb2+, Cd2+, etc.). No changes in the EPS yield were observed under unfavorable environmental conditions. At high pO2 values (up to 80% of saturation), the maximum specific rates of bacterial growth and EPS synthesis increased. It was suggested that Acinetobacter sp. EPSs perform different biological functions under optimal and nonoptimal conditions.
Ethapolan: a new microbial exopolysaccharide for oil industry
(1995) Grinberg, Tamara; Pirog, Tatiana; Malashenko, Yuri; Vlasov, Sergei A.
Ethapolan, a new high-viscous exopolysaccharide, was obtained in the course of microbial synthesis. Its chemical content and some characteristics of its solutions are explored in the present study. By its structure ethapolan may be considered a polysaccharide of xanthan type. More definitely, as compared to xanthan, the emulsifying efficiency and hydrophobic nature of ethapolan may be attributed to the presence of the fatty acids residues and to 6-desoxysaccharide—rhamnose residues. It was found that a few factors impact the increasing viscosity of ethapolan solutions: first, the presence of the cations; second, low shearing rates; and, finally, low pH values. Ethapolan is resistant to heating. On this basis, it may be concluded that ethapolan appears to be a universal and quite competitive microbial exopolysaccharide for the oil industry.
Isolation and characterization of Acinetobacter sp. mutants defective in exopolysaccharide biosynthesis
(2000) Pirog, Tatiana; Stolyar, S.; Malashenko, Yuri
Nitrosoguanidine-induced mutants ofAcinetobacter sp. defective in exopolysaccharide biosynthesis did not differ from the parent strain in distinguishing physiological and biochemical properties, such as requirements for growth factors, utilization of mono- and disaccharides, and resistance to antibiotics. The genetic relation of parent and mutant strains was shown by 16S rRNA PCR analysis. The comparative study of parent and mutant strains with respect to resistance to unfavorable environmental factors confirmed our hypothesis that Acinetobacter sp. exopolysaccharides perform protective functions. Hybridization experiments revealed the conjugal transfer of plasmid R68.45 from Pseudomonas putida BS228 (R68.45) to mutant but not to the parent Acinetobacter sp. strains. The role of the Acinetobacter sp. exopolysaccharides in providing the genetic stability of this bacterium is discussed. Методом нітрозогуанідінового мутагенезу отримані мутантні штами Acinetobacter sp., Що не утворюють Екзополісахариди (ЄПС). Вихідний і мутантні штами не відрізняються між собою по ряду характерних для цих бактерій фізіолого-біохімічних ознак (потреба в ростових факторах, асиміляція моно-і дисахаридів, стійкість до антибіотиків). Ідентичність вихідного і мутантних штамів встановлена також на основі аналізу їх 16S рРНК. Результати вивчення стійкості клітин вихідного та мутантних штамів до несприятливих факторів підтвердили захисні функції ЕПС Acinetobacter sp. по відношенню до клітин продуцента. При схрещуванні Acinetobacter sp. з Pseudomonas putida BS228 (R68.45) здійснено кон'югатівний перенесення плазміди R68.45 в клітини мутантних (але не початкового) штамів. Обговорюється роль ЕПС Acinetobacter sp. як одного з факторів, що забезпечують генетичну стабільність штаму-продуцента.
Peculiarities of ethanol metabolism in an Acinetobacter sp. Mutant strain defective in exopolysaccharide synthesis
(2002) Pirog, Tatiana; Sokolov, I.; Kuzminska, Yu.; Malashenko, Yuri
Activities of the key enzymes of ethanol metabolism were assayed in ethanol-grown cells of an Acinetobacter sp. mutant strain unable to synthesize exopolysaccharides (EPS). The original EPS-producing strain could not be used for enzyme analysis because its cells could not to be separated from the extremely viscous EPS with a high molecular weight. In Acinetobacter sp., ethanol oxidation to acetaldehyde proved to be catalyzed by the NAD+-dependent alcohol dehydrogenase (EC 1.1.1.1.). Both NAD+ and NADP+ could be electron accepters in the acetaldehyde dehydrogenase reaction. Acetate is implicated in the Acinetobacter sp. metabolism via the reaction catalyzed by acetyl-CoA-synthetase (EC 6.2.1.1.). Isocitrate lyase (EC 4.1.3.1.) activity was also detected, indicating that the glyoxylate cycle is the anaplerotic mechanism that replenishes the pool of C4-dicarboxylic acids in Acinetobacter sp. cells. In ethanol metabolism by Acinetobacter sp., the reactions involving acetate are the bottleneck, as evidenced by the inhibitory effect of sodium ions on both acetate oxidation in the intact cells and on acetyl-CoA-synthetase activity in the cell-free extracts, as well as by the limitation of the C2-metabolism by coenzyme A. The results obtained may be helpful in developing a new biotechnological procedure for obtaining ethanol-derived exopolysaccharide ethapolan. В клетках выращенного на этаноле мутантного штамма Acinetobacter sp., не образующего экзополисахариды (ЭПС), определены активности ключевых ферментов метаболизма этанола. Клетки исходного ЭПС-образующего штамма не могли быть использованы для проведения энзимологических исследований ввиду невозможности их отделения от высоковязкого ЭПС с высокой молекулярной массой. Установлено, что окисление этанола до ацетальдегида у Acinetobacter sp. катализируется НАД+-зависимой алкогольдегидрогеназой (КФ 1.1.1.1.). Акцепторами электронов в ацетальдегиддегидрогеназной реакции являются НАД+ и НАДФ+. Ацетат вовлекается в метаболизм Acinetobacter sp. при участии ацетил-КоА-синтетазы (КФ 6.2.1.1.). Наличие изоцитратлиазы (КФ 4.1.3.1.) свидетельствует о том, что анаплеротической последовательностью реакций, восполняющих пул С4-дикарбоновых кислот в клетках Acinetobacter sp., является глиоксилатный цикл. «Узким» местом метаболизма этанола у бактерий Acinetobacter sp. является вовлечение ацетата в метаболизм, о чем свидетельствует ингибирование окисления ацетата в интактных клетках и активности ацетил-КоА-синтетазы в бесклеточном экстракте ионами натрия, а также лимитирование С2- метаболизма коэнзимом А. Полученные данные являются основой для разработки новой технологии получения экзополисахарида этаполана на основе этанола.
Search for methanotrophic producers of exopolysaccharides
(2001) Malashenko, Yuri; Pirog, Tatiana; Romanovska, V.; Malashenko, Yuri; Sokolov, I.; Grinberg, Tamara
Bacteria that produce exopolysaccharides (EPS) and use methane as the only source of carbon were selected by studying a collection of methanotroph strains: Methylococcus capsulatus E 494, 874, and 3009; M. thermophilus 111p, 112p, and 119p; Methylobacter ucrainicus 159 and 161; M. luteus 57v and 12b; Methylobacter sp. 100; Methylomonas rubra 15 sh and SK-32; Methylosinus trichosporium OV3b, OV5b, and 4e; M. sporium 5,12, A20d, and 90v; and Methylocystis parvus OVVP. Mesophilic methanotroph strains with the ribulose monophosphate way of C1-compound assimilation synthesized EPS more actively than bacteria operating the serine cycle. The dynamics of EPS synthesis by methanotrophs during chemostat cultivation was studied.