Перегляд за Автор "Kovalenko, M."

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Enhanced synthesis of the exopolysaccharide ethapolan by acinetobacter sp. 12S grown on a mixture of substrates
(2003) Pirog, Tatiana; Kovalenko, M.; Kuzminska, Yu.; Krishtab, T.
Enhanced synthesis of the exopolysaccharide ethapolan by Acinetobacter sp. 12S was observed when the bacterium was grown on a mixture of two energetically nonequivalent substrates (ethanol and glucose) taken in a molar proportion of 3.1 : 1. The efficiency of carbon transformation into EPSs was maximum when sodium ions were absent in the medium, the concentration of nitrogen source was reduced to 0.3–0.45 g/l, and the inoculum was grown on ethanol. Such conditions provided an increase in the maximum specific growth rate and its attainment in earlier cultivation terms. Molasses as a substitution for glucose was inefficient. The activities of the key enzymes of C2 metabolism in Acinetobacter sp. 12S cells grown on the substrate mixture were 1.1 to 1.7 times lower than they were during growth on ethanol alone. The activity of isocitrate lyase in cells grown on the substrate mixture declined to an even greater extent (by 4–7 times), indicating that the role of the glyoxylate cycle in such cells is insignificant. Установлены условия культивирования штамма Acinetobacter sp. 12S - продуцента микробного экзополисахарида (ЭПС) этаполана, позволяющие интенсифицировать синтез ЭПС на смеси двух энергетически-неравноценных субстратов (этанол и глюкоза в молярном соотношении 3,1:1). Наиболее высокая эффективность трансформации углерода субстратов в ЭПС обеспечивалась при отсутствии в среде катионов натрия, снижении концентрации источника азотного питания до 0,3-0,45 г/л, использовании посевного материала, выращенного на этаноле. Культивирование продуцента в таких условиях сопровождалось также увеличением максимальной удельной скорости роста и смещением времени ее достижения в более раннюю ростовую фазу. Установлено, что глюкоза в смешанном субстрате не может быть заменена на мелассу. При выращивании Acinetobacter sp.12S на смеси субстратов активность ключевых ферментов С2-метаболизма снижалась в 1,1-1,7 раза по сравнению с культивированием на этаноле. Более заметным (в 4-7 раз) было снижение изоцитратлиазной активности, что может свидетельствовать о незначительной роли глиоксилатного цикла в метаболизме бактерий при росте на смеси С2-С6-субстратов.
Exopolysaccharide Production and Peculiarities of C6-Metabolism in Acinetobacter sp. Grown on Carbohydrate Substrates
(2002) Pirog, Tatiana; Kovalenko, M.; Kuzminska, Yu.
An Acinetobacter sp. strain grown on carbohydrate substrates (mono- and disaccharides, molasses, starch) was shown to synthesize exopolysaccharides (EPS). Glucose catabolism proved to proceed via the Embden–Meyerhof–Parnas and Entner–Doudoroff pathways. Pyruvate entered the tricarboxylic acid cycle due to pyruvate dehydrogenase activity. Pyruvate carboxylation by pyruvate carboxylase was the anaplerotic reaction providing for the synthesis of intermediates for the constructive metabolism of Acinetobacter sp. grown on C6-substrates. The C6-metabolism in Acinetobacter sp. was limited by coenzyme A. Irrespective of the carbohydrate growth substrate (glucose, ethanol), the activities of the key enzymes of both C2- and C6-metabolism was high, except for the isocitrate lyase activity in glucose-grown bacteria. Isocitrate lyase activity was induced by C2-compounds (ethanol or acetate). After their addition to glucose-containing medium, both substrates were utilized simultaneously, and an increase was observed in the EPS synthesis, as well as in the EPS yield relative to biomass. The mechanisms responsible for enhancing the EPS synthesis in Acinetobacter sp. grown on a mixture of C2- and C6-substrates are discussed.
Intensification of exopolysaccharide synthesis by Acinetobacter sp. on an ethanol–glucose mixture: aspects related to biochemistry and bioenergetics
(2003) Pirog, Tatiana; Kuzminska, Yu.; Kovalenko, M.
The possibility of intensifying the synthesis of microbial exopolysaccharides (EPS) by a strain of Acinetobacter sp. grown on a mixture of two substrates nonequivalent in terms of bioenergetics (ethanol + glucose) was shown. Based on theoretical calculations of the energy requirements for biomass and EPS synthesis from the energy-deficient substrate (glucose), the supplementary concentration of the energy-excessive substrate (ethanol) was determined that prevents the loss of glucose carbon that occurs when glucose is oxidized to CO2 to obtain energy for the processes of constructive metabolism. This made it possible to increase the efficiency of conversion of the substrate carbon to EPS. The introduction of ethanol into glucose-containing medium at a molar ratio of 3.1 : 1 allowed the amount of the EPS synthesized to be increased 1.8- to 1.9-fold; their yield relative to biomass increased 1.4- to 1.7-fold, and the yield of EPS relative to the substrate consumed increased 1.5- to 2-fold as compared to growth of the producer on single substrates. These results form the basis for the development of new technologies for obtaining secondary metabolites of practical value with the use of mixed growth substrates. Показана можливість інтенсифікації синтезу мікробних екзополісахаридів (ЕПС) при вирощуванні штаму Acinetobacter sp. на суміші двох енергетично-нерівноцінних субстратів (етанол + глюкоза). На основі теоретичних розрахунків енергетичних потреб синтезу біомаси та ЕПС на енергетично-дефіцитному субстраті (глюкоза) визначена "доповнююча" концентрація енергетично-надлишкового субстрату (етанол), що дозволяє заповнити втрати вуглецю глюкози при окисленні її до СО2 з метою отримання енергії для процесів конструктивного метаболізму, і підвищити ефективність конверсії вуглецю використовуваних субстратів в ЕПС. Введення етанолу в середу з глюкозою в молярному співвідношенні 3,1:1 дозволило збільшити кількість синтезованих ЕПС в 1,8-1,9 рази, їх вихід по відношенню до біомаси - в 1,4 - 1,7 рази, вихід ЕПС від субстрату - в 1,5 - 2 рази в порівнянні з вирощуванням продуцента на моносубстратах. Отримані результати є основою для створення нових технологій одержання практично цінних вторинних метаболітів при використанні змішаних енергетично-нерівноцінних ростових субстратів.
Physicochemical Properties of the Microbial Exopolysaccharide Ethapolan Synthesized on a Mixture of Growth Substrates
(2004) Pirog, Tatiana; Kovalenko, M.; Kuzminska, Yu.; Votselko, S.
Some physicochemical properties of the microbial exopolysaccharide (EPS) ethapolan synthesized by Acinetobacter sp. 12S depended on whether the producer was grown on a mixture of ethanol and glucose or on a single substrate. Irrespective of the carbon source in the nutrient medium, the contents of carbohydrates, pyruvic acid, uronic acids, and mineral components in the EPS remained unchanged. The EPS were also identical in their monosaccharide composition: the molar ratio of glucose, mannose, galactose, and rhamnose was 3 : 2 : 1 : 1. EPS with a higher content of fatty acids was synthesized during growth on the mixture of ethanol and glucose. The average molecular mass and the content of high-molecular (M > 2 MDa) fractions were greater in ethapolan produced on the substrate mixture. In the presence of 0.1 M KCl, after transformation into the H+ form, and in the Cu2+–glycine system, solutions of these EPS showed higher viscosity than solutions of EPS synthesized on single substrates. The reasons for the improved rheological properties of the EPS produced on the substrate mixture are discussed.