Biosynthetic features and properties of xylose isomerases from Arthrobacter nicotianae, Escherichia coli, and Erwinia carotovora subsp. atroseptica

The characteristics of xylose isomerase biosynthesis in the bacteria Arthrobacter nicotianae BIM B-5, Erwinia carotovora subsp atroseptica jn42xylA, and Escherichia coli HB101xylA have been studied. The bacteria produced the enzyme constitutively. Out of the carbon sources studied, D-glucose and D-xylose were most favorable for the biosynthesis of xylose isomerase in E. carotovora subsp. atroseptica, but the least appropriate in terms of the enzyme production efficiency in E. coli. Minimum and maximum levels of xylose isomerase formation in A. nicotianae were noted, respectively, during D-xylose and sucrose utilization. An addition to the D-xylose-containing nutrient medium of 0.1–1.5% D-glucose did not affect the enzyme synthesis in A. nicotianae, but suppressed it in Erwinia carotovora subsp. atroseptica (by 7% at the highest concentration) and Escherichia coli (by 63 and 75% at concentrations of 0.1 and 1.0%, respectively). The enzyme proteins produced by the bacteria exhibited the same substrate specificity and electrophoretic mobility (PAGE) as xylose isomerase A. nicotianae, although insignificant differences in the major physicochemical properties were noted.     

Selection of a mutant strain of Lipomyces kononenkoae with dextranase synthesis resistant to catabolite repression

A mutant strain of Lipomyces kononenkoae 2896-3 synthesizing dextranase but resistant to catabolite repression was obtained using N-nitroso-N-methylurea treatment. Enzyme biosynthesis in media with dextran and other carbon sources was then characterized. The capacity of the mutant to produce dextranase when grown on hydrolysed corn starch is demonstrated.     

Screening of glucose isomerase-producing microorganisms

The ability to convert D-glucose into D-fructose was found in 14 out of 74 species of actinomycetes and bacteria tested. High intracellular glucose isomerase activity was displayed by Arthrobacter sp. and actinomycetes Streptomyces viridobrunneus, Streptomyces sp. 1 and Streptomyces sp. 32. The first showed maximal glucose-converting potential when cultured in both glucose and xylose media, while glucose isomerase activity of Streptomyces species could be found solely in medium supplemented with xylose. The ketose enzymatically formed from D-glucose was identified as D-fructose.     

Selection of Penicillium funiculosum Strains with High Glucose Oxidase Activity

Metabolic inhibitors, riboflavin, and end products of glucose oxidation were shown to be effective for the selection ofPenicillium funiculosum mutant strains with a high glucose oxidase activity. The incidence of positive mutations was highest in clones resistant to sodium azide, riboflavin, and -D-glucono--lactone. Enzyme activity in Penicillium funiculosum mutants was studied in submerged culture. The level of glucose oxidase synthesis in seven cultures was 24–56% higher than that in the parent strain of Penicillium funiculosum NMM95.132.     

Influence of hypoxia and anoxia on endothelium-dependent dilatation response of rat's aorta exposed to low-intensity gamma irradiation

The study of isolated segments of aorta has shown that prolongated exposure of rats to gamma-radiation with 50 cGy dose (with a dose rate of 2.8 x 10(7) Gy/s) causes the decrease in endothelium-dependent dilatation responses to M-cholinoreceptors stimulation. During oxygenation the post-radiation changes are displayed within one month, and under functional loads, specifically, during perfusion by hypoxic and anoxic solutions--in more remote terms of the post-radiation period.     

Composition and biological activity of submerged mycelium of the xylotrophic basidiomycete Lentinus edodes

The composition of submerged mycelium of Lentinus edodes, grown in laboratory fermenters, has been studied. The mycelium contained 23-24% proteins, 8-9% lipids, up to 1800 mg% phenolic substances, and a significant amount of inorganic substances, including calcium and iron. The fungus produced up to 5.0% intracellular and 3.5-4.0 g/l extracellular polysaccharides. The submerged mycelium stimulated the development of humoral immune response elicited by sheep red blood cells.     

Biosynthesis of pectinlyases in Penicillium adametzii,P. citrinum and P. janthinellum

Pectinlyase complexes of Penicillium adametzii, P. citrinum and P. janthinellum occur as multiple molecular forms distinguished by their biosynthetic control. AMP is involved in derepression of pectinlyase formation.The authors are with the Institute of Microbiology, Belarus Academy of Sciences, Zhodinskaya 2, 220141, Minsk, Republic of Belarus.     

The effect of stimulation of the adrenergic receptors on the frequency depression of the temporal parameters of the action potential in the right atrium of rats]

At a stimulation rate of 1 Hz, activation of alpha-adrenoreceptors prolonged the AP duration at 10%, 50%, and 90% repolarisation at 10(-7), 10(-6) M in the rat isolated right atria, but shortened it at a higher concentration of 10(-5) M. The frequency-induced depression of the AP duration became more evident in cardiomyocytes stimulated by 10(-7), 10(-6) M and less obvious at 10(-5) M of alpha-adrenoagonist. Activation of alpha-adrenoreceptors by isoprenalin shortened the AP duration and enhanced the stimulation-rate-dependent changes in the atrial AP configuration.     

Effects of conditions ofPenicillium funiculosum G-15 cultivation on production of extracellular glucose oxidase

Effects of conditions ofPenicillium funiculosum G-15 cultivation on the production of extracellular glucose oxidase were studied. The data showed that surface and submerged methods of cultivation can be used for obtaining a glucose oxidizing enzyme. The optimum conditions for submerged cultivation (25°C., initial pH 5.0, and aeration of 3 1/1 per min) and surface cultivation (temperature 25°C and initial pH 4.0) providing the maximum levels of glucose oxidase synthesis were determined.