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Biomedical subjects

G A Bonartseva

Publications and source records attributed to G A Bonartseva.

12 recordsLinked to original sources
PubMedDate not supplied

Aerobic and anaerobic microbial degradation of poly-beta-hydroxybutyrate produced by Azotobacter chroococcum.

Food industry wastewater served as a carbon source for the synthesis of poly-beta-hydroxybutyrate (PHB) by Azotobacter chroococcum. The content of polymer in bacterial cells grown on the raw materials reached 75%. PHB films were degraded under aerobic, microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site. Changes in molecular mass, crystallinity, and mechanical properties of PHB were studied. Anaerobic degradation was accompanied by acetate formation, which was the main intermediate utilized by denitrifying bacteria or methanogenic archaea. On a decrease in temperature from 20 to 5 degrees C in the presence of nitrate, the rate of PHB degradation was 7.3 times lower. Under anaerobic conditions and in the absence of nitrate, no PHB degradation was observed, even at 11 degrees C. The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic sludge degraded PHB films for a short time (3-7 d). The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri. The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time during biodegradation.

Aerobiosis↗
PubMedDate not supplied

[Role of leguminous plants in effective symniosis with nodule bacteria].

Experiments were conducted with five clover varieties and six lucerne varieties infected with their specific strains of nodule bacteria with a high or low activity. The role of plants in active symbiosis with nodule bacteria was established. The nitrogen fixing activity of nodule bacteria varied within a wide range depending on the plant variety. Not only the activity of the strain, but the variety of the plant too, should be taken into account for industrial purposes.

Medicago sativa↗
PubMedDate not supplied

[Oxidative phosphorylation in Propionibacterium].

Oxidative phosphorylation during electron transport in the respiratory chain was found in two propionic bacteria, P. shermanii and P. petersonii. Its effectiveness, with oxygen as the terminal acceptor of electrons, was higher in P. petersonii, a more aerobic culture, than in P. shermanii. Oxidative phosphorylation with the participation of the electron transport chain was not found in P. petersonii in the absence of oxygen. Oxidative phosphorylation can take place together with the reactions of propionic fermentation in P. shermanii upon a small rearrangement of the respiration chain (if fumarate reductase is substituted for cytochrome oxidase).

Aerobiosis↗
PubMedDate not supplied

[The biodegradation of poly-beta-hydroxybutyrate (PHB) by a model soil community: the effect of cultivation conditions on the degradation rate and the physicochemical characteristics of PHB].

The biodegradation of films made of poly-beta-hydroxybutyrate (PHB) with a molecular mass of 1500 kDa was studied using a model soil community in the presence and absence of nitrate and at different concentrations of oxygen in the gas phase. The biodegradation of PHB was investigated with respect to changes in its molecular mass, crystallinity, and some mechanical properties.

Biodegradation, Environmental↗
PubMedDate not supplied

[New poly-(3-hydroxybutyrate)-based systems for controlled release of dipyridamole and indomethacin].

New poly-(3-hydroxybutyrate)-based systems for controlled release of anti-inflammatory and antithrombogenic drugs have been studied. The release occurs via two mechanisms (diffusion and degradation) operating simultaneously. Dipyridamole and indomethacin diffusion processes determine the rate of the release at the early stages of the contact of the system with the environment (the first 6-8 days). The coefficient of the release diffusion of a drug depends on its nature, the thickness of the poly-(3-hydroxybutyrate) films containing the drug, the concentrations of dipyridamole and indomethacin, and the molecular weight of the poly-(3-hydroxybutyrate). The results obtained are critical for developing systems of release of diverse drugs, thus, enabling the attainment of the requisite physiological effects on tissues and organs of humans.

Azotobacter↗
PubMedDate not supplied

[Preparation of biodegradable porous films for use as wound coverings].

We studied the preparation of polymeric films formed from solutions of poly-3-hydroxybutyrate and poly-epsilon-caprolactone in chloroform and methylene chloride. A morphological study of film chips (electron microscopy) showed that solvent evaporation results in the formation of a heterogeneous structure with interpenetrating pores (1-20 microm). We proposed a new method for introducing the proteolytic enzyme and the aminopolysaccharide chitosan into the composition of polyester films. Composite films possessed necrolytic activity and were characterized by increased hydrophilicity. Properties of enzyme-containing films from a mixture of polymers (proteolytic activity, porous structure, and increased hydrophilicity) account for their use in the preparation of biodegradable wound coverings.

Bandages↗
PubMedDate not supplied

[Determination of the nitrogen-fixing activity of Rhizobium japonicum under sterile microvegetative conditions].

The nitrogen fixing activity of Rhizobium japonicum in symbiosis with soya grown in the sterile microvegetative conditions at an air humidity of 70%, at a temperature of 20 degrees C and a length of light day of 16 hours was assayed using the acetylene technique. The plants were cultivated in phytotron in glass tubes (245 cm3) illuminated with xenon lamps. This technique can be used, apparently, to determine the nitrogen fixing activity of other legumes and cereals.

Humidity↗
PubMedDate not supplied

[Nitrogenase activity of Rhizobium meliloti and Rhizobium vigna in a root tisse culture of leguminous and nonleguminous plants].

As was shown using the acetylene technique, the nitrogenase activity of Rhizobium meliloti and Rhizobium vigna increased when they were cultivated with the root tissue cultures of legumes (lucerne, sweetclover) and non-legumes (tobacco, glasswort, carrot), particularly in the case of the former. The maximum activity of nitrogenase was found in R. meliloti. The tissue cultures of legumes had no effect on the growth of Rhizobium whereas the tissues of non-legumes stimulated their biomass accumulation though the activity of nitrogenase in both Rhizobium cultures was low in this case. Therefore, the metabolites of legumes produced a specific action on the nitrogenase of nodule bacteria.

Culture Media↗
PubMedDate not supplied

Action of metabolites of isolated plant tissues on the nitrogenase activity of Rhizobium vigna and Rhizobium meliloti.

The dependence of the nitrogenase activity of Rhizobium meliloti on the strain peculiarities of the cultures, the composition of the media used, and the metabolites of legume tissue cultures was demonstrated by the acetylene method. The nitrogenase activity is significantly higher in R. vigna than in R. meliloti, under the same experimental conditions. Enrichment of the Murashige-Skoog medium with arabinose (25 mM), succinate (25 mM), glutamine (2 mM nitrogen), and yeast extract (0.1%) substantially stimulated the nitrogenase activity of a pure culture of R. vigna. The maximum nitrogenase activity on this medium was noted when metabolites of sweet clover tissue were introduced.

Ethylenes↗