Physiological–biochemical properties and the ability to synthesize polyhydroxyalkanoates of the glucose-utilizing strain of the hydrogen bacterium Ralstonia eutropha B8562

Physiological-biochemical, genetic, and cultural properties of the glucose-utilizing mutant strain Ralstonia eutropha B8562 have been compared with those of its parent strain R. eutropha B5786. It has been shown that growth characteristics of the strain cultured on glucose as the sole carbon and energy source are comparable with those of the parent strain. Strain B8562 is characterized by high polyhydroxyalkanoate (PHA) yields on different carbon sources (CO(2), fructose, and glucose). PHA accumulation in the strain batch cultured on glucose under nitrogen deficiency reaches 90 %. The major monomer in the PHA is beta-hydroxybutyric acid (more than 99 mol %); the identified minor components are beta-hydroxyvaleric acid (0.25-0.72 mol %) and beta-hydroxyhexanoic acid (0.08-1.5 mol %). The strain is a promising PHA producer on available sugar-containing media with glucose.

[Degradation of polyhydroxyalkanoates and the composition of microbial destructors under natural conditions]

The degradation dynamics of polyhydroxyalkanoates of different composition has been studied in an eutrophic storage reservoir for two seasons. It has been shown that the biodegradation of polymers under natural conditions depends not only on their structure and physicochemical properties but also, to a great extent, on a complex of weather-climatic conditions affecting the state of the reservoir ecosystem. The molecular genetic analysis of 16S rRNA has revealed bacterial species (clones) probably involved in the degradation of polyhydroxyalkanoates in a model storage reservoir.

[Physiological and biochemical characteristics and capacity for polyhydroxyalkanoates synthesis in a glucose-utilizing strain of hydrogen-oxidizing bacteria, Ralstonia eutropha B8562]

The physiological, biochemical, genetic, and cultural characteristics of the glucose-utilizing mutant strain Ralstonia eutropha B8562 were investigated in comparison with the parent strain R. eutropha B5786. The morphological, cultural, and biochemical characteristics of strain R. eutropha B8562 were similar to those of strain R. eutropha B5786. Genetic analysis revealed differences between the 16S rRNA gene sequences of these strains. The growth characteristics of the mutant using glucose as the sole carbon and energy source were comparable with those of the parent strain grown on fructose. Strain B8562 was characterized by high yields of polyhydroxyalkanoate (PHA) from different carbon sources (CO2, fructose, and glucose). In batch culture with glucose under nitrogen limitation, PHA accumulation reached 90% of dry weight. In PHA, beta-hydroxybutyrate was predominant (over 99 mol %); beta-hydroxyvalerate (0.25-0.72 mol %) and beta-hydroxyhexanoate (0.008-1.5 mol %) were present as minor components. The strain has prospects as a PHA producer on glucose-containing media.

[The synthesis of hydroxybutyrate and hydroxyvalerate copolymers by the bacterium Ralstonia eutropha]

The paper deals with the study of the synthesis of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) copolymers by the bacterium Ralstonia eutropha B-5786 grown under different carbon nutrition conditions (growth on carbon dioxide, fructose, and CO2-valerate and fructose-valerate mixtures). The parameters to be analyzed included the yield of biomass, the yield, synthesis rate, and composition of copolymers, the activity of the key enzymes of polyhydroxyalkanoate (PHA) synthesis (beta-ketothiolase, acetoacetyl-CoA reductase, and PHA synthase), the maximum tolerable concentration of valerate to the bacterium, and the conditions that govern the incorporation of hydroxyvalerate to copolymers. This allowed the relationship between cultivation conditions and the proportion of monomers in the copolymers to be deduced. We were able to synthesize a range of 3HB/3HV copolymers and found that the thermal characteristics and the degree of crystallinity of these copolymers depend on the molar fraction of 3HV.

[Biodegradable polyhydroxyalkanoates as carriers for antitumor agents]

The possible use of biodegradable polyethers of microbial origin (polyhydroxyalkanoates) as matrices for deposition of daunorubicin (rubomycin), an antitumor anthracycline, was studied. The tablet dosage form of various rubomycin load (from 1 to 60% w/w) was prepared by cold compaction under pressure. The in vitro kinetics of the rubomycin release from the polymer matrix was investigated. It was shown that the rubomycin release to the medium resulted from the drug solution and diffusion within various periods, from tens hours to several weeks and months depending on the load. When the rubomycin load was under 20% w/w the drug release was prolonged and directly proportional to the observation time. When the rubomycin concentration was under 5%, the drug release kinetics corresponded to the type of the zero order reaction with prolonged release without sharp efflux at the initial stage of the observation. The findings showed that the polyhydroxyalkanoates were applicable as matrices for deposition of rubomycin and preparation of drugs with prolonged action.

[Physicochemical properties of two-component polyhydroxyalkanoates based on 3-hydroxybutyrate and 3-hydroxyvalerate]

A series of two-component polyhydroxyalkanoates consisting of hydroxybutyrate and hydroxyvalerate monomer at different ratios were synthesized using the bacterium Ralstonia eutropha B5786. The properties of polyhydroxyalkanoates were compared with those of the homopolymer of hydroxybutyric acid by X-ray structure analysis, IR spectroscopy, differential scanning calorimetry, and viscosimetry. With an increase in the molar fraction of hydroxyvalerate, an equalization of the ratio of the crystalline and amorphous phases in the copolymer was observed. The degree of crystallinity of the polymer decreased from 70-80 to 45-50%; in the range of an increase in the hydroxyvalerate molar fraction from several to 25-30 mol%, the dependence was linear. The temperature characteristics, the melting temperature (T(m)), and the degradation temperature (T(d)) were lower in polyhydroxyalkanoates than in polyhydroxybutyrate, for which T(m) and T(d) were 168-170 and 260-265 degrees C, respectively. In the copolymer, as the molar fraction of hydroxyvalerate grew, both parameters decreased. In the range of variation of monomer ratio studied, they decreased to 150-160 and 200-220 degrees C, respectively. No distinct correlation between the composition of the polymer and its molecular mass was found.

A comparative investigation of biodegradable polyhydroxyalkanoate films as matrices for in vitro cell cultures

The paper describes the production and investigation of flexible films made of high-purity polyhydroxyalkanoates (PHAs)--polyhydroxybutyrate [poly-(3HB)] and poly-3-hydroxybutyrate-co-poly-3-hydroxyvalerate [poly(3HB-co-3HV)], containing 4-30 mol % hydroxyvalerate. Poly(3HB-co-3HV) films have a more porous structure than poly-(3HB) films, which are more compact, but their surface properties, such as wettability and surface and interface energies, are the same. Sterilisation of the PHA films by conventional methods (heat treatment and gamma-irradiation) did not impair their strength. Cells cultured on PHA films exhibited high levels of cell adhesion. Cell morphology, protein synthesis and DNA synthesis were estimated by extent of 3H-thymidine incorporation into the animal cell cultures of various origins (fibroblasts, endothelium cells, and isolated hepatocytes) in direct contact with PHAs. The investigation showed that this material can be used to make matrices for in vitro proliferous cells. The investigated properties of poly-(3HB) and poly(3HB-co-3HV) films proved to be fundamentally similar.

Tissue response to the implantation of biodegradable polyhydroxyalkanoate sutures

Polyhydroxyalkanoate (PHA) sutures were implanted to test animals intramuscularly, and tissue reaction was investigated and compared with the reaction to silk and catgut. Tested monofilament sutures made of PHAs of two types--polyhydroxybutyrate (PHB) and a copolymer of hydroxybutyrate and hydroxyvalerate (PHV)--featured the strength necessary for the healing of muscle-fascial wounds. The reaction of tissues to polymeric implants was similar to their reaction to silk and was less pronounced than the reaction to catgut; it was expressed in a transient post-traumatic inflammation (up to four weeks) and the formation of a fibrous capsule less than 200 microm thick, which became as thin as 40-60 microm after 16 weeks, in the course of reverse development. Macrophages and foreign-body giant cells with a high activity of acid phosphatase were actively involved in this process. PHB and PHB/PHV sutures implanted intramuscularly for an extended period (up to one year) did not cause any acute vascular reaction at the site of implantation or any adverse events, such as suppurative inflammation, necrosis, calcification of the fibrous capsule or malignant tumor formation. No statistically significant differences were revealed in the tissue response to polymer sutures of the two types. Capsules around silk and catgut sutures did not become significantly thinner.

[Study of Ralstonia eutropha culture producing polyhydroxyalkanoates on products of coal processing]

Kinetic indices of growth, polyhydroxyalkanoate (PHA) accumulation, and gas exchange have been studied in a culture of the carbon monoxide-resistant hydrogen strain Ralstonia eutropha B-5786 grown on a gaseous substrate (GS) obtained by lignite gasification. The GS was shown to be suitable for PHA production. To increase the degree of GS consumption, various modes of gas supply to the culture were tested. Based on the results, an algorithm was developed for calculating and controlling gas-exchange parameters in the PHA-accumulating culture of Ralstonia eutropha, grown on a new GS allowing high polymer yields (up to 75%) and degrees of the substrate utilization (up to 90%).

[Dynamics of activity of the key enzymes of polyhydroxyalkanoate metabolism in Ralstonia eutropha]

The dynamics of accumulation of polyhydroxybutyrate (PHB) and the activities of the key enzymes of PHB metabolism (beta-ketothiolase, acetoacetyl-CoA reductase, PHA synthase, D-hydroxybutyrate dehydrogenase, and PHA depolymerase) in the hydrogen bacterium Ralstonia eutropha B5786 were studied under various conditions of carbon nutrition and substrate availability. The highest activities of beta-ketothiolase, acetoacetyl-CoA reductase, and PHA synthase were recorded at the stage of acceleration of PHB synthesis. The activities of enzymes catalyzing PHB depolymerization (PHB depolymerase and D-hydroxybutyrate dehydrogenase) were low, being expressed only at stimulated endogenous PHB degradation. The change of carbon source (CO2 or fructose) did not cause any marked changes in the time course of enzyme activity.

[Kinetic parameters of a culture of the hydrogen-oxidizing Ralstonia eutropha, grown under the regimen of biosynthesis of polyhydroxybutyrate]

Kinetic parameters of a culture of the hydrogen-oxidizing bacterium Ralstonia eutropha, grown on a gas substrate under the conditions favoring autotrophic biosynthesis of polyhydroxybutyrate, were studied. The following parameters, making it possible to control and optimize the process in industrial situations, were determined: specific rate of substrate consumption, physical properties of culture medium, and coefficients of heat emission and mass transfer.

Production of purified polyhydroxyalkanoates (PHAs) for applications in contact with blood

Samples of olyhydroxyalkanoates (PHAs), polyhydroxybutyrate (PHB) and copolymers poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with 4 and 18 mol% hydroxyvalerate, synthesized by the bacteria Ralstonia eutropha B5786, were investigated. PHA films in contact with blood did not activate the hemostasis system at the level of cell response, but they did activate the coagulation system and the complement reaction. To detect biologically-active components in the PHAs, a detailed analysis of the composition of the polymers was conducted. Gas chromatography-mass spectrometry revealed long-chain fatty acids (FAs) in the tested PHAs. Their total concentration in the polymer ranged from tenths of mol% to 2-3 mol%, depending on the purification method. C16:0 constituted the largest proportion, up to 70%. Of the long-chain hydroxy acids, only beta-OH-C14:0 was detected and it did not exceed 0.06 mol%. The analysis of the hemocompatibility properties of the PHAs purified by a specialized procedure, including the quantitative and morphological estimation of platelets adherent to the surface of polymer films, the plasma recalcification time and complement activation studies, indicated that PHB and PHBV can be used in contact with blood. It has been found out that the lipopolysaccharides of bacteria producing PHAs, which contain mostly long-chain hydroxy acids, can be the factor activating the hemostasis systems. Thus, the technology of PHA purification must satisfy rather stringent specific requirements.

[Tissue reactions to biodegradable suture materials from polyoxyalkanoates]

The paper presents data on the materials, methods, and results of a study of tissue responses in the postoperative period to implanted suture threads made of the polymer fatty acid derivatives (polyoxyalkanoates). These suture threads have been shown to have the required strength and meet a number of other requirements for currently available materials.

[Biological properties of polyoxyalkanoates in chronic experiments in vivo]

Chronic experiments on mature Wistar rats studied the biological properties of suture threads from two types of polyoxyalkanoates (POA), such as polyoxybutyrate (POB) and the copolymer of POB and polyoxyvalerate (POV) (POB/POV) as compared to the conventional surgical material (silk and catgut). The physiological and biochemical parameters that reflect the status of the animals, including their behaviour, height and development, the weight of the body and viscera, the morphology of peripheral blood, the biochemical parameters of blood, the activity of some enzymes, as well as histological findings of the viscera, and lymphoid tissue responses were assessed. POA was found to produce no negative effect on the physiological, biochemical, and functional characteristics of the animals irrespective of the duration of contact with the internal medium of the body and of the chemical composition of a material.

[The effect of temperature on the lipid composition of Botryococcus]

The lipid composition of the green alga Botryococcus was studied at three different cultivation temperatures: suboptimal, optimal, and supraoptimal. Cultivation at the supraoptimal temperature was found to considerably inhibit the synthesis of nearly all intracellular lipids, except for triacylglycerides, and to influence their fatty acid composition. In particular, the content of trienoic fatty acids was significantly lower at the supraoptimal than at the optimal cultivation temperature. At the same time, the fatty acid composition of the extracellular lipids of the alga virtually did not depend on cultivation temperature.

Autotrophic synthesis of polyhydroxyalkanoates by the bacteria Ralstonia eutropha in the presence of carbon monoxide

It has been found that the carbon monoxide (CO)-resistant strain of the hydrogen bacteria Ralstonia eutropha B5786 is able to synthesise polyhydroxyalkanoates (PHAs) in the presence of CO under autotrophic conditions. This strain, grown on model gas mixtures containing 5-25% CO (v/v), accumulates up to 70-75% (of absolutely dry matter) PHA, without significant variation in the yield coefficient on hydrogen. No suppression of the activities of the key enzymes of PHA synthesis ( beta-ketothiolase, acetoacetyl-CoA-reductase, butyrate dehydrogenase and poly-3-hydroxybutyrate synthase) was recorded. The PHA synthesised is a co-polymer containing mostly beta-hydroxybutyrate (more than 99 mol%) with trace amounts of beta-hydroxyvalerate. The investigated properties of the polymer (molecular weight, crystallinity, temperature characteristics) do not differ from those of the polymer synthesised on electrolytic hydrogen.

[Autotrophic synthesis of polyalkanoates by Alcaligenes eutrophus in presence of carbon monoxide]

The CO-resistant strain B5786 of the hydrogen-oxidizing bacterium Alcaligenes eutrophus was found to be able to synthesize polyhydroxyalkanoates (PHAs) under the conditions of growth limitation by nitrogen deficiency (the factor that promotes PHA synthesis) and growth inhibition by carbon monoxide. The gas mixtures that contained from 5 to 20 vol% CO did not inhibit the key enzymes of PHA synthesis--beta-ketothiolase, acetoacetyl-CoA reductase, hydroxybutyrate dehydrogenase, and PHA synthase. In the presence of CO, cells accumulated up to 70-75 wt% PHA (with respect to the dry biomass) without any noticeable increase in the consumption of the gas substrate. Chromatographic-mass spectrometric analysis showed that the PHA synthesized by A. eutrophus is a copolymer containing more than 99 mol% beta-hydroxybutyrate and trace amounts of beta-hydroxyvalerate. The PHA synthesized under the conditions described did not differ from that synthesized by A. eutrophus cells from electrolytic hydrogen.

[Lipids from the green algae Botryococcus during staged growth in batch mode]

The lipid fraction of the green alga Botryococcus cultured in a batch mode was found to contain polar lipids (more than 50% of the total lipids), di- and triacylglycerides, steroids and their esters, free fatty acids, and hydrocarbons. In senescent culture, the content of polar lipids somewhat decreased and that of triacylglycerides increased by more than four times. The content of hydrocarbons in the algal biomass did not exceed 0.9% and depended little on the culture age. Intracellular lipids contained saturated and unsaturated (mono-, di-, and trienoic) fatty acids. The maximum content of C16:3 and alpha-C18:3 fatty acids (up to 35% of the total fatty acids) was detected in the phase of active growth. The extracellular and intracellular lipids of the alga differed in the proportion of particular lipids and in the fatty acid pattern.