ABSTRACT
Synthesis of 3- and 4-hydroxybutyrate copolymer (3HB-CO-4HB), the most promising member of the biodegradable polyhydroxyalcanoate (PHA) family, has been studied. Cultivation conditions of naturally occurring strains of hydrogen-oxidizing bacteria Ralstonia eutropha B5786 and Cupriavidus eutrophus B10646 have been optimized to ensure efficient synthesis of the 3HB-CO-4HB copolymer. A set of highly pure samples of the 3HB-CO-4HB copolymer with 4HB content varying from 8.7 to 24.3 mol % has been obtained. Incorporation of 4-HB into the copolymer was shown to cause a more pronounced decrease in polymer crystallinity than the incorporation of 3-hydroxyvalerate or 3-hydroxyhexanoate; samples with a degree of crystallinity below 30% have been obtained. The weight average molecular mass of the 3HB-CO-4HB copolymers was shown to be independent on the monomer ratio and to vary broadly (from 540 to 1110 kDa).
Subject(s)
Cupriavidus necator/growth & development , Cupriavidus necator/metabolism , Hydrogen/metabolism , Hydroxybutyrates/metabolism , Polyesters/metabolism , Cell Culture Techniques , Crystallography , Culture Media/chemistry , Cupriavidus necator/genetics , Hydroxybutyrates/chemistry , Oxidation-Reduction , Polyesters/chemistryABSTRACT
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.
Subject(s)
Bacteria/isolation & purification , Ecosystem , Fresh Water/microbiology , Polymers/metabolism , Bacteria/classification , Bacteria/genetics , DNA Primers , DNA, Bacterial/analysis , DNA, Bacterial/genetics , Electrophoresis, Polyacrylamide Gel , Fresh Water/analysis , Polymerase Chain Reaction , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , Seasons , Siberia , Species Specificity , TemperatureSubject(s)
Biopolymers , Manufactured Materials , Plastics/chemistry , Biodegradation, Environmental , Environment , Kinetics , Russia , Water SupplyABSTRACT
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.
Subject(s)
Cupriavidus necator/enzymology , Hydroxybutyrates/metabolism , Acetyl-CoA C-Acyltransferase/chemistry , Acetyl-CoA C-Acyltransferase/metabolism , Acyltransferases/chemistry , Acyltransferases/metabolism , Alcohol Oxidoreductases/chemistry , Alcohol Oxidoreductases/metabolism , Carboxylic Ester Hydrolases/chemistry , Carboxylic Ester Hydrolases/metabolism , Culture Media , Cupriavidus necator/growth & development , Hydroxybutyrate Dehydrogenase/chemistry , Hydroxybutyrate Dehydrogenase/metabolism , PolymersABSTRACT
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.
Subject(s)
Chlorophyta/metabolism , Lipids/biosynthesis , Chlorophyta/growth & development , Fatty Acids/analysis , Lipids/chemistry , Temperature , Triglycerides/biosynthesis , Triglycerides/chemistryABSTRACT
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.
