RESUMEN
In this study, we investigated the ability of Pseudomonas aeruginosa ATCC 27853 to grow and synthesize poly(3-hydroxyalkanoates) (PHAs) from saturated fatty acids with an even number of carbon atoms, from eight to 22, and from oleic acid. In a non-limiting medium, all carbon sources but docosanoic acid supported cell growth and PHA production, with eicosanoic acid giving the highest yield. In magnesium-limiting conditions, higher yields were obtained from sources with up to 16 carbon atoms. Composition was estimated by gas chromatography of methanolyzed samples and (13)C nuclear magnetic resonance. The 3-hydroxyalkanoate units extended from hexanoate to tetradecanoate or tetradecenoate, with octanoate and decanoate as the predominant components. Weight average molecular weights ranged from 78,000 to 316,000. Fast atom bombardment mass spectrometry of partially pyrolyzed samples, coupled to statistical analysis, showed that these PHAs are random copolymers.
Asunto(s)
Poliésteres/química , Poliésteres/metabolismo , Pseudomonas aeruginosa/metabolismo , Cromatografía de Gases , Ácidos Grasos/metabolismo , Sustancias Macromoleculares , Espectroscopía de Resonancia Magnética , Estructura Molecular , Peso Molecular , Pseudomonas aeruginosa/química , Espectrometría de Masa Bombardeada por Átomos VelocesRESUMEN
The sequence distributions of two microbial copolyesters obtained by fermentation of Rhodospirillum rubrum, grown with 3-hydroxyhexanoic or 3-hydroxyheptanoic acids, were determined by analyzing the oligomers prepared by partial pyrolysis or partial methanolysis of these copolyesters using fast atom bombardment mass spectrometry (FAB-MS). Oligomers up to pentamers were identified in the case of partial pyrolysis and up to tetradecamers in the case of partial methanolysis. The comparison between the experimental and calculated peak intensities of FAB mass spectra allows the calculation of compositions and sequence distributions, which in these copolyesters follow Bernoullian statistics, indicating that they are random terpolyesters.
Asunto(s)
Biopolímeros/biosíntesis , Biopolímeros/química , Caproatos/metabolismo , Rhodospirillum rubrum/química , Rhodospirillum rubrum/metabolismo , Ácidos Heptanoicos/metabolismo , Espectroscopía de Resonancia Magnética , Estructura Molecular , Espectrometría de Masa Bombardeada por Átomos VelocesRESUMEN
The sequence distributions of poly(beta-hydroxyalkanoate) copolymers were determined by analyzing oligomers obtained by the pyrolysis direct-chemical-ionization (DCI) mass spectrometry technique. Oligomers up to nonamers were identified and the comparison between the experimental and calculated peak intensities makes it possible to calculate repeating unit compositions and sequence distributions. Comparisons with other earlier methods are given.