RESUMEN
The gene phaPAh, encoding the protein phasin that is associated with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) granule of Aeromonas hydrophila 4AK4, was cloned and characterized. Recombinant strains harboring additional copies of the phasin gene (phaPAh) and the polyhydroxyalkanoate (PHA) synthase gene (phaCAh) accumulated PHBHHx copolyesters consisting of 21 mol% 3-hydroxyhexanoate (3HHx) as compared to 14 mol% 3HHx produced by wild type strain. The molecular weight of PHBHHx produced by the above recombinants was lower than that obtained from the wild type strain grown under similar conditions. Over-expression of phaPAh led to the production of more PHA granules but with reduced sizes. SDS-PAGE showed that PhaPAh was the predominant protein present in the PHBHHx granules. The RT-PCR results suggested that phasin PhaPAh, regulated phaCAh gene at the transcription level. Gene PhaPWe from Wautersia eutropha (formerly Ralstonia eutropha; encoding a 20 kDa protein with low amino acid homology to the A. hydrophila 13 kDa protein) cloned into A. hydrophila 4AK4 exhibited similar effects on PHBHHx production and PHBHHx composition. These data suggest that the phasins could represent a protein family possessing similar functions but different structures.
Asunto(s)
Aeromonas hydrophila/genética , Aeromonas hydrophila/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Genes Bacterianos , Poliésteres/metabolismo , Ácido 3-Hidroxibutírico/metabolismo , Aeromonas hydrophila/crecimiento & desarrollo , Aeromonas hydrophila/ultraestructura , Secuencia de Bases , Caproatos/metabolismo , Clonación Molecular , ADN Bacteriano/genética , Expresión Génica , Microscopía Electrónica , Reacción en Cadena de la PolimerasaRESUMEN
Ni-doped TiO2 film catalysts were prepared by a plasma electrolytic oxidation (PEO) method and were mainly characterized by means of SEM, EDS, XRD, XPS, and DRS, respectively. The effects of Ni doping on the structure, composition and optical absorption property of the film catalysts were investigated along with their inherent relationships. The results show that the film catalyst is composed of anatase and rutile TiO2 with microporous structure. Doping Ni changes the phase composition and the lattice parameters (interplanar crystal spacing and cell volume) of the films. The optical absorption range of TiO2 film gradually expands and shifts to the red with increasing dosages. Both direct and indirect transition band gaps of the TiO2 films are deduced consequently. Moreover, the photocatalytic activity of the film catalysts for splitting Na2S+Na2SO3 solution into H2 is enhanced by doping with an appropriate amount of Ni. The as-prepared TiO2 film catalyst doping with 10 g/L of Ni(Ac)2 presents the highest photocatalytic reducing activity.