RESUMEN
Newcastle disease (NCD) is an important disease of poultry, directly affecting the livelihoods of poor farmers across developing countries. Research has identified promising innovations in NCD vaccine development and field trials among village poultry have been promising. However, NCD vaccination is not currently part of village poultry extension programmes in many developing countries. Understanding the preferences for, and relative importance of, different attributes of potential vaccination programmes to prevent NCD will be crucial in designing acceptable and sustainable prevention programmes. This research employed the discrete choice experiment approach to elicit farmers' preference for attributes of NCD vaccination programmes for village poultry in rural Ethiopia. The choice experiment survey was conducted on 450 smallholder farmers. The relative importance of attributes of NCD vaccines to farmers was estimated using a random parameter logit regression model. The preferred NCD vaccine programme had greater bird-level protection (i.e. greater capacity to reduce mortality should NCD occur in a flock), was delivered by animal health development agents, and could be administered via drinking water. Results from simulations on changes in attribute levels revealed that bird-level protection capacity and delivery of vaccine by animal heath extension affect farmers' preferences more than other attributes. These findings suggest that it is important to ensure NCD vaccine programmes offer reasonable capacity to protect against mortality. It also suggests the need to understand farmers' preferred vaccine delivery mechanisms and route of vaccine administration for a wider acceptance of vaccine.
Asunto(s)
Pollos , Conocimientos, Actitudes y Práctica en Salud , Programas de Inmunización/estadística & datos numéricos , Enfermedad de Newcastle/prevención & control , Enfermedades de las Aves de Corral/prevención & control , Vacunación/veterinaria , Vacunas Virales/administración & dosificación , Adulto , Animales , Etiopía , Agricultores , Femenino , Humanos , Masculino , Persona de Mediana Edad , Vacunación/psicologíaRESUMEN
The solvent resistance capacity of Pseudomonas putida S12 was applied by using the organism as a host for biocatalysis and through cloning and expressing solvent resistant pump genes into Escherichia coli. P. putida S12 expressing toluene ortho mononooxygenase (TOM-Green) was used for 1-naphthol production in a water-organic solvent biphasic system. Application of P. putida S12 improved 1-naphthol production per gram cell dry weight by approximately 42% compared to E. coli. Moreover, P. putida S12 enabled the use of a less expensive solvent, decanol, for 1-naphthol production. The solvent resistant pump (srpABC) genes of P. putida S12 were cloned into a solvent sensitive E. coli strain to transfer solvent tolerance. Recombinant strains bearing srpABC genes in either a low-copy number or a high-copy number plasmid grew in the presence of saturated concentration of toluene. Both of the recombinant strains were more tolerant to 1% v/v of toxic solvents, decanol and hexane, reaching similar cell density as the no-solvent control. Reverse-transcriptase analysis revealed that the srpABC genes were transcribed in engineered strains. The results demonstrate successful transfer of the proton-dependent solvent resistance mechanism and suggest that the engineered strain could serve as more robust biocatalysts in media with organic solvents.
Asunto(s)
Proteínas Bacterianas/genética , Escherichia coli/crecimiento & desarrollo , Oxigenasas de Función Mixta/metabolismo , Pseudomonas putida/fisiología , Solventes/metabolismo , Proteínas Bacterianas/metabolismo , Biocatálisis , Clonación Molecular , Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Oxigenasas de Función Mixta/genética , Naftoles/metabolismo , Pseudomonas putida/enzimología , Pseudomonas putida/genética , Tolueno/metabolismoRESUMEN
Whole-cell biocatalysis to oxidize naphthalene to 1-naphthol in liquid-liquid biphasic systems was performed. Escherichia coli expressing TOM-Green, a variant of toluene ortho-monooxygenase (TOM), was used for this oxidation. Three different solvents, dodecane, dioctyl phthalate, and lauryl acetate, were screened for biotransformations in biphasic media. Of the solvents tested, lauryl acetate gave the best results, producing 0.72 +/- 0.03 g/liter 1-naphthol with a productivity of 0.46 +/- 0.02 g/g (dry weight) cells after 48 h. The effects of the organic phase ratio and the naphthalene concentration in the organic phase were investigated. The highest 1-naphthol concentration (1.43 g/liter) and the highest 1-naphthol productivity (0.55 g/g [dry weight] cells) were achieved by optimization of the organic phase. The ability to recycle both free cells and cells immobilized in calcium alginate was tested. Both free and immobilized cells lost more than approximately 60% of their activity after the first run, which could be attributed to product toxicity. On a constant-volume basis, an eightfold improvement in 1-naphthol production was achieved using biphasic media compared to biotransformation in aqueous media.
Asunto(s)
Naftoles/metabolismo , Acetatos , Biotecnología , Biotransformación , Catálisis , Células Inmovilizadas , Ingeniería Química , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Escherichia coli/metabolismo , Oxigenasas de Función Mixta/genética , Oxigenasas de Función Mixta/metabolismo , Naftalenos/metabolismo , Naftalenos/toxicidad , Naftoles/toxicidad , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , SolventesRESUMEN
The selective oxidation of aryl substrates to chiral cis-1,2-dihydrodiols is an industrially important reaction for the production of intermediates that can be used to produce fine chemicals, pharmaceuticals, and many other bioactive natural products. More specifically, the oxidation of naphthalene to produce optically pure (+)-cis-(1R,2S)-1,2-napthalene dihydrodiol (NDHD) to be used as a chiral synthon for specialty chemicals has gained much interest. Escherichia coli JM109(DE3) pDTG141 expresses naphthalene dioxygenase which catalyzes this reaction. Poor substrate solubility and substrate toxicity are barriers to using the power of these enzymes in large-scale aqueous whole cell systems. A biphasic reaction system was chosen to overcome these barriers. The optimal biphasic conditions for E. coli JM109(DE3) pDTG141 were determined to be 20% dodecane as the organic solvent containing 40 g/L naphthalene. The productivity of the biotransformation using resting cells was 1.75 g-diol/g-cdw/h for the first 6 h with 20% organic phase, which was increased from 0.59 g-diol/g-cdw/h for growing cells with 40% organic phase. The biocatalytic activity was retained for at least 12 h. The biocatalyst could be recycled for at least four runs in both suspended and immobilized form. The stability of the 12 h recycle was improved by immobilization in calcium alginate beads. The process has been improved both environmentally and economically by reducing the amount of solvent used and by recycling the biocatalyst.