RESUMO
Fertilizers contain essential nutrients for agricultural growth and development. However, most nitrogen fertilizers are substances with high solubility of ions and are very susceptible to leaching and volatilization. To minimize these losses, an alternative is the creation of a physical barrier around granules. One way is to coat granules with polymers. In the present work urea granules were coated with polyhydroxybutyrate and ethyl cellulose in various conditions in the presence of emulsifiers. The original granules and the final products were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetry, to evaluate the surface morphology, the interaction between the granules and the coating, and the rates of mass change. The rates of urea release in distilled water were measured with a commercial enzyme kit. It is shown that those polymers are effective for coating of granules, leading to reduction of rates of urea dissolution in water.
Assuntos
Celulose/análogos & derivados , Composição de Medicamentos/métodos , Fertilizantes/análise , Hidroxibutiratos/química , Polímeros/química , Ureia/química , Celulose/química , Cinética , SolubilidadeRESUMO
The proper determination of experimental errors in bioprocesses can be very important because experimental errors can exert a major impact on the analysis of experimental results. Despite this, the effect of experimental errors on the analysis of bioprocess data has been largely overlooked in the literature. For this reason, we performed detailed statistical analyses of experimental errors obtained during the production of lactobionic acid and sorbitol in a system utilizing as catalyst the GFOR (glucose-fructose oxidoreductase) enzyme from permeabilized cells of the bacteria Zymomonas mobilis. The magnitude of the experimental errors thus obtained were then correlated with the process operation conditions and with the composition of the culture media used for bacterial growth. It is shown that experimental errors can depend very significantly on the operation conditions and affect the interpretation of available experimental data. More specifically, in this study, experimental errors depended on the nutritional supplements added to the cultivation medium, the inoculation process, and the reaction time, which may be of fundamental importance for actual process development. The results obtained also indicate, for the first time, that GFOR activity can be affected by the composition of the medium in which cells are cultivated.
Assuntos
Dissacarídeos/biossíntese , Oxirredutases/metabolismo , Sorbitol/metabolismo , Zymomonas/enzimologia , Meios de Cultura , Zymomonas/crescimento & desenvolvimentoRESUMO
The structural stability of metmyoglobin in organic solvents and cosolvents was investigated aiming the choice of a suitable medium to perform its dissolution with maintenance of the native folding. The spectroscopic behavior of metmyoglobin solution in UV-Visible and circular dichroism was used to evaluate the solubility and the secondary structure. The results were dependable of the chemical structure of the organic compounds, their polarity and content, in the case of cosolvents. Protic solvents showed better ability than the aprotic ones for the biomolecule dissolution, since they are able to establish hydrogen bonds. Solvents with high polarity usually damage the secondary structure of the protein. Myoglobin was dissolved in pure methanol, ethylene glycol and glycerol. The secondary structure was retained in some extent. The controlled addition of sodium dodecyl sulfate to myoglobin aqueous solution changed the surface moiety of the protein. The complex was extracted to hexane with efficiency of 77%.
Assuntos
Metamioglobina/química , Compostos Orgânicos/química , Conformação Proteica , Estabilidade Proteica , Estrutura Secundária de Proteína , Solventes/químicaRESUMO
The last step of the production of four phthalimide-derived acids, designed to act as antiasthma drugs, was performed by enzymatic hydrolysis of the respective methyl or ethyl esters. The esters 4-ethyl-[2-(1,3-dioxo-1,3-dihydro- 2-isoindoylyl)]-phenoxyacetic methyl ester (PHT-MET), 4-ethyl-[2- (1,3-dioxo-1,3-dihydro-2-isoindoylyl)]-phenoxyacetic ethyl ester, 4-(1, 3-dioxo-1,3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester, and 2-(1,3-dioxo-1, 3-dihydro-2-isoindoylyl)-phenoxyacetic ethyl ester were hydrolyzed by immobilized lipase. The enzymatic reaction could be used only to produce the desired 4-substituted compounds. The best result that was found to hydrolysis of PHT-MET, and, therefore, that ester was selected for optimization experiments in a three-phase system. Reactions were performed with solid biocatalyst (Lipozyme RM IM), organic solvent phase (ethyl acetate), and aqueous phase (saturated Na2CO3 solution). To optimize the reaction conditions, an experimental design optimization procedure was used. The variables studied were the amount of enzyme, the temperature, and the volume of the aqueous solution. Time course experiments were then performed for different initial enzyme concentrations (0.5, 0.9, and 1.4 UH/mL of solvent). The optimized reaction conditions found were 20 mg of Lipozyme (0.9 UH/mL solvent) and 5.0 mL of Na2CO3(sat) at 40 degrees C for 6 h.