Membrane adsorber for endotoxin removal

A superfície de membranas planas de nylon foi modificada utilizando-se bisoxirano como espaçador e poli(álcool vinílico) para recobrimento das membranas. O aminoácido histidina foi utilizado como ligante para endotoxinas, visando à sua aplicação na remoção de endotoxinas a partir de soluções aquosas. São discutidas as etapas de caracterização do adsorvedor com membranas, análise do procedimento de despirogenização e avaliação da eficiência de remoção em modo estático. A densidade de ligantes nas membranas foi em torno de 7 mg/g membrana (massa seca), permitindo uma remoção de endotoxinas de até 65%. O desempenho das membranas preparadas com nylon e recobertas com poli(álcool vinílico) contendo histidina como ligante foi superior ao de outros adsorvedores com membranas descritos na literatura. A ausência de adsorção de endotoxinas em membranas sem histidina confirma que a remoção das endotoxinas deve-se exclusivamente à presença do ligante na superfície da membrana. As membranas modificadas mostraram-se bastante estáveis, exibindo um tempo de vida superior a 30 dias.The surface of flat-sheet nylon membranes was modified using bisoxirane as the spacer and polyvinyl alcohol as the coating polymer. The amino acid histidine was explored as a ligand for endotoxins, aiming at its application for endotoxin removal from aqueous solutions. Characterization of the membrane adsorber, analysis of the depyrogenation procedures and the evaluation of endotoxin removal efficiency in static mode are discussed. Ligand density of the membranes was around 7 mg/g dry membrane, allowing removal of up to 65% of the endotoxins. The performance of the membrane adsorber prepared using nylon coated with polyvinyl alcohol and containing histidine as the ligand proved superior to other membrane adsorbers reported in the literature. The lack of endotoxin adsorption on nylon membranes without histidine confirmed that endotoxin removal was due to the presence of the ligand at the membrane surface. Modified membranes were highly stable, exhibiting a lifespan of approximately thirty months

Membrane adsorber for endotoxin removal

ABSTRACT The surface of flat-sheet nylon membranes was modified using bisoxirane as the spacer and polyvinyl alcohol as the coating polymer. The amino acid histidine was explored as a ligand for endotoxins, aiming at its application for endotoxin removal from aqueous solutions. Characterization of the membrane adsorber, analysis of the depyrogenation procedures and the evaluation of endotoxin removal efficiency in static mode are discussed. Ligand density of the membranes was around 7 mg/g dry membrane, allowing removal of up to 65% of the endotoxins. The performance of the membrane adsorber prepared using nylon coated with polyvinyl alcohol and containing histidine as the ligand proved superior to other membrane adsorbers reported in the literature. The lack of endotoxin adsorption on nylon membranes without histidine confirmed that endotoxin removal was due to the presence of the ligand at the membrane surface. Modified membranes were highly stable, exhibiting a lifespan of approximately thirty months

Membranas de transporte facilitado para separação de oxigênio utilizando biotransportadores

The aim of this work was to develop chemically stable carriers exhibiting high oxygen selectivity to be used in facilitated transport membranes for air fractioning. Strategies adopted in order to increase myoglobin stability were preparation of cobalt substituted proteins (CoMbs) and construction of recombinant proteins. Mutation designed by 29F68F resulted in a resistance to oxidation 3,5 times higher than that observed for a wild type myoglobin at 37 °C. To the 29F mutant, oxidation rate was 30% lower at these conditions. CoMbs exhibited a remarkable stability, at least ten times higher than the correspondent FeMb. Liquid membranes (LM) were obtained by impregnating a nylon microporous support with a myoglobin aqueous solution. Results were very promising. A LM containing a 60 g/L aqueous solution of native myoglobin showed an O2 permeability of 1600 Barrer and all O2/N2 selectivity of 21, at 25 °C and 3 cmHg. On the other hand, membranes made of Polyvinylalcohol (PVA) constituted a good altemative to the problem of lack of operational stability exhibited by LM. Besides, immobilization of myoglobin in a polymeric matrix promoted an extra stabilization against autoxidation, giving half-life times about 3 times higher than those for myoglobin in solution. Halflife time of a 29F CoMb immobilized in a PVA membrane at 7 °C was estimated as being as high as 3 years.Neste trabalho, foi investigado o uso de mioglobina em membranas de transporte facilitado para separação de oxigênio. As estratégias investigadas para estabilizar a mioglobina contra a autoxidação foram: produção de proteínas recombinantes e substituição do centro metálico de ferro para cobalto. Uma das mioglobinas mutantes produzidas (a mutante dupla 29F68F) apresentou uma redução de 3,5 vezes na taxa de autoxidação a 37 °C, comparativamente à mioglobina selvagem, enquanto para outra mutante simples (a mioglobina 29F), a taxa de oxidação foi 30% menor. Com a substituição por cobalto, o tempo de meia-vida passou de 13 h para mais de 96 h. Os resultados obtidos com as membranas líquidas foram bastante expressivos. Para a pressão de 3 cmHg, obteve-se uma permeabilidade ao O2 de 1600 Barrer e uma seletividade de 21 com uma membrana líquida contendo 60 g/L de mioglobina nativa de baleia. Membranas de poliálcoolvinílico (PVA) contendo mioglobina apresentaram desempenho semelhante às membranas líquidas. Além disto, a imobilização promoveu uma estabilização contra a autoxidação da mioglobina de até 3 vezes. O tempo de meia-vida para a cobalto-mioglobina mutante 29F imobilizada em uma membrana de PVA operada a 7 °C foi estimado com sendo superior a 3 anos. Este resultado, aliado ao bom desempenho das membranas em termos de permeabilidade e seletividade, constitui uma contribuição significativa no campo de separação de oxigênio utilizando membranas de transporte facilitado

Evaluation of the stability of concentrated emulsions for lemon beverages using sequential experimental designs.

The study of the stability of concentrated oil-in-water emulsions is imperative to provide a scientific approach for an important problem in the beverage industry, contributing to abolish the empiricism still present nowadays. The use of these emulsions would directly imply a reduction of transportation costs between production and the sales points, where dilution takes place. The goal of this research was to evaluate the influence of the main components of a lemon emulsion on its stability, aiming to maximize the concentration of oil in the beverage and to correlate its physicochemical characteristics to product stability, allowing an increase of shelf life of the final product. For this purpose, analyses of surface and interface tension, electrokinetic potential, particle size and rheological properties of the emulsions were conducted. A 2(4-1) fractional factorial design was performed with the following variables: lemon oil/water ratio (30% to 50%), starch and Arabic gum concentrations (0% to 30%) and dioctyl sodium sulfosuccinate (0 mg/L to 100 mg/L), including an evaluation of the responses at the central conditions of each variable. Sequentially, a full design was prepared to evaluate the two most influential variables obtained in the first plan, in which concentration of starch and gum ranged from 0% to 20%, while concentration of lemon oil/water ratio was fixed at 50%, without dioctyl sodium sulfosuccinate. Concentrated emulsions with stability superior to 15 days were obtained with either starch or Arabic gum and 50% lemon oil. The most stable formulations presented viscosity over 100 cP and ratio between the surface tension of the emulsion and the mucilage of over 1. These two answers were selected, since they better represent the behavior of emulsions in terms of stability and could be used as tools for an initial selection of the most promising formulations

Use of Hydrophilic Monomers to Avoid Secondary Particle Nucleation in Miniemulsion Polymerizations of Methyl Methacrylate

Miniemulsion polymerization is widely used to produce polymer nanoparticles. In many applications, it is important to ensure the narrow particle size distribution of the final product, which means that secondary micellar and homogeneous nucleation must be avoided during the reaction course. The present study proposes the use of hydrophilic comonomers to inhibit the occurrence of secondary particle nucleation in miniemulsion polymerizations of methyl methacrylate. Acrylic acid, metacrylic acid, 2-hydroxy ethyl methacrylate and methacrylamide were used as hydrophilic comonomers. It was observed that the use of small amounts of hydrophilic comonomers in miniemulsion polymerizations promoted by oil-soluble initiators could prevent secondary particle nucleation and lead to products with more homogeneous particle size distributions

Responses obtained in the 2^4-1 fractional factorial experimental design and triplicate at the central points to calculate the average, standard deviation and relative standard deviation.

<p>Responses obtained in the 2^4-1 fractional factorial experimental design and triplicate at the central points to calculate the average, standard deviation and relative standard deviation.</p

Membrane adsorber for endotoxin removal

ABSTRACT The surface of flat-sheet nylon membranes was modified using bisoxirane as the spacer and polyvinyl alcohol as the coating polymer. The amino acid histidine was explored as a ligand for endotoxins, aiming at its application for endotoxin removal from aqueous solutions. Characterization of the membrane adsorber, analysis of the depyrogenation procedures and the evaluation of endotoxin removal efficiency in static mode are discussed. Ligand density of the membranes was around 7 mg/g dry membrane, allowing removal of up to 65% of the endotoxins. The performance of the membrane adsorber prepared using nylon coated with polyvinyl alcohol and containing histidine as the ligand proved superior to other membrane adsorbers reported in the literature. The lack of endotoxin adsorption on nylon membranes without histidine confirmed that endotoxin removal was due to the presence of the ligand at the membrane surface. Modified membranes were highly stable, exhibiting a lifespan of approximately thirty months

Results for emulsion/mucilage surface tension ratio.

<p>(a) Response surface obtained from the model for γ emulsion/ γ mucilage (= <i>1</i>.<i>200</i> + <i>0</i>.<i>291</i> x₁ + <i>0</i>.<i>197</i> x₂, where x₁ and x₂ are the normalized values of starch and Arabic gum concentrations). (b) Curve of the emulsion/mucilage surface tension ratio versus stability after 15 days.</p

Responses obtained in the two-level full-factorial experimental design to evaluate the effects of starch and Arabic gum concentrations.

<p>Triplicate in the central points were used to calculate the average, standard deviation and relative standard deviation.</p><p>Responses obtained in the two-level full-factorial experimental design to evaluate the effects of starch and Arabic gum concentrations.</p