147 research outputs found
Continuous production of isovaleraldehyde through extractive bioconversion in a hollow-fiber membrane bioreactor
No full textA membrane bioreactor was developed to perform an extractive bioconversion aimed at the production of isovaleraldehyde by isoamyl alcohol oxidation with whole cells of Gluconobacter oxydans. A liquid/liquid extractive system using isooctane as extractant and assisted by a hollow-fiber hydrophobic membrane was chosen to recover the product. The aqueous bioconversion phase and the organic phase were maintained apart with the aid of the membrane. The extraction of alcohol and aldehyde was evaluated by performing equilibrium and mass transfer kinetic studies. The bioprocess was then performed in a continuous mode with addition of the substrate to the aqueous phase. Fresh solvent was added to the organic phase and exhausted solvent was removed at the same flow rate. The extractive system enabled a fast and selective in situ removal of the aldehyde from the water to the organic phase. High conversions (72–90%) and overall productivity (2.0–3.0 g l−1 h−1) were obtained in continuous experiments performed with different rates of alcohol addition (1.5–3.5 g l−1 h−1). Cell deactivation was observed after 10–12 h of operation
Continuous production and in situ extraction of isovaleraldehyde in a membrane bioreactor
No full textBioconversions are generally low productivity processes when compared to chemical synthetic reactions. The productivity of a bioconversion can be maximized if it is carried out in the presence of substrate/product concentrations at which the biocatalyst shows optimal activity and stability. One way to achieve this is to develop a process with continuous addition of the substrate and selective removal of the product. The microbial oxidation of isoamyl alcohol to isovaleraldehyde by a newly isolated Gluconobacter oxydans strain has been reported recently. High conversion yields (>90%) and good rates (maximum yield after 90 min) were obtained in a batch mode. With this strain, although aldehyde dehydrogenase(s) leading to acid formation are present, further oxidation of the aldehyde to acid is significantly slower so that transient accumulation of the aldehyde is possible. The productivity of this bioconversion can be improved by setting up a continuous process with addition of substrate at an adequate flow rate. In situ removal of the aldehyde is imperative to avoid acid production and to reduce evaporation of the product. This chapter describes a membrane-based extractive procedure to achieve an in situ, nondispersive recovery of the aldehyde
Biotransformations in two-liquid phase systems: production of phenylacetaldehyde by oxidation of 2-phenylethanol with acetic acid bacteria
No full textPhenylacetaldehyde can be obtained by oxidation of 2-phenylethanol with acetic acid bacteria in two-liquid-phase systems where the aldehyde is removed into the organic phase before its further conversion to acid. Two Acetobacter strains (ALEF and ALEG) were able to accumulate aldehyde when aliphatic hydrocarbons were used. A two-liquid-phase system, composed of water and isooctane (v/v, 1/1), was particularly suited for a significant accumulation of the aldehyde: Acetobacter sp. ALEG furnished 9 g/l of phenylacetaldehyde within 4 h starting from 10 g/l of alcohol and still 8 g/l were recovered after 24 h in the organic phase, whereas strain ALEF gave 3.5 g/l of aldehyde from 5.0 g/l of substrate. Acetobacter sp. ALEG also showed satisfactory long-term stability, being able to perform the transformation with 80% of the original activity after 3 days of contact with the solvent
Enantioselective oxidation of (RS)-2-phenyl-1-propanol to (S)-2-phenylpropanoic acid with Gluconobacter oxydans: Simplex optimization of the biotransformation
No full textThe microbial oxidation of racemic 2-phenyl-1-propanol by Gluconobacter oxydans DSM 50049 was investigated. Whole bacterial cells were used to produce (S)-(+)-2-phenylpropanoic acid with high enantiomeric excess (E>200). A simplex sequential method was employed as an experimental design to guide the optimization process. Temperature of 26-28°C, pH 6.0-6.2, substrate concentration of 20-25 mM and agitation of 150 rpm have been found the best conditions to achieve the highest reaction rates and enantioselectivities
Bioluminescence in G protein-coupled receptors drug screening using nanoluciferase and halo-tag technology
No full textHere we describe the stepwise application of bioluminescence resonance energy transfer (BRET)-based conformational receptor biosensors to study GPCR activation in intact cells. This technology can be easily adopted to various plate reader devices and microtiter plate formats. Due to the high sensitivity of these BRET-based receptor biosensors and their ability to quantify simultaneously receptor activation/de-activation kinetics as well as compound efficacy and potency, these optical tools provide the most direct and unbiased approach to monitor GPCR activity in a high-throughput-compatible assay format, representing a novel promising tool for the discovery of potential GPCR therapeutics
Imaging of Genetically Encoded FRET-Based Biosensors to Detect GPCR Activity
No full textA wealth of assays for screening GPCR activity have been developed. Biosensors that employ Förster Resonance Energy transfer (FRET) are specific and enable dynamic measurements. Moreover, FRET biosensors are ideally suited for the analysis of single living cells. The FRET biosensors described in this manuscript are entirely genetically encoded by plasmids. Here, protocols for employing FRET-based biosensors to detect G protein activity upon GPCR activation are reported. The protocols include details on the isolation of plasmids, transfection, generation of stable cell lines with the FRET biosensors, FRET ratio imaging, and data analysis.</p
The Deconstruction of the Feminine in Uma aprendizagem ou O livro dos prazeres
No full textO presente artigo visa à análise do processo de ressignificação do conceito de feminino e da constituição da protagonista como sujeito do livro Uma aprendizagem ou O livro dos prazeres, de Clarice Lispector.
Para esse fim, far-se-á um breve estudo da linguagem usada pela autora à luz da hermenêutica, da psicanálise lacaniana e de teorias feministas de autoras como Simone de Beauvoir e Virginia Woolf. Assim, expõem-se os questionamentos dos padrões históricos, sociais e culturais de gênero e as quebras de paradigmas, tanto conceituais como estilísticos de que lançam mão a autora.
Será analisada uma passagem do romance para exemplificar a complexidade da obra em relação ao tema em questão e mostrar como ocorre uma desmontagem de estereótipos e o valor estético do livro.This article aims at analyzing the resignification process of the concept of feminine and the constitution of the protagonist as the subject of the novel Uma aprendizagem ou O livro dos prazeres, by Clarice Lispector.
To this end, we will make a brief study of the language used by the author through a close reading of the text, making use of some analogical affinities with Lacanian psychoanalysis. Thus, we will expose the questioning of historical, social and cultural gender patterns and the paradigm breaks, both conceptual and stylistic, used by the author.
By analyzing an excerpt from the novel, we hope to showcase the novel\u27s complexity regarding the theme and demonstrate how stereotypes are taken down and show the work\u27s aesthetic value
Hydrophobic interaction chromatography
No full textMost proteins and large polypeptides have hydrophobic regions at their surface. These hydrophobic ‘patches’ are due to the presence of the side chains of hydrophobic or non-polar amino acids such as phenylalanine, tryptophan, alanine and methionine. These surface hydrophobic regions are interspersed between more hydrophilic or polar regions and the number, size and distribution of them is a specific characteristic of each protein. Hydrophobic Interaction Chromatography (HIC) is a commonly used technique that exploits these hydrophobic features of proteins as a basis for their separation even in complex biological mixtures (1) (2). In general the conditions under which hydrophobic interaction chromatography is used are relatively mild and ‘protein friendly’ resulting in good biological recoveries. Hydrophobic binding is relatively strong and is maintained even in the presence of chaotrophic agents, organic solvents and detergents. For these reasons this technique has a widespread use for the purification of proteins and large polypeptides
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