Efficient biotechnological synthesis of flavor esters using a low-cost biocatalyst with immobilized Rhizomucor miehei lipase.

In this work, the synthesis of two fruit flavor esters, namely methyl and ethyl butyrate, by lipase from Rhizomucor miehei immobilized onto chitosan in the presence of the surfactant sodium dodecyl sulfate SDS was investigated. In the optimized conditions, maximum esterification yield for ethyl butyrate and methyl butyrate was (92 ± 1%) and (89 ± 1%), respectively. Esterification yields for both reactions were comparable or even superior to the ones achieved when the synthesis was catalyzed by a commercial enzyme, Lipozyme®, at the same reaction conditions. For ethyl butyrate, the developed biocatalyst was used for seven consecutive cycles of reaction with retention of its catalytic activity. For methyl butyrate synthesis the biocatalyst was used for four consecutive cycles without loss of its catalytic activity. The results show that chitosan may be employed in obtaining biocatalysts with high catalytic efficiency and can successfully replace the currently commercial available biocatalysts.

Effect of the Presence of Surfactants and Immobilization Conditions on Catalysts' Properties of Rhizomucor miehei Lipase onto Chitosan.

Lipase from Rhizomucor miehei (RML) was immobilized onto chitosan support in the presence of some surfactants added at low levels using two different strategies. In the first approach, the enzyme was immobilized in the presence of surfactants on chitosan supports previously functionalized with glutaraldehyde. In the second one, after prior enzyme adsorption on chitosan beads in the presence of surfactants, the complex chitosan beads-enzyme was then cross-linked with glutaraldehyde. The effects of surfactant concentrations on the activities of free and immobilized RML were evaluated. Hexadecyltrimethylammonium bromide (CTAB) promoted an inhibition of enzyme activity while the nonionic surfactant Triton X-100 caused a slight increase in the catalytic activity of the free enzyme and the derivatives produced in both methods of immobilization. The best derivatives were achieved when the lipase was firstly adsorbed on chitosan beads at 4 °C for 1 h, 220 rpm followed by cross-link the complex chitosan beads-enzyme with glutaraldehyde 0.6% v.v-1 at pH 7. The derivatives obtained under these conditions showed high catalytic activity and excellent thermal stability at 60° and 37 °C. The best derivative was also evaluated in the synthesis of two flavor esters namely methyl and ethyl butyrate. At non-optimized conditions, the maximum conversion yield for methyl butyrate was 89%, and for ethyl butyrate, the esterification yield was 92%. The results for both esterifications were similar to those obtained when the commercial enzyme Lipozyme® and free enzyme were used in the same reaction conditions and higher than the one achieved in the absence of the selected surfactant.

Immobilization of CALB on activated chitosan: Application to enzymatic synthesis in supercritical and near-critical carbon dioxide.

The objective of this new paper was to evaluate the enzymatic esterification reaction conducted in supercritical or near-critical CO2, catalyzed by immobilized lipase B from Candida antarctica (CALB). The biocatalyst was prepared through the immobilization of CALB by covalent attachment using chitosan sequentially activated with Glycidol, ethylenediamine (EDA) and glutaraldehyde as support. In order to determine the best operational conditions of the esterification reaction (1: 1 (alcohol-acid); biocatalyst content, 10% (by substrate mass); 45 °C), an experimental design (23) was conducted to evaluate the effects of the following parameters: alcohol to oil molar ratios, reaction time and temperature. The maximum loading of chitosan was 20 mg protein/g support, and the thermal and solvent stability of the new biocatalyst was higher than that of the CALB-GX (by a 26-fold factor), CALB-OC (by a 53-fold factor) and Novozym 435 (by a 3-fold factor). The maximum conversion was 46.9% at a temperature of 29.9 °C, ethanol to oleic acid molar ratio equal to 4.50:1, and a reaction time of 6.5 h. Additionally, the removal of water from the medium, by using molecular sieves, promoted a 16.0% increase in the conversion of oleic acid into ethyl esters.

Extraction of lipids from microalgae by ultrasound application: prospection of the optimal extraction method.

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20-50% of dry weight) of lipids. A successful and economically viable algae based oil industry will depend on the selection of appropriate microalgal strains and the selection of the most suitable lipid extraction method. In this paper, five extraction methods were evaluated regarding the extraction of lipids from Chlorella vulgaris: Bligh and Dyer, Chen, Folch, Hara and Radin, and Soxhlet. Furthermore, the addition of silica powder was studied to evaluate the introduction of more shear stress to the system as to increase the disruption of cell walls. Among the studied methods, the Bligh and Dyer method assisted by ultrasound resulted in the highest extraction of oil from C. vulgaris (52.5% w/w). Addition of powder silica did not improve the extraction of oil.

O saber e a verdade na Psicanálise e na Universidade / Knowledge and truth in Psychoanalysis and in the University / El saber y la verdad en el Psicoanálisis y en la Universidad

O autor realiza uma discussão acerca da posição da psicanálise no âmbito da Universidade e em sua relação com a ciência. Para tanto, promove uma problematização sobre as relações históricas entre o saber e a verdade na estrutura desses discursos, apresentando uma argumentação que considera a função política do saber e da verdade na constituição do sujeito na modernidade. Para demonstrar a relação política e econômica entre ciência e capitalismo, de forma a fundamentar suas análises das apropriações que essas práticas e discursos realizam dessas categorias, articula proposições das obras de Lacan e Foucault, entendendo que essas análises históricas e genealógicas são necessárias para aprofundar o debate sobre as relações entre psicanálise, ciência e Universidade.(AU)

The author presents a discussion about the position of psychoanalysis within the university and its relationship to science. For that he promotes a questioning about the historical links between knowledge and truth in the structure of these speeches, presenting an argument that considers the political role of knowledge and truth in the constitution of the subject in modernity. To demonstrate the economic and political relationship between science and capitalism, in order to substantiate his analysis of the appropriations that these practices and discourses carry on these categories, he articulates propositions from the works of Lacan and Foucault, considering that these historical and genealogical analysis are necessary to deepen the debate on the relationship between psychoanalysis, science and academia.(AU)

El autor realiza una discusión acerca de la posición del psicoanálisis en el ámbito de la Universidad y en su relación con la ciencia. Para eso, promueve una problematización sobre las relaciones históricas entre el saber y la verdad en la estructura de esos discursos, presentando una argumentación que considera la función política del saber y de la verdad en la constitución del sujeto en la modernidad. Para demostrar la relación política y económica entre ciencia y capitalismo, de forma de fundamentar sus análisis de las apropiaciones que esas prácticas y discursos realizan de esas categorías, articula proposiciones de las obras de Lacan y Foucault, entendiendo que esos análisis históricos y genealógicos son necesarios para profundizar el debate sobre las relaciones entre psicoanálisis, ciencia y Universidad.(AU)

O saber e a verdade na Psicanálise e na Universidade / Knowledge and truth in Psychoanalysis and in the University / El saber y la verdad en el Psicoanálisis y en la Universidad

O autor realiza uma discussão acerca da posição da psicanálise no âmbito da Universidade e em sua relação com a ciência. Para tanto, promove uma problematização sobre as relações históricas entre o saber e a verdade na estrutura desses discursos, apresentando uma argumentação que considera a função política do saber e da verdade na constituição do sujeito na modernidade. Para demonstrar a relação política e econômica entre ciência e capitalismo, de forma a fundamentar suas análises das apropriações que essas práticas e discursos realizam dessas categorias, articula proposições das obras de Lacan e Foucault, entendendo que essas análises históricas e genealógicas são necessárias para aprofundar o debate sobre as relações entre psicanálise, ciência e Universidade...

The author presents a discussion about the position of psychoanalysis within the university and its relationship to science. For that he promotes a questioning about the historical links between knowledge and truth in the structure of these speeches, presenting an argument that considers the political role of knowledge and truth in the constitution of the subject in modernity. To demonstrate the economic and political relationship between science and capitalism, in order to substantiate his analysis of the appropriations that these practices and discourses carry on these categories, he articulates propositions from the works of Lacan and Foucault, considering that these historical and genealogical analysis are necessary to deepen the debate on the relationship between psychoanalysis, science and academia...

El autor realiza una discusión acerca de la posición del psicoanálisis en el ámbito de la Universidad y en su relación con la ciencia. Para eso, promueve una problematización sobre las relaciones históricas entre el saber y la verdad en la estructura de esos discursos, presentando una argumentación que considera la función política del saber y de la verdad en la constitución del sujeto en la modernidad. Para demostrar la relación política y económica entre ciencia y capitalismo, de forma de fundamentar sus análisis de las apropiaciones que esas prácticas y discursos realizan de esas categorías, articula proposiciones de las obras de Lacan y Foucault, entendiendo que esos análisis históricos y genealógicos son necesarios para profundizar el debate sobre las relaciones entre psicoanálisis, ciencia y Universidad...

Bioprospecting for oil producing microalgal strains: evaluation of oil and biomass production for ten microalgal strains.

Microalgae have the ability to grow rapidly, synthesize and accumulate large amounts (approximately 20-50% of dry weight) of lipids. A successful and economically viable algae based oil industry depends on the selection of appropriate algal strains. In this study ten species of microalgae were prospected to determine their suitability for oil production: Chaetoceros gracilis, Chaetoceros mulleri, Chlorella vulgaris, Dunaliella sp., Isochrysis sp., Nannochloropsis oculata, Tetraselmis sp., Tetraselmis chui, Tetraselmis tetrathele and Thalassiosira weissflogii. The study was carried out in 3 L glass flasks subjected to constant aeration and controlled artificial illumination and temperature at two different salinities. After harvesting, the extraction of oil was carried out using the Bligh and Dyer method assisted by ultrasound. Results showed that C. gracilis presented the highest oil content and that C. vulgaris presented the highest oil production.

A non-invasive assessment of hepatitis B virus carrier status using saliva samples.

A non-invasive testing method to determine hepatitis B virus (HBV) carrier status in pregnant women was evaluated. Paired serum and saliva samples were collected and assessment of hepatitis B markers were performed. Of the 502 women enrolled, 5.6% (28/502) of their sera were found to be positive for HBV surface antigen (HBsAg). Assessment of 28 HBsAg seroreactive and 200 HBsAg sero-non-reactive paired saliva samples showed that 17 saliva contained HBsAg. Fourteen of the saliva reactive samples were matched to the serum reactive samples (50% sensitivity); and 3 saliva samples were positive for HBsAg among 200 subjects seronegative for HBsAg (98.5% specificity). Seven of the 28 HBsAg positive sera were found to be reactive for HBV envelope antigen (HBeAg) (25%). One of seven HBeAg seroreactive and 16 HBeAg seronegative paired saliva samples tested were non-reactive for HBeAg. This report found a non-invasive saliva testing method to be a possible alternative approach for determining chronic HBV carrier status if the sensitivity of the test can be improved.