Claire Tondo Vendruscolo

Estudo da produção de biopolímeros via enzimática através de inativação e lise celular e com células viáveis de Beijerinckia sp. 7070

Microbial biopolymers are polysaccharides produced by microorganisms. Beijerinckia sp. 7070 produces the biopolymer denominated as clairana®. Microbial biopolymers can be produced using purified enzymes (by enzymatic pathway). The aim of this work was to evaluate the possibility to produce the clairana® biopolymer using purified enzymes, to verify if the synthesis and the enzymes involved in the synthesis are intra and/or extracellular, if the enzymes remain active in the medium and to study biopolymer production by enzymatic pathway, through cellular inactivation and lyse, and through conventional process with viable cells. The samples were cultivated with bacteria in liquid medium, and subjected to cellular death through cellular inactivation and lyse after 30h, by antibiotic and ultrasom, respectively. Samples were removed 32, 46 e 54h after incubation period, together with samples produced with viable cells. The same procedure was performed after 46h and samples collected after 48, 52 e 54h of incubation period. The polymers were recovered, dried, weighed and analyzed. The results suggest that it is possible to produce the clairana® biopolymer by enzymatic pathway and that, probably, intra and extracellular enzymes are involved, remaining active in the medium and beginning to act before 30h of fermentation. The enzymatic pathway process through cellular lyse is more effective, because it releases the polysaccharides intracellularly produced to medium.

Determinação das constantes cinéticas de degradação do ácido ascórbico em purê de pêssego: efeito da temperatura e concentração

Ascorbic acid (vitamin C) is extensively used in the food industry, not only for its nutritional value, but also for its many functional contributions to product quality. There have been many studies on the stability of ascorbic acid in different beverages, but no study was found on the reaction rate constants for ascorbic acid degradation in peach puree. In this work, the degradation of ascorbic acid in Jade peach puree was studied in anaerobic conditions and from 70-90 °C. The peach puree concentrations tested were 12, 22 and 32 °Brix. The kinetic analysis of the data suggests that the degradation was significantly represented by zero and first-order kinetic models. The rate of ascorbic acid degradation in peach puree was temperature dependent. The average activation energy was 45 kJ.mol-1 and independent of the concentration of soluble solids.

Structural studies of CV-70 polysaccharide

The goal of this paper is the characterization of the chemical structure of the water-soluble polysaccharide, CV-70, produced by bacteria Beijerinckia sp. Beijerinckia sp. is a genus of gram-negative, aerobic bacteria, usually found in sugar cane root. The CV-70 polysaccharide was produced in a fermentation medium containing 5% sucrose as the carbon source, tryptose and salts, at 25 degrees C [1]. The polysaccharide was hydrolyzed with 2 N trifluoroacetic acid at 100 degrees C for 16 h, purified, and analyzed by HPLC. Index of refraction was used for the detection of sugars. For GC-MS analysis, the CV-70 polysaccharide was derivatized through methylation and acetylation. Together with the GC-MS data, periodate oxidation studies were used to determine the possible glucosidic linkages. Carbon-13 NMR studies were carried out with hydrolyzed and silylated samples. Glucose, galactose and fucose were identified as the components in the CV-70 polysaccharide, in a 3:1:3 ratio.

Concentration Regimes of Biopolymers Xanthan, Tara, and Clairana, Comparing Dynamic Light Scattering and Distribution of Relaxation Time

The aim of this work was to evaluate the utilization of analysis of the distribution of relaxation time (DRT) using a dynamic light back-scattering technique as alternative method for the determination of the concentration regimes in aqueous solutions of biopolymers (xanthan, clairana and tara gums) by an analysis of the overlap (c*) and aggregation (c**) concentrations. The diffusion coefficients were obtained over a range of concentrations for each biopolymer using two methods. The first method analysed the behaviour of the diffusion coefficient as a function of the concentration of the gum solution. This method is based on the analysis of the diffusion coefficient versus the concentration curve. Using the slope of the curves, it was possible to determine the c* and c** for xanthan and tara gum. However, it was not possible to determine the concentration regimes for clairana using this method. The second method was based on an analysis of the DRTs, which showed different numbers of relaxation modes. It was observed that the concentrations at which the number of modes changed corresponded to the c* and c**. Thus, the DRT technique provided an alternative method for the determination of the critical concentrations of biopolymers.

Insights into the genome of the xanthan-producing phytopathogen Xanthomonas arboricola pv. pruni 109 by comparative genomic hybridization

The phytopathogenic bacterium Xanthomonas arboricola pv. pruni is the causal agent of Prunus Bacterial Spot disease that infects cultivated Prunus species and their hybrids. Furthermore, X. arboricola pv. pruni (Xap) plays a role in biotechnology since it produces xanthan gum, an important biopolymer used mainly in the food, oil, and cosmetics industry. To gain first insights into the genome composition of this pathovar, genomic DNA of X. arboricola pv. pruni strains was compared to the genomes of reference strains X. campestris pv. campestris B100 (Xcc B100) and X. campestris pv. vesicatoria 85-10 (Xcv 85-10) applying microarray-based comparative genomic hybridizations (CGH). The results implied that X. arboricola pv. pruni 109 lacks 6.67% and 5.21% of the genes present in the reference strains Xcc B100 and Xcv 85-10, respectively. Most of the missing genes were found to be organized in clusters and do not belong to the core genome of the two reference strains. Often they encode mobile genetic elements. Furthermore, the absence of gene clusters coding for the lipopolysaccharide (LPS) O-antigens of Xcc B100 and Xcv 85-10 indicates that the structure of the O-antigen of X. arboricola pv. pruni 109 differs from that of Xcc B100 and Xcv 85-10.

Comportamento reológico de xantana produzida por Xanthomonas arboricola pv pruni para aplicação em fluido de perfuração de poços de petróleo

The aim of this work was to evaluate xanthans produced by Xanthomonas arboricola pv pruni to be used for increasing the viscosity of fluids applied in the perforation of oil wells, which were compared with three commercial samples. In order to do that, the viscosity of aqueous and saline solutions (NaCl, KCl and CaCl2) from different xanthans, at different temperatures (25, 45, 65 and 80 oC), was determined in a rheometer. The rheological parameters consistency index (K) and flow behaviour index (n) were obtained by adjusting the data with the Ostwald-de-Waelle model. Gel strength (G0, G10 e G30) was determined in a viscometer, and the concentration of monovalent (sodium and potassium) and divalent salts (calcium and magnesium) was determined in flame photometer and in atomic absorption spectrometer, respectively. Taken together, the results obtained in this study showed that xanthans produced by patovar pruni, Xp 106-600 and Xp 115-600, are promising for fluids used in oil well perforation with saline solutions, because they have low concentration of salts. As for the commercial polymers, they presented the best results when used in aqueous solution, because they had high salt concentrations.

Structure of xanthan gum and cell ultrastructure at different times of alkali stress

The effect of alkali stress on the yield, viscosity, gum structure, and cell ultrastructure of xanthan gum was evaluated at the end of fermentation process of xanthan production by Xanthomonas campestris pv. manihotis 280-95. Although greater xanthan production was observed after a 24 h-alkali stress process, a lower viscosity was observed when compared to the alkali stress-free gum, regardless of the alkali stress time. However, this outcome is not conclusive as further studies on gum purification are required to remove excess sodium, verify the efficiency loss and the consequent increase in the polymer viscosity. Alkali stress altered the structure of xanthan gum from a polygon-like shape to a star-like form. At the end of the fermentation, early structural changes in the bacterium were observed. After alkali stress, marked structural differences were observed in the cells. A more vacuolated cytoplasm and discontinuities in the membrane cells evidenced the cell lysis. Xanthan was observed in the form of concentric circles instead of agglomerates as observed prior to the alkali stress.

INFLUÊNCIA DA CULTIVAR NAS CARACTERÍSTICA FÍSICAS, QUÍMICAS E SENSORIAIS DE TOPPING DE MIRTILO

O objetivo deste trabalho foi avaliar a influencia da cultivar de mirtilo nas caracteristicas fisicas, quimicas e sensoriais de topping de mirtilo. Seis cultivares foram testadas: Woodard, Powderblue, Briteblue, Bluegem, Bluebelle e Delite. As frutas e toppings foram submetidos a analises quimicas, fisicas e sensoriais. O teor de antocianinas totais foi determinado por espectrofotometria. O maior teor de antocianinas foi encontrado nas frutas e no topping da cultivar Powderblue. Nao houve correlacao entre o teor de antocianinas das frutas e dos toppings de cada cultivar. Todas as cultivares utilizadas neste estudo podem ser empregadas na elaboracao de topping, com boa aceitabilidade sensorial.

Chemical deacetylation natural xanthan (Jungbunzlauer

With the aim of adapting a method for removal of acetyl groups from xanthan, reactions of chemical deacetylation were carried out with natural xanthan (Jungbunzlauer®) with variations on the following parameters: biopolymer and alkali concentration (sodium and potassium hydroxide). The deacetylation reaction was performed at 25 oC for three hours. The proposed methodology was efficient to promote the deacetylation reaction. The viscosity of xanthan increased when the alkali concentration was higher in the deacetylation reaction. Xanthan concentration in the solution used in the deacetylation reaction did not influence the solutions viscosity, as similar results in both tested biopolymer concentrations (0.5 and 1%) were obtained for all experiments in different shear rates. Deacetylation reactions at 25 oC for three hours with sodium and potassium hydroxide in 0.01 mol.L-1 showed a viscosity of 410 and 420 mPa.s at 10 s-1 and acetylation degree 1.3 e 1.4%, respectively.

EFEITO DA GOMA XANTANA NAS CARACTERÍSTICAS SENSORIAIS DE BOLOS SEM GLÚTEN

O objetivo deste trabalho foi avaliar o efeito da goma xantana nas caracteristicas sensoriais de bolos sem gluten feitos com farinhas de arroz e milho. Quatro formulacoes foram testadas: (F1) controle - sem xantana, (F2) com 0,2% de xantana, (F3) com 0,3% de xantana e (F4) com 0,4% de xantana. As formulacoes foram elaboradas com farinha de arroz, de milho, acucar, leite, ovos, oleo de soja, xantana e fermento quimico. A massa foi preparada, colocada em formas e assada a 200oC por 35 minutos. A caracterizacao sensorial foi realizada com 13 julgadores treinados que avaliaram nove atributos do bolo: cor do miolo, formacao de migalhas, elasticidade, firmeza, porosidade, sabor de arroz, sabor de milho, sensacao de umidade na boca e envelhecimento; esta caracterizacao foi realizada com bolos frescos e armazenados durante 3, 6 e 9 dias. Para a realizacao desta etapa foi utilizada uma escala nao estruturada de 9cm. A adicao de xantana melhorou as caracteristicas sensoriais dos bolos, marcadamente retardando o envelhecimento, reduzindo a formacao de migalhas e aumentando a sensacao de umidade na boca, sendo que as amostras com 0,3% e 0,4% de xantana tiveram as melhores caracteristicas. Portanto, a goma xantana pode ser utilizada de maneira satisfatoria na producao de bolos isentos de gluten, melhorando expressivamente as caracteristicas e, assim, sua qualidade sensorial.