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.471102109CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQSem informaçã

Identification of pesticide-degrading Pseudomonas strains as poly-β-hydroxybutyrate producers

Polyhydroxybutyrate (PHB) is an ecological promising substitute for polypropylene because it is biocompatible, biodegradable and can be produced by renewable sources. This study investigated PHB accumulation on pesticide-degrading Pseudomonas. 14 strains of pesticide-degrading Pseudomonas isolated from subtropical lowland soil in southern Brazil were analyzed using optical microscopy. Lipid inclusions were identified in four strains, and three of them, which degraded the pesticide carbofuran, had extensive granules accumulation which was detected by transmission electron microscopy. These strains were cultivated in a shaker at 28°C and the polymer was characterized by Fourier transform infrared (FTIR) spectroscopy. Strain CMM43 had the best accumulation after 48 h. The biopolymer was identified as poly-β-hydroxybutyrate.Key words: Polyhydroxybutyrate (PHB), pesticide-degrading Pseudomonas sp., microscopy, subtropical lowland soil

Segmentation and Classification of Cine-MR Images Using Fully Convolutional Networks and Handcrafted Features

Three-dimensional cine-MRI is of crucial importance for assessing the cardiac function. Features that describe the anatomy and function of cardiac structures (e.g. Left Ventricle (LV), Right Ventricle (RV), and Myocardium(MC)) are known to have significant diagnostic value and can be computed from 3D cine-MR images. However, these features require precise segmentation of cardiac structures. Among the fully automated segmentation methods, Fully Convolutional Networks (FCN) with Skip Connections have shown robustness in medical segmentation problems. In this study, we develop a complete pipeline for classification of subjects with cardiac conditions based on 3D cine-MRI. For the segmentation task, we develop a 2D FCN and introduce Parallel Paths (PP) as a way to exploit the 3D information of the cine-MR image. For the classification task, 125 features were extracted from the segmented structures, describing their anatomy and function. Next, a two-stage pipeline for feature selection using the LASSO method is developed. A subset of 20 features is selected for classification. Each subject is classified using an ensemble of Logistic Regression, Multi-Layer Perceptron, and Support Vector Machine classifiers through majority voting. The Dice Coefficient for segmentation was 0.95+-0.03, 0.89+-0.13, and 0.90+-0.03 for LV, RV, and MC respectively. The 8-fold cross validation accuracy for the classification task was 95.05% and 92.77% based on ground truth and the proposed methods segmentations respectively. The results show that the PPs increase the segmentation accuracy, by exploiting the spatial relations. Moreover, the classification algorithm and the features showed discriminability while keeping the sensitivity to segmentation error as low as possible.Comment: 9 pages, 3 figures, 2 tables. Was accepted to the ACDC challenge, MICCAI 2017 (not attended

Reologia de Xantana: uma revisão sobre a influência de eletrólitos na viscosidade de soluções aquosas de gomas xantana

Diversas cepas de Xanthomonas campestris são capazes de produzir um biopolímero bacteriano denominado xantana, o qual é amplamente utilizado na indústria alimentícia. Para uma efetiva aplicação da xantana na indústria fazem-se necessários conhecimentos relacionados às propriedades químicas e à adição de eletrólitos, bem como seus efeitos nas características reológicas da solução de xantana. A cada novo biopolímero bacteriano sintetizado, surgem novos comportamentos reológicos, assim se faz necessário sua avaliação para posterior aplicação industrial. O presente trabalho tem como propósito revisar aspectos da estrutura química da xantana, efeitos da adição de eletrólitos e suas influências sobre a viscosidade apresentada por suas soluções

Evaluation of physical and chemical characteristics of xanthan gums

This work aimed at evaluating the physical and chemical characteristics of the xanthan produced by Xanthomonas arboricola pv pruni strain 115, and at comparing it with two xanthans obtained from commercial sources – Kelzan e Roeper. The analyzed xanthans showed specified patterns mentioned in the literature, except for low pyruvic acid content in the xanthan produced by strain 115, low monovalent salt content in the Roeper sample and high divalent salt content in both commercial samples. The low pyruvic acid content in the xanthan produced by X. arboricola pv pruni 115 did not affect the aqueous solution viscosity. Thus, the xanthan produced by strain 115 show physical and chemical characteristics that allow its use by the petroleum industry, as well as, in food, pharmaceutical and cosmetics products. Xanthomonas arboricola pv pruni. Xanthan. Physical and chemical characteristics

Avaliação das características físicas e químicas de gomas xantanas

O trabalho objetivou avaliar as características físicas e químicas da xantana produzida por Xanthomonas arboricola pv pruni cepa 115, comparando-a com duas xantanas obtidas de fontes comerciais – Kelzan e Roeper. As xantanas analisadas apresentaram-se dentro dos padrões especificados pela literatura, exceto pelo baixo conteúdo de ácido pirúvico da xantana produzida pela cepa 115, baixo conteúdo de sais monovalentes da amostra Roeper e alto conteúdo de sais divalentes das duas amostras comerciais. A baixa concentração de ácido pirúvico na xantana produzida por X. arboricola pv pruni 115 não influenciou na viscosidade da solução aquosa. Assim concluímos que a xantana produzida pela cepa 115 apresenta características físicas e químicas que permitem sua utilização na indústria de petróleo, como também para fins alimentícios, farmacêuticos e cosméticos

Seleção de linhagens de Xanthomonas campestris para a produção de goma xantana

Pesquisas para a descoberta de novas cepas produtoras do biopolímero vêm despertando o interesse de inúmeros pesquisadores, que procuram por microrganismos com capacidade de produção de goma e qualidade superiores às existentes. O estudo em questão selecionou os patovares X. campestris pv. manihotis 280-95, X. campestris pv. begoniae 1138-95 e X. campestris pv. dieffenbachiae 1429-00, como os de melhor desempenho, com uma produção de goma xantana de 10,8 g/L, 9,0 g/L e 8,5 g/L, respectivamente. Sendo a linhagem 280-95 a de melhor desempenho em produção e qualidade. O estresse alcalino aplicado no processo de produção da goma xantana da X. campestris pv. manihotis 280-95, aumentou em 40,76% a produção da goma, merecendo um estudo mais profundo, a fim de determinar as melhores condições para a aplicação desse processo