39,864 research outputs found

    Desarrollo de papeles biocativos por injerto de mol茅culas espec铆ficas en celulosa

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    Tesis (DCI)--FCEFN-UNC, 2019En la presente tesis se presenta el desarrollo de papeles bioactivos con potencial aplicaci贸n en el envasado activo de alimentos. Para tal fin, se propuso el injerto de eugenol, un compuesto de origen natural con propiedades antimicrobiana, antioxidante y repelente de insectos, en celulosa, utilizando 谩cido policarbox铆lico como agente ligante. Con el objetivo de evaluar la escalabilidad del proceso propuesto, se estudiaron distintas tecnolog铆as de curado, tales como calentamiento por convecci贸n, infrarrojo, microondas y conducci贸n. En todos los casos, se analizaron la influencia de las variables operativas sobre el avance de la reacci贸n y propiedades finales del papel preparado, utilizando un dise帽o de experimentos Doehlert para elegir las experiencias a realizar, y analizando los resultados mediante metodolog铆a de superficie de respuesta y an谩lisis estad铆stico ANOVA. Se pudo comprobar que la reacci贸n de injerto de eugenol en papel comercial se produjo con 茅xito en todas las tecnolog铆as estudiadas. Asimismo, se encontraron las condiciones 贸ptimas de reacci贸n para cada una de las tecnolog铆as, para lo cual se busc贸 un compromiso entre el avance de la reacci贸n y las propiedades finales del material (mec谩nicas y color). A partir de estas condiciones, se prepararon papeles y se realiz贸 una caracterizaci贸n m谩s espec铆fica para su aplicaci贸n como envase de alimentos comparando los papeles modificados con el papel virgen. Se analizaron las propiedades mec谩nicas por ensayo de tracci贸n, rasgado y punzonado y se midi贸 la absorci贸n de agua y la capacidad de degradaci贸n. Por otro lado, las propiedades bioactivas analizadas fueron la actividad antioxidante, antimicrobiana, repelente e insecticida de gorgojos (T. castaneum y R. dominica). Una vez probado que el papel modificado presenta buenas caracter铆sticas f铆sicas y bioactivas para su posible aplicaci贸n en el envasado de alimentos, se realizaron prototipos de envasado para harina, como alimento representativo de alimentos derivados de cereales, susceptibles al ataque de plagas. En este estudio se analiz贸 la migraci贸n de reactivos, propiedades organol茅pticas y conservaci贸n del alimento, arrojando resultados promisorios para la industria de envases de alimentos. Finalmente, se realiz贸 una comparaci贸n de las tecnolog铆as de curado ensayadas, analizando diferentes aspectos como avance de reacci贸n, propiedades finales, apariencia, tiempo de reacci贸n, consumo de energ铆a, entre otros, como as铆 tambi茅n disponibilidad y uso de estas tecnolog铆as a escala industrial, seleccionando la tecnolog铆a de conducci贸n como la m谩s adecuada para una propuesta de escalado industrial.Fil: Muratore, Florencia. Universidad Nacional de C贸rdoba. Facultad de Ciencias Exactas, F铆sicas y Naturales; Argentina.Fil: Muratore, Florencia. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas. Instituto de Investigaci贸n y Desarrollo en Ingenier铆a de Procesos y Qu铆mica Aplicada; Argentina

    Application of lactic acid bacteria for the biopreservation of meat products: A systematic review

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    .The increasing concern of consumers about food quality and safety and their rejection of chemical additives has promoted the breakthrough of the biopreservation field and the development of studies on the use of beneficial bacteria and their metabolites as potential natural antimicrobials for shelf life extension and enhanced food safety. Control of foodborne pathogens in meat and meat products represents a serious challenge for the food industry which can be addressed through the intelligent use of bio-compounds or biopreservatives. This article aims to systematically review the available knowledge about biological strategies based on the use of lactic acid bacteria to control the proliferation of undesirable microorganisms in different meat products. The outcome of the literature search evidenced the potential of several strains of lactic acid bacteria and their purified or semi-purified antimicrobial metabolites as biopreservatives in meat products for achieving longer shelf life or inhibiting spoilage and pathogenic bacteria, especially when combined with other technologies to achieve a synergistic effect.S

    Energia odnawialna w wojew贸dztwie pomorskim, 177 s.

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    Stan aktualny, perspektywy rozwoju i potencja艂 energii odnawialnej w wojew贸dztwie pomorskim. Analiza PEST energii odnawialnej

    Patterns and driving factors of leaf C, N, and P stoichiometry in two forest types with different stand ages in a mid-subtropical zone

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    Background: Carbon (C), nitrogen (N), and phosphorus (P) stoichiometry is a key indicator of nutrient utilization in plants, and C/N/P ratios are related to the life histories and adaptation strategies of tree species. However, no consensus has been reached on how leaf stoichiometric characteristics are affected by forest type and stand ages. The relationships between leaf stoichiometry and geographical, meteorological, and soil factors also remain poorly understood. Methods: Leaf and soil were sampled from forest stands of different age groups (young, middle-aged, near-mature, and mature) in two forest types (Chinese fir (Cunninghamia lanceolata) forests and evergreen broadleaved forests). The relationships between leaf C, N, and P stoichiometric parameters and geographical, meteorological, and soil factors were analysed by using redundancy analysis (RDA) and stepwise linear regression analysis. Results: Leaf C concentrations peaked in the near-mature stands with increasing age irrespective of forest type. Leaf N and P concentrations fluctuated with a rising trend in Chinese fir forests, while decreased first and increased later from young to mature phases in natural evergreen broadleaved forests. Chinese fir forests were primarily limited by N and P, while natural evergreen broadleaved forests were more susceptible to P limitation. Leaf C, N, and P stoichiometric characteristics in Chinese fir forests were mainly affected by the soil total P concentration (SP), longitude (LNG), growing season precipitation (GSP) and mean temperature in July (JUT). The leaf C concentration was mainly affected by GSP and JUT; leaf N and P concentrations were both positively correlated with LNG; and leaf P was positively correlated with SP. In evergreen broadleaved forests, however, leaf stoichiometric parameters displayed significant correlations with latitude (LAT) and mean annual precipitation (MAP). Conclusions: Leaf stoichiometry differed among forest stands of different age groups and forest types. Leaf C, N, and P stoichiometry was primarily explained by the combinations of SP, LNG, GSP and JUT in Chinese fir forests. LAT and MAP were the main controlling factors affecting the variations in the leaf C, N, and P status in natural evergreen broadleaved forests, which supports the temperature-plant physiological hypothesis. These findings improve the understanding of the distribution patterns and driving mechanisms of leaf stoichiometry linked with stand age and forest type

    Globalisation and pollinators: pollinator declines are an economic threat to global food systems

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    1. Trade in animal-pollinated crops plays an important role in global food systems: in many low-income countries, export of pollinated crops such as coffee and cocoa plays a significant role in livelihoods, while food systems in many higher income nations depend on international trade in these crops to satisfy their local demands. Losses of pollination services therefore pose a significant risk to economies beyond the area directly affected. 2. Using a simple extension of a common economic model, we explore which countries are most affected by a loss of pollination services in three case study groups of 25 countries that are vulnerable to different risks: pesticide use, natural disasters and economic debts. 3. In all three cases, large, developed economies such as the United Kingdom, Germany and Japan, are estimated to suffer the greatest economic losses, even if pollinator losses only affect smaller, less-developed economies. 4. In cases where higher income countries are affected by pollinator losses, there is a significant shift in the value of global pollinated crop production towards other large, unaffected countries. 5. Our findings highlight the need for richer countries to invest in pollinator conservation beyond their own borders to maintain resilient food systems. We provide suggestions for further economic research to better understand and identify system vulnerabilities to pollinator losses

    Efecto a medio plazo de la recurrencia de los incendios forestales en la regeneraci贸n post-fuego del pinar de Tabuyo del Monte

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    En el presente trabajo se pretende comparar la regeneraci贸n de la comunidad vegetal dominada por P. pinaster en Tabuyo del Monte (sierra delTeleno) en dos escenarios de recurrencia de incendios diferentes:una zona afectada por un solo incendio en los 煤ltimos cuarenta a帽os (recurrencia 1, incendio de 2012) y una zona afectada por dos incendios en los 煤ltimos cuarenta a帽os (recurrencia 2, incendio de 1998 y posteriormente incendio de 2012). Para ello se tomaron datos de porcentaje de suelo descubierto, cobertura vegetal por especies, por biotipos y por estrategia de regeneraci贸n (rebrotadoras y germinadoras), as铆 como distintas variables poblacionales de Pinus pinaster

    Identification of Hindbrain Neural Substrates for Motor Initiation in the hatchling Xenopus laevis Tadpole

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    Animal survival profoundly depends on the ability to detect stimuli in the environment, process them and respond accordingly. In this respect, motor responses to a sensory stimulation evolved into a variety of coordinated movements, which involve the control of brain centres over spinal locomotor circuits. The hatchling Xenopus tadpole, even in its embryonic stage, is able to detect external sensory information and to swim away if the stimulus is considered noxious. To do so, the tadpole relies on well-known ascending sensory pathway, which carries the sensory information to the brain. When the stimulus is strong enough, descending interneurons are activated, leading to the excitation of spinal CPG neurons, which causes the undulatory movement of swimming. However, the activation of descending interneurons that marks the initiation of motor response appears after a long delay from the sensory stimulation. Furthermore, the long-latency response is variable in time, as observed in the slow-summating excitation measured in descending interneurons. These two features, i.e. long-latency and variability, cannot be explained by the firing time and pattern of the ascending sensory pathway of the Xenopus tadpole. Therefore, a novel neuronal population has been proposed to lie in the hindbrain of the tadpole, and being able to 'hold' the sensory information, thus accounting for the long and variable delay of swim initiation. In this work, the role of the hindbrain in the maintenance of the long and variable response to trunk skin stimulation is investigated in the Xenopustadpole at developmental stage 37/38. A multifaceted approach has been used to unravel the neuronal mechanisms underlying the delayed motor response, including behavioural experiments, electrophysiology analysis of fictive swimming, hindbrain extracellular recordings and imaging experiments. Two novel neuronal populations have been identified in the tadpole's hindbrain, which exhibit activation patterns compatible with the role of delaying the excitation of the spinal locomotor circuit. Future work on cellular properties and synaptic connections of these newly discovered populations might shed light on the mechanism of descending control active at embryonic stage. Identifying supraspinal neuronal populations in an embryonic organism could aid in understanding mechanisms of descending motor control in more complex vertebrates

    Bioinformatic characterization of a triacylglycerol lipase produced by Aspergillus flavus isolated from the decaying seed of Cucumeropsis mannii

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    Lipases are enzymes of industrial importance responsible for the hydrolysis of ester bonds of triglycerides. A lipolytic fungus was isolated and subsequently identified based on the ITS sequence analysis as putative Aspergillus flavus with accession number LC424503. The gene coding for extracellular triacylglycerol lipase was isolated from Aspergillus flavus species, sequenced, and characterised using bioinformatics tools. An open reading frame of 420 amino acid sequence was obtained and designated as Aspergillus flavus lipase (AFL) sequence. Alignment of the amino acid sequence with other lipases revealed the presence GHSLG sequence which is the lipase consensus sequence Gly-X1-Ser-X2-Gly indicating that it a classical lipase. A catalytic active site lid domain composed of TYITDTIIDLS amino acids sequence was also revealed. This lid protects the active site, control the catalytic activity and substrate selectivity in lipases. The 3-Dimensional structural model shared 34.08% sequence identity with a lipase from Yarrowia lipolytica covering 272 amino acid residues of the template model. A search of the lipase engineering database using AFL sequence revealed that it belongs to the class GX-lipase, superfamily abH23 and homologous family abH23.02, molecular weight and isoelectric point values of 46.95鈥塊Da and 5.7, respectively. N-glycosylation sites were predicted at residues 164, 236 and 333, with potentials of 0.7250, 0.7037 and 0.7048, respectively. O-glycosylation sites were predicted at residues 355, 358, 360 and 366. A signal sequence of 37 amino acids was revealed at the N-terminal of the polypeptide. This is a short peptide sequence that marks a protein for transport across the cell membrane and indicates that AFL is an extracellular lipase. The findings on the structural and molecular properties of Aspergillus flavus lipase in this work will be crucial in future studies aiming at engineering the enzyme for biotechnology applications

    Conservation agriculture affects grain and nutrient yields of Maize (Zea Mays L.) and can impact food and nutrition security in Sub-Saharan Africa

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    Maize is a major staple and plays an essential role in food and nutrition security in Sub-Saharan Africa (SSA). Conservation agriculture (CA), a climate-smart agriculture practise based on minimum soil disturbance, crop residue retention, and crop diversification, has been widely advocated but without extensive research on the impact it may have on maize nutrient composition, and food and nutrition security. This study assessed the grain yield, macro- and micronutrient mineral content, and nutrient yield of eight maize varieties grown in Malawi, and how these are affected by CA practises over two seasons. The minerals were analysed by inductively coupled plasma (ICP) coupled to optical emission spectroscopy (OES) and to mass spectroscopy (MS). Grain yield and Se content differed among the varieties, while C, N, Fe, K, Mg, Mn, P, and Zn were similar. The local variety Kanjerenjere showed lowest grain and nutrient yields. The open-pollinated varieties (OPVs) concentrated more minerals than the F1 hybrids, but the latter showed higher yields for both grain and nutrients. Typical consumption of the eight maize varieties could fully meet the protein and Mg dietary reference intake (DRIs) of Malawian children (1鈥3 years), as well as Mg and Mn needs of adult women (19鈥50 years), but their contribution to dietary requirements was low for Fe (39鈥41%) and K (13鈥21%). The trials showed that CA increased grain yield (1.2- to 1.8-fold) and Se content (1.1- to 1.7-fold), but that it had no effect on C, K, Mg, P, and Zn, and that N (1.1- to 1.2-fold), Mn (1.1- to 1.8-fold), and Fe (1.3- to 3.4-fold) were reduced. The high increase in grain yield under CA treatments resulted in increased yields of protein and Se, no effect on the yields of K, Mg, Mn, P, Zn, and reduced Fe yield. Conservation agriculture could contribute in reducing the risk of Se deficiency in Malawian women and children but exacerbates the risk of Fe deficiency. A combination of strategies will be needed to mitigate some of the foreseen effects of climate change on agriculture, and food and nutrition security, and improve nutrient intake
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