1,520 research outputs found

    Production of xylanolytic enzymes by Aspergillus terricola in stirred tank and airlift tower loop bioreactors

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    Fungi producing high xylanase levels have attracted considerable attention because of their potential industrial applications. Batch cultivations of Aspergillus terricola fungus were evaluated in stirred tank and airlift bioreactors, by using wheat bran particles suspended in the cultivation medium as substrate for xylanase and b-xylosidase production. In the stirred tank bioreactor, in physical conditions of 30°C, 300 rpm, and aeration of 1 vvm (1 l/min), with direct inoculation of fungal spores, 7,475 U/l xylanase was obtained after 36 h of operation, remaining constant after 24 h. In the absence of air injection in the stirred tank reactor, limited xylanase production was observed (final concentration 740 U/l). When the fermentation process was realized in the airlift bioreactor, xylanase production was higher than that observed in the stirred tank bioreactor, being 9,265 U/l at 0.07 vvm (0.4 l/min) and 12,845 U/l at 0.17 vvm (1 l/min) aeration rate.Fundação para a Ciência e a Tecnologia (FCT)CNPq (Brasil)FAPESP (Brasil

    A new strategy for xylanase production using wheat straw autohydrolysis liquor as substrate

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    Agro-industrial residues are lignocellulosic materials with a high content of cellulose, hemicellulose and lignin. If such residues can be produced in bioprocesses (e.g. xylanase production) there is an attractive possibility of their integral use in biotechnological processes. In general, xylanase biosynthesis is induced by its substrate – xylan, but the high xylan content of some wastes such as corn cobs and wheat bran makes them an accessible and cheap source of inducers. Another alternative to improve the xylanase production, which is the main goal of this work, is the treatment of lignocellulosic materials in autohydrolysis processes which, under optimized conditions, lead to the solubilization of hemicelluloses (liquid phase, liquor) that may be favorable to xylanase production. The inclusion of these components in the nutrient medium composition can be a strategy to optimize the microbial xylanase biosynthesis. The best conditions for xylanase production were observed when the microorganism was cultivated in birchwood xylan for 6 days; however, satisfactory results were obtained using a combination of 1% wheat bran with 2% or 10% autohydrolysis liquor, for 5 days fermentation, once the xylanase production was around 86-87% of production with xylan. Besides, the obtained production with 100% wheat straw autohydrolysis liquor was also interesting, once after 7 days of cultivation, the xylanase production was higher than the ones obtained with wheat bran or by the combination of wheat bran and liquor.Biota FAPESP (Brazil)Fundação para a Ciência e a Tecnologia (FCT

    Application of wheat straw autohydrolysis liquor to xylanase and β-xylosidase large-scale production in a stirred tank bioreactor

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    Research into microbial xylanases production has increased due to its several applications. In this context, studies that make this practice feasible are important. Wheat bran is an inexpensive byproduct, which contains around 28% hemicellulose; however, the wheat bran particles suspended in the cultivation medium have to be decomposed to soluble compounds to be used by the fungi and the treatment of lignocellulosic materials in autohydrolysis processes makes this easier. The inclusion of these treated materials in the nutrient media can be a strategy to increase and undervalue xylanase production. The best conditions for xylanase and β-xylosidase production were observed when A. ochraceus was cultivated with 1% wheat bran added 10% wheat straw autohydrolysis liquor as carbon source, this substrate was more favorable when compared with xylan, wheat bran and wheat straw autohydrolysis liquor used separately. The application of this substrate in a stirred tank bioreactor shows the need for improvements of the fermentation process

    Production of xylanase and β-xylosidase from autohydrolysis liquor of corncob using two fungal strains

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    Agroindustrial residues are materials often rich in cellulose and hemicellulose. The use of these substrates for the microbial production of enzymes of industrial interest is mainly due to their high availability associated with their low cost. In this work, corncob (CCs) particles decomposed to soluble compounds (liquor) were incorporated in the microbial growth medium through autohydrolysis, as a strategy to increase and undervalue xylanase and b-xylosidase production by Aspergillus terricola and Aspergillus ochraceus. The CCs autohydrolysis liquor produced at 200 C for 5, 15, 30 or 50 min was used as the sole carbon source or associated with untreated CC. The best condition for enzyme synthesis was observed with CCs submitted to 30 min of autohydrolysis. The enzymatic production with untreated CCs plus CC liquor was higher than with birchwood xylan for both microorganisms. A. terricola produced 750 total U of xylanase (144 h cultivation) and 30 total U of b-xylosidase (96–168 h) with 0.75% untreated CCs and 6% CCs liquor, against 650 total U of xylanase and 2 total U of b-xylosidase in xylan; A. ochraceus produced 605 total U of xylanase and 56 total U of b-xylosidase (168 h cultivation) with 1% untreated CCs and 10% CCs liquor against 400 total U of xylanase and 38 total U of b-xylosidase in xylan. These results indicate that the treatment of agroindustrial wastes through autohydrolysis can be a viable strategy in the production of high levels of xylanolytic enzymes.This work was supported by State of Sao Paulo Research Foundation (FAPESP/Brazil), National Counsel of Technological and Scientific Development (CNPq/Brazil), National System for Research on Biodiversity (SISBIOTA-Brazil, CNPq 563260/2010-6/FAPESP 2010/52322-3), and Portuguese Foundation for Science and Technology (FCT/Portugal). Hector A. Ruiz thanks to Mexican Science and Technology Council (CONACYT, Mexico) for PhD fellowship support (CONACYT grant number: 213592/308679)

    The actin-myosin regulatory MRCK kinases: regulation, biological functions and associations with human cancer

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    The contractile actin-myosin cytoskeleton provides much of the force required for numerous cellular activities such as motility, adhesion, cytokinesis and changes in morphology. Key elements that respond to various signal pathways are the myosin II regulatory light chains (MLC), which participate in actin-myosin contraction by modulating the ATPase activity and consequent contractile force generation mediated by myosin heavy chain heads. Considerable effort has focussed on the role of MLC kinases, and yet the contributions of the myotonic dystrophy-related Cdc42-binding kinases (MRCK) proteins in MLC phosphorylation and cytoskeleton regulation have not been well characterized. In contrast to the closely related ROCK1 and ROCK2 kinases that are regulated by the RhoA and RhoC GTPases, there is relatively little information about the CDC42-regulated MRCKα, MRCKβ and MRCKγ members of the AGC (PKA, PKG and PKC) kinase family. As well as differences in upstream activation pathways, MRCK and ROCK kinases apparently differ in the way that they spatially regulate MLC phosphorylation, which ultimately affects their influence on the organization and dynamics of the actin-myosin cytoskeleton. In this review, we will summarize the MRCK protein structures, expression patterns, small molecule inhibitors, biological functions and associations with human diseases such as cancer

    Quasar accretion disk sizes from continuum reverberation mapping in the DES standard-star fields

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    Measurements of the physical properties of accretion disks in active galactic nuclei are important for better understanding the growth and evolution of supermassive black holes. We present the accretion disk sizes of 22 quasars from continuum reverberation mapping with data from the Dark Energy Survey (DES) standard star fields and the supernova C fields. We construct continuum lightcurves with the \textit{griz} photometry that span five seasons of DES observations. These data sample the time variability of the quasars with a cadence as short as one day, which corresponds to a rest frame cadence that is a factor of a few higher than most previous work. We derive time lags between bands with both JAVELIN and the interpolated cross-correlation function method, and fit for accretion disk sizes using the JAVELIN Thin Disk model. These new measurements include disks around black holes with masses as small as 107\sim10^7 MM_{\odot}, which have equivalent sizes at 2500\AA \, as small as 0.1\sim 0.1 light days in the rest frame. We find that most objects have accretion disk sizes consistent with the prediction of the standard thin disk model when we take disk variability into account. We have also simulated the expected yield of accretion disk measurements under various observational scenarios for the Large Synoptic Survey Telescope Deep Drilling Fields. We find that the number of disk measurements would increase significantly if the default cadence is changed from three days to two days or one day.Comment: 33 pages, 24 figure

    Quercetin-loaded lecithin/chitosan nanoparticles: physicochemical characterization

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    Quercetin is an abundant flavonoid in food plants and has been extensively investigated for its pharmacological effects that include anti-tumor, anti-inflammatory, antioxidant, and hepatoprotective activities. Being sparingly soluble in water and subject to degradation in aqueous intestinal fluids, the absorption of quercetin is limited upon oral administration. The aim of this study was to encapsulate quercetin on lecithin/chitosan nanoparticles by auto-assembled technique for improvement its solubility, stability and oral bioavailability. The nanoparticles were obtained injecting a solution of lecithin (2.0 mg.mL-1) and quercetin (70 µg.mL-1) in ethanol (99%) into a chitosan (0.1 mg.mL-1) aqueous solution (pH 3.0), under mechanic stirring. The nanoparticles were characterized by measuring particle size, zeta potential and encapsulation efficiency. The morphology of nanoparticles was evaluated by transmission electron microscopy. Antioxidant activity of nanoparticles and free quercetin was also evaluated using the scavenging of 1,1-diphenyl-2-picrylhydrazyl radical and anti-lipid peroxidation. The nanoparticles showed mean diameter of 168.58±20.94 nm, with polydispersity index of 0.26±0.02, zeta potential of +56.46±1.94 mV, and encapsulation efficiency of 96.13±0.44%. The nanoparticles showed spherical shape and an antioxidant activity more effective than free quercetin. This work demonstrated that the quercetin was successfully encapsulated suggesting that the lecithin/chitosan nanoparticles is a promising delivery system to enhance the oral absorption and water solubility of quercetin.info:eu-repo/semantics/publishedVersio
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