418 resultados para thermophilic microorganism

em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"


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The alkalophilic bacteria Bacillus licheniformis 77-2 produces significant quantities of thermostable cellulase-free xylanases. The crude xylanase was purified to apparent homogeneity by gel filtration (G-75) and ionic exchange chromatography (carboxymethyl sephadex, Q sepharose, and Mono Q), resulting in the isolation of two xylanases. The molecular masses of the enzymes were estimated to be 17 kDa (X-I) and 40 kDa (X-II), as determined by SDS-PAGE. The K(m) and V(max) values were 1.8 mg/mL and 7.05 U/mg protein (X-I), and 1.05 mg/mL and 9.1 U/mg protein (X-II). The xylanases demonstrated optimum activity at pH 7.0 and 8.0-10.0 for xylanase X-I and X-II, respectively, and, retained more than 75% of hydrolytic activity up to pH 11.0. The purified enzymes were most active at 70 and 75 degrees C for X-I and X-II, respectively, and, retained more than 90% of hydrolytic activity after 1 h of heating at 50 degrees C and 60 degrees C for X-I and X-II, respectively. The predominant products of xylan hydrolysates indicated that these enzymes were endoxylanases.

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A comparative study was carried out to evaluate protease production in solid-state fermentation (SSF) and submerged fermentation (SmF) by nine different thermophilic fungi - Thermoascus aurantiacus Miehe, Thermomyces lanuginosus, T. lanuginosus TO.03, Aspergillus flavus 1.2, Aspergillus sp. 13.33, Aspergillus sp. 13.34, Aspergillus sp. 13.35, Rhizomucor pusillus 13.36 and Rhizomucor sp. 13.37 - using substrates containing proteins to induce enzyme secretion. Soybean extract (soybean milk), soybean flour, milk powder, rice, and wheat bran were tested. The most satisfactory results were obtained when using wheat bran in SSF. The fungi that stood out in SSF were T. lanuginosus, T. lanuginosus TO.03, Aspergillus sp. 13.34, Aspergillus sp. 13.35, and Rhizomucor sp. 13.37, and those in SmF were T. aurantiacus, T. lanuginosus TO.03, and 13.37. In both fermentation systems, A. flavus 1.2 and R. pusillus 13.36 presented the lowest levels of proteolytic activity.

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Proteases are one of the most important groups of industrial enzymes, with considerable application in the food industry. The aim of this work was to study a novel protease produced by the thermophilic fungus, Thermoascus aurantiacus, through solid-state fermentation (SSF). The enzyme acted optimally at pH 5.5 and 60 degrees C it was stable up to 60 degrees C for 1 h and in the pH range 3.0-9.5. To elucidate the enzyme's proteolytic activity, its hydrolytic profile on bovine casein, an important protein in the food industry, was studied by enzymatic hydrolysis on skim milk, analyzed by gel electrophoresis (UREA-PAGE), which clearly showed that the protease does not have the same specificity as bovine chymosin. (c) 2006 Elsevier Ltd. All rights reserved.

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The thermophilic fungus Thermoascus aurantiacus 179-5 and the mesophilic Aureobasidium pullulans ER-16 were cultivated in corn-cob by solid state fermentation for P-glucosidase production. After fermentation both enzymes were purified. The beta-glucosidases produced by the strains A. pullulans and T aurantiacus were most active at pH 4.0-4.5 and 4.5, with apparent optimum temperatures at 80 and 75 degrees C, respectively. Surprisingly, the enzyme produced by the mesophilic A. pullulans was stable over a wider range of pH (4.5-9.5 against 4.5-6.5) and more thermostable (98% after 1 h at 75 degrees C against 98% after 1 h at 70 degrees C) than the enzyme from the thermophilic T. aurantiacus. The t((1/2)) at 80 degrees C were 90 and 30 min for A. pullulans and T. aurantiacus, respectively. beta-Glucosidase thermoinactivation followed first-order kinetics and the energies of denaturation were 414 and 537 kJ mol(-1) for T. aurantiacus and A. pullulans, respectively. The result showed that beta-glucosidase obtained from the mesophilic A. pullulans is more stable than that obtained from the thermophilic T. aurantiacus. (C) 2007 Elsevier Ltd. All rights reserved.

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