Xylanases have largely been obtained from filamentous fungi and bacteria; few studies have investigated the production of this enzyme by yeasts. The aim of this study was to isolate yeasts from different sources, such as vegetables, cereal grains, fruits, and agro-industrial waste and to obtain yeasts capable of producing celulase-free xylanase. Samples were enriched using yeast malt broth, and yeasts were isolated on Wallerstein nutrient agar. In all, 119 yeast strains were isolated and evaluated in terms of their ability to degrade xylan, which was found in the medium by using agar degradation halos, the basis of this polysaccharide, and Congo red dye. Selected microorganisms were grown in complex medium and the enzymatic activities of endo-xylanase, β-xylosidase, carboxymetilcellulase, and filter paper cellulose were determined over 96 h of cultivation; the pH and biomass concentration were also evaluated. The yeast strain 18Y, which was isolated from chicory and later identified as Cryptococcus laurentii, showed the highest endo-xylanase activity (2.7 U.mL-1). This strain had the ability to produce xylanase with low levels of cellulase production (both CMCase [0.11 U.mL-1 ] and FPase [0.10 U.mL-1 ]). This result gives this strain great biotechnological potential since this enzyme can be used for industrial pulp and paper bleaching.
RESUMO -A endo β-1,4 xilanase, principal enzima do complexo xilanolítico, hidrolisa aleatoriamente ligações β-1,4 da cadeia de hemicelulose e o interesse no seu estudo vem sendo estimulado pela sua aplicação em rações animais e no branqueamento de papel. Diante da importância da aplicação das xilanases é importante avaliar condições que aumentem a produção dessas enzimas a fim de tornar sua utilização comercial menos restrita. Neste trabalho foi realizada a produção de endo xilanase utilizando a levedura Cryptococcus laurentii. Cultivos submersos foram realizados, avaliando os componentes do meio de cultivo, através do uso de planejamento experimental fracionário, visando uma maior atividade da enzima. Os cultivos foram mantidos a 30°C, 150 rpm por 96 horas. A produção inicial foi de 3,4 U/mL, sendo que esta, após os experimentos, teve um incremento cerca de 60 %, onde a atividade máxima foi de 5,5 U/mL. Área temática: Processos Biotecnológicos
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