A low-molecular-weight xylanase activity (XynI) was isolated from the fungus Acrophialophora nainiana after growth in a solid medium containing wheat bran. XynI was purified to apparent homogeneity by ultrafiltration and gel filtration chromatography. The purified enzyme had a molecular weight value of approx. 17 kDa, as determined by SDS-PAGE. This enzyme was most active at 50 degreesC and pH 6.0. At 50 degreesC the half-life was 150 min. The apparent Km value for birchwood xylan was much lower than the Km value for oat spelt xylan. XynI was activated by L-cysteine, DTE, beta-mercaptoethanol, and L-tryptophan. XynI did not show significant sequence homology with other xylanases. The analysis of hydrolysis products of xylans and wood pulps showed that XynI was able to release xylooligomers ranging from X2 to X3 and X2 to X6, respectively. The enzyme was not active against acetylated xylan. A small amount of xylose was released from deacetylated, birchwood, and oat spelt xylans. The results obtained with enzymatic treatment of Kraft pulp indicated a reduction in the amount of chlorine compounds required for the process and enhanced brightness gain.

Most Eucalyptus plantations in Brazil aim the production of paper and charcoal, but the use of the species for lumbering, construction and extraction of essential oil has increased. Eleven species of Eucalyptus were assessed in regard to their essential oil production potential, nine never used before for commercial, essential oil extraction. Assessements were compared with Eucalyptus citriodora and Eucalyptus globulus, already explored in oil production for perfume and medical purposes, aiming to increase the availability of commercial species and the relationship between oil production and climatic conditions. Eucalyptus leaves were seasonally sampled (three months interval) for distillation and determination of productivity and chemical composition of oil -contents of oils main components. Eucalyptus viminalis showed the highest potential for cineol, and standed out among the species not yet used commercially. Influenced by soil moisture contents and air temperature, the lowest and the highest oil production happened respectively in Spring and Summer. Water deficiency in Spring caused the lowest oil production. In the Summer, on the other hand, the highest oil production was observed when temperatures were higher and no water deficiency registered. There was no climatic influence on the main oil chemical component. Key words: Eucalyptus spp., essential oil, yield, climatic influence POTENCIAL DE ONZE ESPÉCIES DE EUCALIPTO PARA A PRODUÇÃO DE ÓLEOS ESSENCIAISRESUMO: A maioria das plantações de Eucalyptus brasileiras tem como objetivo a produção de papel e carvão, mas o uso das espécies para madeira, construção e extração de óleo essencial tem aumentado. Neste trabalho foram estudadas onze espécies de eucalipto quanto ao potencial para a obtenção de óleo essencial. Entre as espécies estudadas, nove não têm sido utilizadas na obtenção comercial de óleo. Para efeito comparativo, avaliou-se também duas outras espécies, o Eucalyptus citriodora e o Eucalyptus globulus, as quais são amplamente utilizadas, respectivamente, para a obtenção de óleo aromatizante e óleo para fins medicinais. Os objetivos do estudo foram ampliar o leque de materiais disponibilizados para os produtores de óleo essencial e correlacionar o rendimento de óleo com as variações climáticas existentes ao longo do ano. Foram realizadas coletas sazonais (cada 3 meses) de folhas para a destilação e determinação do rendimento e avaliação da composição química do óleo. Dentre as espécies ainda não utilizadas comercialmente, considerando-se o rendimento do óleo e os teores dos componentes principais, o Eucalyptus viminalis revelou-se aqueal de maior potencial para a exploração de óleo essencial rico em cineol, para uso medicinal. O menor e o maior rendimento de óleo foram obtidos, respectivamente, na primavera e no verão. A disponibilidade de água no solo e a temperatura do ar influenciaram o rendimento de óleo. Sob condições de deficiência hídrica, observada na primavera, ocorreu o menor rendimento de óleo. No verão, quando a temperatura foi m...

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