Cellulases are widely applied in textile finishing, such as for the removal of protruding surface fibrils to reduce pilling propensity and to achieve the worn-out look in denim garments. The main drawback of enzymatic denim processing is the back-staining of indigo, which reduces the desired blue-white contrast. Alongside an accurate selection of the type of cellulase or vigorous post-washing of the garments, the simultaneous application of auxiliaries in the enzymatic treatment may help to reduce backstaining and improve cellulase efficiency. In the present work, the influence of additives such as surfactants and dispersing agents on indigo adsorption and on the treatment of an undyed cotton fabric with Hypocrea jecorina cellulases was investigated. Indigo adsorption was successfully reduced by more than 75% with ethoxylated nonionic surfactants at concentrations below 0.2 g l À1 . The weight loss of cotton fabrics after 120 min treatment was significantly increased with nonionic surfactants and polyvinylpyrrolidone. It could be further shown that protein adsorption on the cotton fabric decreased with the increasing concentration of the additives, while the nonionic surfactants were more efficient than the polyvinylpyrrolidone. Adsorption of a complete cellulase mixture was affected differently by the surfactants than by an exoglucanase-free endoglucanase-rich preparation.
Neste trabalho simulou-se a desnitrificação via nitrito em lixiviado de aterro sanitário, operando-se em escala laboratorial através de um reator em batelada sequencial (RBS) adicionando-se melaço de cana como fonte externa alternativa de carbono. As razões DBOlixiviado+melaço/N-NOx estudadas foram 0,37; 4; 12 e 14 com tempo de reação anóxica de 4,33 h (DBO/N-NOx=0,37; 4 e 14) e 22 h (DBO/N-NOx=12). A taxa específica de desnitritação foi de 0,07 kg nitrito.kg-1 sólidos suspensos voláteis (SSV)*dia após 4,33 h de reação anóxica nos ensaios sem adição de melaço de cana e 0,19 e 0,12 kg nitrito.kg-1 SSV*dia nos ensaios realizados com adição de melaço de cana, fornecendo uma razão DBO/N-NOx de 4 e 14, respectivamente. Ampliando-se o tempo de reação anóxica para 22 h e realizando os ensaios sob razão DBO/N-NOx de 12, a taxa específica de desnitritação foi aumentada para 0,55 kg nitrito.kg-1 SSV*dia.
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