In this study we determined some properties of the cholesterol oxidase from a Brevibacterium strain isolated from buffalos milk and identified the cholesterol degradation products by the bacterial cell. A small fraction of the enzyme synthesized by cells cultured in liquid medium for 7days was released into the medium whereas a larger fraction remained bound to the cell membrane. The extraction of this fraction was efficiently accomplished in 1 mM phosphate buffer, pH 7.0, containing 0.7% Triton X-100. The enzyme stability under freezing and at 45 o C was improved by addition of 20% glycerol. The optimum temperature and pH for the enzyme activity were 53°C and 7.5, respectively. The only steroidal product from cholesterol oxidation by the microbial cell and by the crude extract of the membrane-bound enzyme was 4-colesten-3-one. Chromatographic analysis showed that minor no steroidal compounds as well as 4-colesten-3-one found in the reaction media arose during fermentation process and were extracted together with the enzyme in the buffer solution. Cholesterol oxidation by the membrane-bound enzyme was a first order reaction type.

Avaliou-se a produção de celulases e xilanase de Aspergillus niger IZ-9, crescido sobre bagaço de cana, quimicamente tratado, como substrato. Os tratamentos foram: solução de hidróxido de sódio a 4%, e solução de hidróxido de sódio a 4%, ácido fosfórico p.a. e vapor. A produção das enzimas celulolíticas (celulase total, endoglicanase e -glicosidase) e xilanase foi observada nos bagaços tratados e não-tratado. O tratamento com solução de hidróxido de sódio a 4% promoveu maior indução de síntese da maioria das enzimas, com exceção de -glicosidase, a qual apresentou produção semelhante para os bagaços tratados quimicamente.

No abstract

Bamboo carbohydrates were hydrolyzed with commercial amylases and a mixture of fungal culture broths containing cellulolytic and hemicellulolytic enzymes. The effects of cooking temperature and the size of fiber particles were also investigated. It was found that the higher the cooking temperature, the higher the rate of sugar formation and the lower the viscosity of the slurry. Additions of cellulose and hemicellulose digesting enzymes increased the sugar yield and decreased the viscosity of both the cooked and noncooked slurries. A smaller size of particle appeared to favor the average saccharification rate. Although glucose, xylose, and cellobiose were present in the hydrolysates, only 50% of the total carbohydrate was digested, and 78.9% of this was converted to reducing sugars. The alcohol efficiency for the fermentation of cooked and noncooked mashes by Saccharomyces was about 85%.