XYLANASE PRODUCTION BY ASPERGILLUS VERSICOLOR

The xylanolytic system of Aspergillus versicolor is controlled by indu ction and carbon catabolite repression. Carboxymethylcellulose and whe at bran were the best inducers of xylanolytic activity. When the fungu s was grown for 5 days on VOGEL's liquid medium with wheat bran, the o ptimal pH and temperature for xylanase production were 6.5 and 30 degr ees C, respectively. Optimal conditions for the xylanolytic activity a ssay were at pH 6.0 and 55 degrees C. The half-life at 60 degrees C of the crude enzyme was 6.5 and 21 minutes, in the absence or presence o f substrate, respectively. Xylan is the main hemicellulosic component of plant biomass being present in appreciable quantities in agricultur al and several agroindustrial wastes. From the products of xylan enzym atic hydrolysis it is possible to obtain cell protein, fuels and other chemicals. Xylanases combined with cellulase could have applications in food processing. Cellulase-free xylanases can be also utilized for preparation of cellulose pulps and liberation of textile fibres (WOODW ARD 1984; BIELY 1985, WONG et al. 1988). In view of the potential appl ications of xylanases, a study of these enzymes from various sources a nd their multiplicity is desirable. Among xylanolytic microorganisms, filamentous fungi have been more extensively studied and the genus Asp ergillus has been shown to be an efficient producer of xylanases. Prel iminary observations from our laboratory have demonstrated that a stra in of Aspergillus versicolor, isolated from Brazilian soil, produced h igh xylanase and low cellulase levels, which is an interesting charact eristic for some industrial applications. In this report we describe t he production and some properties of xylanase obtained from this fungu s.