Resumo

Aspergillus is among the main genera for the Biotechnology industry, whereas black aspergilli are noted for the variety of compounds they produce, from organic acids to enzymes like amylases and celobiohydrolases. In this work, a new isolate, which has shown potential as cellulase producer, was studied, to determine the best conditions for growth and sporulation, and to evaluate its dynamic of enzyme production on different substrates. An amount of 50 conidia of the black Aspergillus sp. A1257 was inoculated onto slants of Czapek, Vogel Minimal Medium (MMV), potato dextrose (PDA) and yeast extract glucose (YAG) agars. Growth and sporulation were evaluated for 21 days at room temperature and 30ºC. Growth was also determined in media supplemented with glucose, starch, carboximetilcellulose, glycerol, soy and olive oils. Enzyme activities were determined for 7 days by revealing the zone of substrate degradation in solid media, and expressed as enzyme ratios (ER = enzyme activity zone/ colony diameter). All experiments were done in triplicate. Strain A1257 grew better and presented intense sporulation (7 days) when cultivated in PDA at room temperature. However, A1257 modified its growth profile at 30ºC. In this temperature, growth was sharply faster and higher in YAG slants, while sporulation was still more intense in PDA. Among the carbon sources offered, glycerol yielded the highest growth. Cellulase activity (ER^cel = 1.0) was induced quite early (2 days) for a culture which started from conidia, and kept a similar ratio for 7 days. The same was observed for the lipase activity, which reached a similar ER^am (0.9) after 2 days. On the contrary, A1257 produced low amylase activity (ER^am = 0.3; 2 days) at the initial times. Results showed the best condition for growth and sporulation of A1257, and this information will be further utilized to improve inoculum formation and fermentative processes with this fungus. It was also shown that this strain may not be used as a fermentation agent for amylase production, whereas the early detection of good cellulase activity encourages the optimization of this enzyme complex by A1257. According to the results, the production of lipase by A1257 is also a good perspective. Thus, we conclude that A1257 is a promising strain to develop new processes of enzyme production.