5-86: Production of hemicellulolytic enzymes by a thermophilic Aspergillus strain isolated from sugarcane bagasse

Degradation of lignocellulosic biomass by microbial enzymes has emerged as an important technology to obtain many products of industrial interest, among which bioethanol stands out. In Brazil, sugarcane bagasse represents an attractive material for this process, being an agro-industrial waste widely available. The production of hemicellulolytic enzymes able to efficiently degrade sugarcane bagasse, aiming to obtain fermentable sugars for ethanol production, is the focus of this work. The strain Aspergillus M 7.3, isolated from piles of sugarcane bagasse, was initially cultivated in a mixture of sugarcane bagasse and wheat bran (1:1 w/w), at 45oC, for up to 336h. The production of cellulase (FPase) and xylanase were evaluated, which yielded peaks at 48 h (1.0 U/g) and 192 h (1239 U/g), respectively. Afterwards, other agricultural wastes were evaluated as substrates to cultivate the fungus. Higher xylanase productions were obtained using mixtures (9:1 w/w) of corn straw and wheat bran (4944 U/g at 192 h) and corn straw and barley (4080 U/g at 240 h). The microorganism cultivation in a mixture of corn straw and wheat bran (9:1 w/w) provided a CMCase production of 43.4 U/g (192 h) and the highest beta-glucosidase production was observed during cultivation in wheat bran (26 U/g at 336 h). The results indicate that Aspergillus M 7.3 is a promising strain concerning the production of enzymes for sugarcane bagasse hydrolysis. Thus, its enzymes will be subsequently physical-chemically characterized and tested concerning their bagasse hydrolysis performance.
 Key words: Aspergillus, cellulases, xylanase, sugarcane bagasse, agricultural residues
Financial support: FAPESP and CNPq.