Monday, May 4, 2009
5-39
Characterization of cellulases and hemicellulases produced by Thermoascus aurantiacus in hydrolysis experiments
Joseana R. Monte1, Michel Brienzo1, and Adriane Milagres2. (1) Biotechnology, Engineering School of Lorena, Estrada do Campinho S/N, Lorena, Brazil, (2) Biotechnology, Escola de Engenharia de Lorena EEL/USP, Estrada Municipal do Campinho, s/n, Lorena, 12600-970, Brazil
Cellulase and hemicellulase enzymes were produced by Thermoascus aurantiacus on sugar cane bagasse, sugar cane straw, wheat straw and corn stover. The enzymes produced were characterized by protein and various enzyme activity measurements. On sugar cane straw and sugar cane bagasse higher cellulolytic enzyme activities were reached, while the activities obtained on wheat straw and corn stover were considerably lower. Elevated levels of endoglucanase and b-glucosidase activities were produced simultaneously and both enzymes exhibited significant thermostability, with half-lives of 42 and 18 min, respectively, at 80 C. The produced and two commercial cellulases (Celluclast 1.5 L and novozymes) were also characterized in hydrolysis experiments. They were dosed on the basis of filter paper activity in order to ensure constant enzyme/substrate ratio in all experiments. Sugarcane bagasse was treated with hydrogen peroxide in an alkaline media in different conditions: temperature (20 and 60°C ), hydrogen peroxide concentration (2 and 6 % w/v), reaction time (4 and 16 h) and magnesium sulfate concentration (0 and 0.5 % w/w). The results showed that at the best condition it was recovered more than 96 % of the original polysaccharide and also separated more than 88% of lignin. On bagasse pulp obtained from alkaline peroxide process composed of 5.9% lignin, 61% cellulose and 16% hemicellulose, the performance of commercial enzyme was 63%. As a result, our experiments demonstrated that sugarcane bagasse is a good substrate both for enzyme production and hydrolysis, since high cellulolytic activities could be reached using it as carbon source.