Resumo

Amylases are among the most important commercial enzymes. Although found in a variety of organisms, the industrial production occurs mainly by microbial fermentations. The objective of this work was to determine the optimum values of independent variables for amylase production by the Penicillium sp. T10.5 isolate. The software Statistica 7.0 was used to plan fermentations according to a central composite design (ccd) 2ⁿ with 3 variables and 2 levels: starch (1-3 g/l); yeast extract (1.5-3.5 g/l); pH (4-8). 8 fermentations (50 ml) combining the high and low values of each variable, 6 fermentations of axial points (α, -1.41 to +1.41) and 5 fermentations combining the central values of the variables were conducted at 30 ºC and 150 rpm for 60 h. Biomasses were separated by filtration and liophylized to determine the dry weight. Amylolitic activities (starch hydrolisis) were determined in culture filtrates. The highest biomass production (0.584 g) occurred in fermentation 10 which contained 3.68 g/l starch and the central values of yeast extract and pH. The highest amylolitic activities were produced in the central point fermentations (337.4 U . ml^-1+ . min^-1 ± 24.8 ). Statistical analysis (ANOVA) determined significant quadratic effects of all variables on amylolitic activity (R² = 0.98). Surface response methodology allowed to identify the range of starch (1.5-2.5 g/l), yeast extract (2-3.5 g/l) and pH (5-8) for highest responses of amylase production. Solution was given for maximum response of amylase production (379.9 U . ml^-1+ . min^-1) and critical values were 2.06 g/l starch; 2.58 g/l yeast extract; pH 5,9. Thus, by means of ccd and surface response methodology it was possible to determine the best conditions for amylase production by a new isolate of Penicillium sp. This work opened as perspective the conduction of a final fermentation with the critical values to validate the statistical model and to investigate the kinetics of the batch process.