Avaliação da termoestabilidade e das condições de extração das amilases produzidas por aspergillus sp. fsde16 em bagaço de malte

Abstract

The Brazilian agricultural production generates a large amount of waste, therefore its correct reutilization is a great challenge currently faced by agro-industries. Among the agro-industrial waste, it is included the malt bagasse, which is a by-product generated by beer brewing processes. One of the ways to reuse agro-industrial waste is by utilizing it as a substrate to grow microorganisms with the goal of producing bio-products of economic interest by solid-state fermentation. An example of these bio-products are the amylases, a group of enzymes that act synergistically to hydrolyze starch molecules and are utilized by several types of industries. In the face of this, this study has the goal of evaluating the thermostability and the conditions for extraction of amylases produced by Aspergillus sp. FSDE16 in a medium composed by malt bagasse humidified with a solution of salts. Thermostability evaluation was carried by incubating the enzyme extract at 30 oC, 50 oC and 70 oC during 8 hours, and by monitoring its activity during the process. While the optimum conditions of extraction were obtained from an experimental factorial design 23 with 3 center points. This design evaluated the effects of agitation speed (100, 150 and 200 rpm), extraction time (20, 40 and 60 minutes), and solvent/sample ratio (10, 20 and 30 mL/g) on the activity per mass of medium (U/g) and on the activity per volume of extract (U/mL). The results showed that the thermostability of the amylases is compromised by temperature increase, and that after 8 hours of incubation the relative activities at 30 oC, 50 oC and 70 oC were equal to 117.6%, 78.7% and 24.6%, respectively. In regard to the conditions of extraction, it was observed that the best experiments for activity in U/g unit were the numbers 6 (100 rpm, 60 minutes and 30 mL/g) and 5 (200 rpm, 60 minutes and 30 mL/g), whose activities were equal to 11.43 ± 0.49 U/g and 10.86 ± 0.22 U/g, respectively. While for the activity in U/mL unit, the best experiments were the numbers 10 (150 rpm, 40 minutes and 20 mL/g), 8 (200 rpm, 60 minutes and 10 mL/g) and 2 (200 rpm, 20 minutes and 10 mL/g), whose activities were equal to 0.499 ± 0.011 U/mL, 0.497 ± 0.055 U/mL and 0.487 ± 0.080 U/mL, respectively.