Influência da agitação e da aeração na produção da enzima alfa-acetolactato descarboxilase (ALDC) de Bacillus subtilis por cultivo submerso visando escalonamento

Abstract

One of the intermediates produced in the alcoholic fermentation process during brewing is diacetyl which, even at concentrations as low as 0.15 ppm, carries an undesirable organoleptic characteristic to various styles of beer, the buttery flavor. The diacetyl rest, a process of removal of this compound that lasts from 2 to 4 weeks, is a limiting step in beer maturation, becoming time consuming in production and capital consuming for the storage of the product. The enzyme alpha-acetolactate decarboxylase (ALDC) avoids the formation of diacetyl. An experimental design was applied to evaluate the influence of agitation and aeration, in a laboratory scale, over the production of the enzyme ALDC of Bacillus subtilis ICA56 by submerged culture. Production of ALDC enzyme in a bioreactor for 14h culture at 37°C, with different combinations of stirring rates (150 rpm, 300 rpm and 450 rpm) and aeration rates (0 L/min, 0.5 L/min and 1 L/min). The highest activity (0,86 ± 0.036 U/mL) was obtained at an aeration rate of 0,5 L/min and a stirring rate of 300 rpm. To evaluate the enzymatic activity, a colorimetric methodology was used and response surface methodology was used to evaluate the influence of the factors in the analyzed response. From the results of the present investigation, it can be concluded that the quadratic variable of the agitation has a significant effect on the production of ALDC of B. subtilis. The effects of the variable aeration and the interaction between both variables were not significant. A positive effect was observed, upon increasing the stirring rate, on the production of B. subtilis’ total proteins. Further studies are required in order to predict optimal conditions of agitation and aeration for the analyzed response.