Aplicação da alfa-acetolactato descarboxilase (ALDC) isolada de Bacillus subtilis ICA 56 para o desenvolvimento de processos industriais em cervejas.

Abstract

During the brewing process, some compounds are formed in the primary fermentation and may interfere in the quality of the final product; these compounds are named off flavors. Diacetyl is one undesirable off flavor in beer. For diacetyl removal, alpha acetolactate decarboxylase (ALDC) can de used because it prevents the formation of diacetyl in beer by converting acetolacte directly into acetoin. In this context, the objective of this work was to evaluate the reduction of diacetyl in the brewing process using ALDC produced by Bacillus subtilis ICA 56. Therfore, this research was divided in two stages. The first was intended to apply the produced free enzyme, evaluating its ability to reduce maturation time in beer. For this, 10 L of beer were produced and the enzyme was inserted in the fermentation stage; maturation was then started, and each day, an 8 mL aliquot was taken (for 8 days) and then NaCl was added for analysis of the samples using mass detector gas chromatography (GC-MS) employing the micro extraction phase solid technique (SPME). The second step was to immobilize and evaluate the pH and temperature stability parameters of ALDC, using diethylaminoethyl agarose (DEAE), monoaminoethyl N-ethyl agarose (MANAE) or MANAE-glutaraldehyde as supports. The stability of these biocatalysts after trehalose and glutaraldehyde coating was also evaluated. From the obtained results it is possible to see that maturation time was shorten by the enzyme, in the presence of free ALDC, diacetyl was eliminated on the sixth day of maturation, while in beer without enzyme addition, it was still present on the eighth day of maturation. Regarding immobilization and stability, the best activities were obtained when ALDC was immobilized in DEAE, covered with treaose and MANAE-glutaraldehyde, also after treatment with trehalose, reaching activities of 1.46 U/g and 1.62 U/g support, respectively. The pH and temperature that allowed the highest activity and stability were 6.0 and 45 °C, respectively, while the enzyme was rapidly inactivated at pH 9 and 10. MANAE-glutaraldehyde support offered the best activity values and was the most stable.