Desenvolvimento de um sistema automático de alimentação controlado pelo pH do meio para produção de celulases por Penicillium echinulatum S1M29 em regime descontínuo alimentado

Abstract

The production of cellulases is of major interest in order to increase economic viability of second generation ethanol. This complex contains three major enzymes: endoglucanases, exoglucanases and β-glucosidades. Filamentous fungi can be efficient cellulase producers, one of this microorganisms being Penicillium echinulatum. Cellulases are usually produced in submerged fermentation and different strategies can be adopted in order to increase productivity. Previous studies show that the addition of an inducer substrate in fed-batch can improve cellulase activities, so can the optimal pH. It has been reported for other fungi that when there is no pH control, the medium acidifies while cellulose is being consumed and the pH raises when there is lack of substrate, therefore, the pH of the medium can be used to control cellulose addition. In this project, an automatic feeding system controlled by the pH of the medium was developed to add cellulose in fed-batch submerged fermentation of Penicillium echinulatum S1M29. The system was developed using a universal controller Novus N1100 with a pH controlling system Rovitec DosaMini 100 and a timer connected to a cellulose cylindrical container. The results presented by this work demonstrate that the automatic feeding system controlled by the pH of the medium functioned properly and four different conditions could be tested, obtaining maximum enzymatic activities of 1.4 U.mL-1 (FPase), 11.5 U.mL-1 (endoglucanase), 5.1 U.mL-1exoglucanase), 5.1 U.mL-1 (β-glucosidase) and 25.8 U.mL-1 (xylanases). An inverse relation between cellulose concentration and medium pH was observed, indicating that the pH can be related to the fungus metabolism. The tested conditions did not allow multiple feedings to happen, and low pH values and cellulose concentration interfered negatively in enzymatic activities. New conditions need to be tested n order to increase the amount and frequency of cellulose addition. Controlling pH decrease should also be performed to improve enzymatic activities.