Thermostable crude endoglucanase produced by Aspergillus fumigatus in a modified solid state fermentation process

Abstract

Cellulases are used in many industries worldwide and there is an ever increasing need to isolate, produce or develop thermostable cellulases. Manipulation of fermentation techniques in order to obtain desirable product(s) can be one line of action. In this study Aspergillus fumigatus was grown on chopped wheat straw in a modified solid state fermentation (SSF) process carried out in the constant presence of isolated free water inside the fermentation chamber. The system was designed in order to make air inside the fermenter humid throughout the process, so that solid substrate does not dry out quickly. The crude endoglucanase produced by A. fumigatus under such conditions was found to be more thermostable than a number of previously reported endoglucanases. Various thermostability parameters were calculated for the crude endoglucanase. Half lives (T1/2) of the enzyme were 6930, 866 and 36 min at 60, 70 and 80°C, respectively. Enthalpies of activation of denaturation ( * D H ) were 254.04, 253.96 and 253.88 K J mole-1, at 60, 70 and 80°C respectively, whereas entropies of activation of denaturation ( * D S ) and free energy changes of activation of denaturation ( * D G ) were 406.45, 401.01, 406.07 J mole-1 K-1 and 118.69, 116.41, 110.53 kJ mole-1 at 60, 70 and 80°C, respectively. Keywords : Fermentation, cellulase, Aspergillus fumigatus, endoglucanase, thermostability