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

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 solidsubstrate 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, thermostabilit

Endoglucanase and total cellulase from newly isolated Rhizopus oryzae and Trichoderma reesei: production, characterization, and thermal stability

A multienzymatic complex production was evaluated, as well as endoglucanase and total cellulase characterization, during solid-state fermentation of rice industry wastes with Rhizopus oryzae CCT 7560 (newly isolated microorganism) and Trichoderma reesei QM 9414 (control). R. oryzae produced enzymes with higher activity at 15 h of fermentation (5.1 and 2.3 U g−1 to endoglucanase and total cellulase), while T. reesei produced them at 55 h (15.3 and 2.8 U g−1 to endoglucanase and total cellulase). The optimum temperature for total cellulase and endoglucanase was 60 °C. For Trichoderma and Rhizopus, the optimum pH was 5.0 and 6.0 for total cellulase and 6.0 and 5.0 for endoglucanase, respectively. The enzymes produced by Rhizopus presented higher stability at the temperature range evaluated (25–100 °C); the endoglucanase KM value was 20 times lower than the one found for Trichoderma. The characterization of the cellulolytic enzymes from the fungal species native of rice husk revealed that they can be more efficient than the genetically modified enzymes when rice husk and rice bran are used as substrates