Effect of cosolvents on the structural stability of endoglucanase from Aspergillus aculeatus.

The effects of cosolvents such as sucrose, glycerol, and sorbitol on endoglucanase have been studied by activity, circular dichroic spectroscopy, fluorescence, and apparent thermal transition temperature measurements. The endoglucanase activity increased by 4-fold at 40% cosolvent concentration under optimum conditions. The endoglucanase lost 50% of its activity when exposed to 90 degrees C for more than 30 min (1 h). In the presence of cosolvents, it maintained its original activity and native conformation as indicated by far UV-CD at 70 degrees C. The app T(m) increased from a control value of 57 degrees C to a value of 66 degrees C in the presence of 40% sucrose. The partial specific volume of endoglucanase was 0.723 mL/g in sodium acetate buffer. The preferential interaction parameters were negative in all cosolvents, and the maximum hydration of the protein was observed in 40% glycerol where the preferential interaction parameter was -0.126 g/g. The thermal stability of endoglucanase increased in the presence of cosolvents.