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 �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 �C. The app Tm increased from a control
value of 57 �C to a value of 66 �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.