Partial purification and characterization of cellulases from digestive tracts of the African giant snail (Achatina achatina)

Abstract

Crude cellulase was extracted from the digestive tracts of 30 mature Achatina achatina and subjected to a 3-step purification process of ammonium sulfate precipitation, dialysis, and gel filtration. This purification procedure gave 3 prominent enzyme activity peaks that coincided with protein peaks and were designated A, B, and C, corresponding to high endoglucanase, β-glucosidase, and total cellulase activities, respectively. Temperature optima of 50 °C were recorded for β-glucosidase and total cellulase while 45 °C was recorded for endoglucanase. Total cellulase, glucosidase, and endoglucanase showed maximum activities at pH values of 5.5, 4.5, and 7.5, respectively. Kinetic studies show that total cellulase has a Vmax and Km of 2427.18 μmol/min and 15.12 mg cellulose and endoglucanase has values of 955.11 μmol/min and 2.39 mg Na-CMC, while the values of β-glucosidase are 946.97 μmol/min and 4.3 mM cellobiose, respectively. This study shows that cellulases from digestive tracts of A. achatina could be utilized for degradation of cellulose-containing materials because of their high thermostability and acid/alkali stability, which reflect the potential commercial significance of the enzyme.