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

Authors: PAUL CHIJIOKE OZIOKO, SABINUS OSCAR ONYEBUCHI EZE, FERDINAND CHIEMEKA CHILAKA

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, \beta-glucosidase, and total cellulase activities, respectively. Temperature optima of 50 °C were recorded for \beta-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 V_{max} and K_m of 2427.18 \mumol/min and 15.12 mg cellulose and endoglucanase has values of 955.11 \mumol/min and 2.39 mg Na-CMC, while the values of \beta-glucosidase are 946.97 \mumol/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.

Keywords: Achatina achatina, cellulases, purifications, characterization, sodium carboxymethyl cellulose (Na-CMC), cellobiose

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