Characterization of carboxymethyl cellulase produced by Trichoderma asperellum

Background:  The present study characterized extracellular carboxymethyl cellulase (CMCase), an enzyme catalyzes the hydrolysis of the cellulose, from  Trichoderma asperellum  PQ34 that was isolated from agricultural cultivation soil in Thua Thien Hue, Vietnam. Methods:  CMCase was produced by culturing  T. asperellum  PQ34 on Czapek-Dox medium supplemented with carboxymethyl cellulose (CMC) at 28oC for 96 h at a shaking speed of 150 rpm. Enzyme activity was spectrophotometerically determined with CMC used as a substrate and the absorbance was measured at 540 nm. The molecular weight of CMCase was determined by zymogram based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with 0.2% CMC. Results:  CMCase achieved the highest activity after 4 days of culture with the optimal pH and temperature at 4 and 55°C. The enzyme maintains pH and thermal stability in the range of 4-5 and 10-40°C and the relative activity of both is more than 90%. The presence of metal ions at 5 mM such as Ca 2+ , Al 3+ , or Co 2+  increased the enzyme activity up to 133%, 124%, and 217%, respectively. CMCase was stable with 1 mM ethylenediaminetetraacetic acid and 1 M urea, but inhibited by 5% sodium dodecyl sulfate (SDS) and 5% Triton-X100. Zymographic analysis showed that CMCase from  T. asperellum  PQ34 consists of two enzymes with a molecular weight of about 31 and 66 kDa. Conclusion:  CMCases from  T. asperellum  PQ34 exhibited characteristics of an acidic and thermostable enzyme. The interaction of Co 2+  and CMCase resulted in a significant increase in enzyme activity, however they were strongly inhibited by 5% SDS. Keywords: Carboxymethyl cellulase; Cellulase; Endo-β-1,4-glucanase,  Trichoderma asperellum