Purification and characterization of acidic cellulase from Bacillus amyloliquefaciens SS35 for hydrolyzing Parthenium hysterophorus biomass

This study reports purification and characterization of an acidic endoglucanase (carboxymethylcellulase, CMCase) produced by Bacillus amyloliquefaciens SS35. Purification of enzyme was done using ion exchange chromatography (Yield=2.1%, Purification fold=18.5). The molecular weight of the CMCase was determined as approximate to 37 kDa. The purified CMCase was able to hydrolyze carboxymethylcellulose (CMC), barley--d-Glucan, lichenan, hydroxyethylcellulose, starch, and xylan, which indicated endoglucanase activity. However, the enzyme could not hydrolyze avicel and p-nitrophenyl--d-glucopyranoside (pNPG). These results were indications of absence of exoglucanase and -glucosidase activity in the enzyme. Optimum temperature and pH for CMCase activity were determined as 55 degrees C and 5.0, respectively. The enzyme also displayed high stability in temperature range of 20-40 degrees C and pH range of 5.0-9.0 for more than 20 h with significant residual CMCase activity of 80%. Five metal ions, viz. Co2+, Ca2+, K+, Na+, Mn2+ were found to be cofactors of the enzyme that enhanced its activity, while other metal ions such as Fe3+, Zn2+, Hg2+ rendered inhibition effect on the enzyme. Using Lineweaver-Burk plot, the kinetic parameters K-m and V-max for CMCase were determined as 0.33 mg/mL and 4.19 mol/mg/min, respectively. The asset of the enzyme was evaluated with hydrolysis of pretreated Parthenium hysterophorus. The total reducing sugar yield of 271 mg/g biomass was obtained. (c) 2014 American Institute of Chemical Engineers Environ Prog, 34: 810-818, 2015