Production, purification, and characterization of a thermo-alkali stable and metal-tolerant carboxymethylcellulase from newly isolated Bacillus methylotrophicus Y37

Abstract

A carboxymethylcellulose (CMC)-degrading bacterium was isolated from soil, identified as Bacillus methylotrophicus according to the physiological properties and analyses of 16S rRNA and a partial sequence of the gyrase A (gyrA) gene, and named as B. methylotrophicus Y37. The CMCase enzyme was purified to homogeneity by 20.4-fold with 21.73% recovery using single-step hydrophobic interaction chromatography and biochemically characterized. CMCase showed a molecular weight of approximately 50 kDa as determined by SDS-PAGE. The activity profile of the CMCase enzyme exhibited optimum activity at 45°C and pH 5.0. The activity was highly stable at alkaline pH levels. More than 90% of the original CMCase activity was maintained at relatively high temperatures ranging from 55 to 65°C. The enzyme activity was induced by Ca2+, Cd2+, Co2+, K+, Mg2+, and Na1+, whereas it was strongly inhibited by phenylmethanesulfonyl fluoride and iodoacetic acid. The enzyme tolerated Hg2+ up to 10 mM and presented hydrolytic activity towards glucan, filter paper, laminarin, and CMC but not o-nitrophenyl β-D-galactopyranoside. Kinetic analysis of the purified enzyme showed Km and Vmax values of 0.19 mg mL-1 and 7.46 U mL-1, respectively. The biochemical properties of this CMCase make the enzyme a good candidate for many industrial applications.