Primary Study on Isolation of Cellulase from a Thermobifida and Its Enzymatic Properties

Nucleotide sequences of the 16S rRNA gene of Thermobifida (formerly Thermomonospora) Q-0 was analyzed by MEGA v.3, and the phylogenetic tree showed the relationship between different strains in Thermobifida genus. A carboxymethyl cellulase I (CMCase I) was purified by fractional ammonium sulphate precipitation and ion exchange chromatography on DEAE-Sephadex. The enzyme showed the highest activity at 60degC and pH 8.0. It exhibited high thermostability and wide pH stability (6.0 - 9.0). The enzyme retained 100% activity at 50degC for 120 min. The half-lives of the CMCase at 70degC and 80degC were about 75 min and 110 min, respectively. The effects of some metal ions and inhibitors on the activities of the CMCases were examined. Metal ions such as K⁺, Na⁺, Cu²⁺, Fe³⁺ did not influence the enzyme activity. Mg²⁺ ions caused increase, while Hg²⁺, Mn²⁺, Ag²⁺, Zn²⁺, caused a decrease in the activity. Ca²⁺ was slightly inhibitory to CMCase. The enzyme activity was complete inhibited by EDTA, which indicated the enzyme activity required certain metal ions for activation and stabilization.