Primary study on isolation of cellulase from a Thermobifida and its enzymatic properties

摘要

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 60°C and pH 8.0.It exhibited high thermostability and wide pH stability (6.0 -9.0). The enzyme retained 100% activity at 50°C for 120min. The half-lives of the CMCase at 70°C and 80°C were about 75min and 110min, 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.