A novel thermostable cellulase from Fervidobacterium nodosum

A novel cellulase gene encoding a thermostable endoglucanase from the thermophilic eubacterium Fervidobacterium nodosum Rt17-B1 was cloned and expressed, which is the first cellulase cloned from the organisms of genus Fervidobacterium and designated as FnCel5A for being a member of glycoside hydrolase family 5, and the enzymatic properties were characterized. The cellulase was overexpressed in Escherichia coli with a high protein content and good solubility in water, and could be easily purified. The purified recombinant cellulase shows high hydrolytic activities on carboxylmethyl cellulose, regenerated amorphous cellulose, β-d-glucan from barley and galactomannan, with the optimum temperature of 80–83 °C and the optimum pH of 5.0–5.5. Furthermore, this enzyme is highly thermostable and has a half-life of 48 h at 80 °C. With such a combination of thermostability and high activities, this cellulase is expected to be useful for hydrolysis of cellulosic and hemicellulosic substrates at high temperatures, and for industrial hydrolysis of plant cellulose during long-time processing at the elevated temperatures, particularly in converting biomass into biofuels.