Cloning and expression of low temperature active endoglucanase EG5C from Paenibacillus sp. IHB B 3084

The endoglucanase gene designated as EG5C encoding cold active endoglucanase produced by Paenibacillus sp. IHB B 3084 was cloned and expressed in Escherichia coli BL21(DE3). The gene consisting of 1719 bp open reading frame encoded a protein of 573 amino acids with a predicted molecular weight of 63.5 kDa. The presence of N-terminal catalytic domain of the glycosyl hydrolase family 5 (GH5) and C-terminal carbohydrate binding X2 domain suggested the modular nature of the enzyme. The native signal peptide of EG5C was capable of efficiently secreting the enzyme with near equal activities in the cytoplasmic and extracellular fractions. The recombinant enzyme purified 9.46 fold to homogeneity with 22.33% yield gave 7.758 IU/mg specific activity. The enzyme was stable over the broad pH range of 4-12 with more than 50% residual activity. The optimal activity was at 40 °C with 70% relative activity at 5 °C. The low temperature activity despite the shorter linker region suggested a novel cold adaptation mechanism by the enzyme. The enzyme displayed higher activity on carboxymethylcellulose than avicel which is useful in maintaining the tensile strength of fiber. The efficient secretion and low temperature activity offer prospect for large-scale production and industrial application of the endoglucanase.