Construction and screening of metagenomic library derived from soil for β-1, 4-endoglucanase gene

A metagenomic library consisting of 7500 clones was constructed from the soil continuously irrigated with effluents of paper and pulp mill. A cellulase positive clone H-10 was identified by function based screening. A β-1, 4- endoglucanase gene with an open reading frame of 1499 bp was identified from this positive clone. The deduced amino acid sequence analysis revealed that amplified β-1, 4-endoglucanase belongs to GH5 and shares 98% similarity with Bacillus subtilis (EF070194), 95% with Bacillus subtilis IARI-SP-1(KF240847) 96% with B. subtilis (AY183475) and 95% with uncultured bacterium clone (JX567739). Clone H-10 indicated higher CMCase activity of 1 IU/ml on the substrate CMC as compared to rice straw (0.5 IU/ml). The characterization of enzymes revealed its pH optima between 8.5–9 and retained 80% of activity at pH 11. The thermal profile of the enzyme indicated broad range of thermotolerance.