Cloning of a new endoglucanase gene from Bacillus sp. BP-23 and characterisation of the enzyme. Performance in paper manufacture from cereal straw

Abstract

The gene ce1A, encoding an endoglucanase from the strain Bacillus sp. BP-23, was cloned and expressed in Escherichia coli. The nucleotide sequence of a 1867-bp DNA fragment containing the ce1A gene was determined, revealing an open reading frame of 1200 nucleotides that encodes a protein of 44,803 Da. The deduced amino acid sequence of the encoded enzyme shows high homology to those of enzymes belonging to subtype 4 of the family-A cellulases. The ce1A gene product synthesized in E. coli showed activity on carboxymethylcellulose and lichenan but no activity was found on Avicel. Activity was enhanced in the presence of 10 mM Mg2+ and Ca2+ and showed its maximum at 40 degrees C and pH 4.0. Study of the performance of Ce1A on paper manufacture from agricultural fibres showed that treatment with the enzyme improved the properties of the pulp and the quality of paper. Ce1A treatment enhanced the physical properties (stretch and tensile index) of paper from wheat straw, while dewatering properties were slightly diminished. Electron-microscope analysis showed that the surface of straw fibres was modified by Ce1A.