CLONING OF A NEW ENDOGLUCANASE GENE FROM BACILLUS SP. BP-23 AND CHARACTERIZATION OF THE ENZYME - PERFORMANCE IN PAPER-MANUFACTURE FROM CEREAL STRAW

The gene celA, encoding an endoglucanase from the strain Bacillus sp. BP-23, was cloned and expressed in Escherichia coli. The nucleotide se quence of a 1867-bp DNA fragment containing the celA gene was determin ed, 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 celA gene product synthesized in E. co li showed activity on carboxymethylcellulose and lichenan but no activ ity was found on Avicel. Activity was enhanced in the presence of 10 m M Mg2+ and Ca2+ and showed its maximum at 40 degrees C and pH 4.0. Stu dy of the performance of CelA on paper manufacture from agricultural f ibres showed that treatment with the enzyme improved the properties of the pulp and the quality of paper. CelA treatment enhanced the physic al properties (stretch and tensile index) of paper from wheat straw, w hile dewatering properties were slightly diminished. Electron-microsco pe analysis showed that the surface of straw fibres was modified by Ce lA.