Endochitinases, hydrolyzing chitin randomly at internal sites, can be used not only for production of useful chitin derivates, but also as control agent against phytopathogenic fungi or for enhancing of insecticidal activity of Bacillus thuringiensis (Bt). A total of 158 B. thuringiensis isolates were recovered from soil and leaves samples collected in Hanoi. Of these, 64 isolates produced bipyramidal and cuboidal inclusions. Serologically tested the 64 isolates showed that 46 were identified to Bacillus thuringiensis serovar kurstaki (Btk). Of 36 strains Btk showed chitin hydrolysis activity, 35 strains contained chiA gene. A strain designated MSS1.l, exhibited the strongest chitin hydrolysis activity. A 2.0-kb DNA fragment, obtained by PCR from the strain MSS 1.1 using the chiA specific primers, was cloned into the pGEM- Teasy cloning vector. The chiA sequence of 203IBp showed almost identity (99 percent) to that of the referent strain B. thuringiensis serovar kurstaki HD73 (GenBank: EF581163). Although of 10 nucleotides substitution, but only 5 amino acid changes were identified and generated one sequence of BamHI (GGATCC) at nucleotide position 915. The strain B. thuringiensis serovar kurstaki MSS 1.1 containing the chiA gene with high chitin hydrolyzing activity as characterized in this study is a promising strain for endochitinase - synergist of B. thuringiensis biopesticide and suggested as an important genetic material for medicine and pharmaceutical uses.
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