Molecular characterization of chitinase producing Bacillus thuringiensis

Abstract

Aim: In the present study, twenty eight Bacillus thuringiensis (Bt) strains were studied for their potential to hydrolyze chitin. Methodology: The chitinolytic potential of Bt strains were determined using modified chitinase screening media (CSM) containing colloidal chitin as substrate. The potential Bt strains were screened for the presence of cry genes using PCR and further molecular characterized using 16S rDNA amplification and sequencing. Results: Among 28 Bt strains, 10 strains showed positive results by producing clear halo zone around bacterial colonies and the maximum chitinase solubilization index was observed in Bt-13 whereas the minimum solubilization index was observed in Bt-27 strain. Further, the chitinase assay revealed the minimum enzyme activity in Bt-26 (3.78 ± 0.101 U ml-1) whereas the maximum activity was observed in strain Bt-2 (10.19 ± 0.651 U ml-1). PCR based chitinase gene screening also revealed the presence of both endochitinase and exochitinase genes in these Bt strains. The potent Bt strains viz., Bt-7, Bt-10, Bt-11, Bt-13 and Bt-27 on the basis of chitinase production were molecular characterized based on 16S rDNA and sequencing results reveled their greatest sequence identity Bacillus thuringiensis. Interpretation: Results showed that the high chitinase activity of these Bt strains may be due to the presence of chitinase genes, which need to be explored for further biological applications.