ISOLATION AND SELECTION OF Bacillus thuringiensis STRAINS PRODUCING CHITINASE FROM VEGETABLE SOIL IN BA BE COMMUNE, THAI NGUYEN PROVINCE

Abstract

With the aim of selecting Bacillus thuringiensis (Bt) strains exhibiting high chitinase activity and determining suitable culture conditions, this study focused on the isolation, selection, and identification of chitin-degrading Bt strains from vegetable-growing soils in Ba Bể commune, Thái Nguyên province, as well as on the determination of appropriate culture conditions for chitinase production. The results showed that six bacterial strains capable of chitin degradation were isolated, with clearance zone diameters ranging from 0.54 to 2.35 cm. Among them, strain BT-16 exhibited the highest chitinase activity, reaching 1.52 U/mL. Based on 16S rRNA gene sequence analysis, strain BT-16 was identified as Bacillus thuringiensis gv. thuringiensis and designated Bacillus thuringiensis gv. thuringiensis BT-16. Under optimal conditions - cultivation for 3 days in LB medium supplemented with 1.5% chitin and 0.5% galactose at 35°C and pH 7.0 - strain BT-16 achieved the highest chitinase activity of 17.51 U/mL. These findings suggest that strain BT-16 has strong potential for application in the production of biological pesticides, contributing to safe and sustainable agricultural production.