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Identification of a Broad-Spectrum Antifungal Chitinase from Bacillus Subtilis Strain BC121

Abstract

A chitinase enzyme, Chi25, was purified from the supernatant of cultured Bacillus subtilis strain BC121 by ammonium sulfate precipitation and chitin affinity chromatography. The purity of the enzyme was confirmed by SDS-PAGE and RP-HPLC analysis and the molecular weight of the enzyme was estimated to be approx. 25 kDa. The enzyme was stable over a pH range of 6–7.5, while the optimal pH for enzyme activity was 6.5. Chi25 was stable over a temperature range of 25–40 °C with 35 °C as the optimal temperature for activity. Bioassay of Chi25 demonstrated the inhibition of spore germination and hyphal extension of important plant pathogenic fungi. Results of the glasshouse trials revealed that the wild-type strain (BC121) reduced fusarium wilt incidence by 80%. Comparative analysis of both the wild-type strain (BC121) and the mutant strain of this bacterium (BC121M) revealed that the antagonism of the BC121 strain against plant pathogenic fungi both in vitro and in vivo is due to the Chi25 enzyme.

Saleem Basha and Kandasamy Ulaganathan

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