Purification and characterization of an antifungal protein from Bacillus subtilis XL62 isolated in Vietnam.

Bacillus subtilis is considered as a potential antagonist for fungal control due to its ability to produce a wide range of antibiotics. This study determines the antifungal activity of the native B. subtilis XL62 and we purify, identify, and characterize the antifungal protein. The results show that the growth inhibitory activity to Fusarium oxysporum and Rhizoctonia solani of the crude supernatant of B. subtilis XL62 was proportional to the concentration. At the highest concentration (50%), the growth inhibition reached 90% and 100% for F. oxysporum, and R. solani, respectively. Furthermore, the crude supernatant of B. subtilis XL62 also inhibited the germination and growth of R. solani. The growth of sclerotia was almost completely inhibited at the concentration of 20% and the ability to germinate was lost at the concentration of 50%. Antifungal proteins were isolated from the crude bacterial supernatant using ammonium sulphate precipitation followed by passage over DEAE-cellulose and Biogel P100 columns. The purified protein had an apparent molecular mass of 22 kDa. Its antifungal activity was retained even at 100 °C, for 60 min and after treatment with proteinase K (0.5-2.5 μg/ml). The results of protein identification using a MALDI-TOF/TOF mass spectrometer suggest that the purified protein is indeed a chitin-binding protein. [ABSTRACT FROM AUTHOR]