Aims: The aim of this study was to improve the antagonistic activity of Bacillus subtilis JA towards Fusarium graminearum by screening high-yielding mutant using the atmospheric-pressure plasma jet (APPJ).
Methods and results: Atmospheric-pressure plasma jet was applied as mutagenic source for breeding high-yielding mutant strain. Helium was used as APPJ operating gas. The mutation effects of different treatment times of APPJ were studied. The mutant strain designated as B. subtilis B06 was successfully screened out, which showed higher antagonistic activity against F. graminearum in vitro. Its inhibition zone against the indicator fungus increased by 23% compared to the original one. HPLC and ESI (electrospray ionization) mass spectrometry analysis indicated that antifungal compounds produced by the mutant and original strain belonged to the lipopeptide, surfactin and iturin families. The mutant strain showed favourable properties of faster growth in the fermentation process and higher production of antibiotics. The lipopeptide production of the mutant was 2.3-fold as that of the original strain.
Conclusions: A mutant strain with strong antagonistic activity and high yielding of antibiotics was obtained by APPJ in this study. The mutant could be used as a promising biocontrol agent in agriculture.
Significance and impact of study: This study provides a novel mutagenic source for breeding high-yielding microbial mutant, which would be very useful in the application of some valuable metabolites from micro-organism.