Influence of light qualities on antifungal lipopeptide synthesis in Bacillus amyloliquefaciens JBC36

Bacillus amyloliquefaciens JBC36 (JBC36) is a potent biocontrol agent and was proved to control green and blue molds of Satsuma mandarin (Citrus unshiu). Moreover, light qualities affected its biocontrol efficacy; green and red light significantly increased the antifungal activity of the antagonist in our previous study. The disparity in antagonism on Penicillium digitatum under different light qualities prompted us to investigate further to identify the factors responsible for the noted variation. Purification and quantification of antifungal lipopeptides by HPLC revealed that a three-fold higher quantity of fengycin and a two-fold higher quantity of iturin were produced in cultures incubated with red and green light sources in comparison with white light illumination. Gene expression analysis by real-time PCR also revealed nearly fourfold higher fenA transcripts in cultures subjected to green and red light in comparison with white light illumination. The lowest gene expression was observed with blue light illumination. This study clearly proved that light affects the synthesis of antifungal lipopeptides in JBC36. A light-based lipopeptide production strategy may lead to better exploitation of the microbes for overproduction of the antifungal secondary metabolites and crop disease management.