Efficacy of Streptomyces philanthi RL-1-178 culture filtrate against growth and aflatoxin B1 production by two aflatoxigenic fungi on maize seeds

Abstract

The main objective of this study was to investigate the antifungal activities of a culture filtrate from Streptomyces philanthi RL-1-178 (culture filtrate RL-1-178) on growth and aflatoxin B1 production of Aspergillus parasiticus TISTR 3276 and A. flavus PSRDC-4 inoculated onto maize seeds. The culture filtrate RL-1-178 was first analyzed for its composition and found to contain 86 compounds with acetic acid (53.59%) as the major component. It could inhibit both the growth and the production of aflatoxin B1 (AFB1) of the two aflatoxigenic species. Complete prevention of AFB1 production was achieved with 5% (v/v) of the culture filtrate RL-1-178. It also inhibited spore germination depending on the duration of treatment. The culture filtrate RL-1-178 altered on the cell wall composition of the two aflatoxigenic fungal strains by causing loss of cytoplasm and distortion of the plasma membranes evident by transmission electron microscopy (TEM) image. For testing on maize seeds, the culture filtrate RL-1-178 at 30% (v/w of maize seeds) exhibited 100% and 98% inhibition on AFB1 production by A. parasiticus TISTR 3276 and A. flavus PSRDC-4, respectively, without affecting maize seed emergence. The culture filtrate RL-1-178 possessed antifungal activity against the two aflatoxigenic fungal strains grown on maize seeds. The effective dose was 30% (v/w) with no effect on the maize emergence (100%). Our results suggest that the culture filtrate from S. philanthi RL-1-178 can be used as a natural product that controls the two aflatoxigenic fungi.