INHIBITION OF GROWTH AND AFLATOXIN PRODUCTION OF ASPERGILLUS-FLAVUS BY LACTOBACILLUS SPECIES

A mixture of Lactobacillus species from a commercial silage inoculum r educed mold growth and inhibited anatoxin production by Aspergillus fl avus subsp. parasiticus. Actively growing Lactobacillus spp. cells tot ally inhibited germination of mold spores. Culture supernatant broth f rom the mixture of strains inhibited mold growth but did not destroy m old spore viability. Some mold spores were observed microscopically to have germinated and produced short nonbranching germ tubes; then grow th ceased. While the pH of the culture broth and supernatant were abou t 4.0, acidification of nonfermented broth to pH 4.0 with HCl and lact ic acid did not cause a similar inhibition of spore germination. The m ixture of Lactobacillus species growing ina dialysis sack inhibited an atoxin production by the A. flavus culture growing outside of the sack in broth, whereas mold growth was not affected. The pH values outside of the dialysis sack in the control and the treatments were similar ( 6 to 7) throughout the incubation period. When a dialysis sack with a molecular weight cutoff (MWCO) of 1,000 was used, there was little inh ibition of aflatoxin B-1 production, bur with MWCOs of 6,000 to 8,000 and 12,000 to 14.000 aflatoxin production was greatly inhibited. In mi xed culture experiments, levels of aflatoxin B-1 and G(1) were depress ed compared to the control (monoculture). Mold growth in this case was also reduced compared to the monoculture system. Purified isolates of Lactobacillus from the commercial mixture had a slight effect on mold growth and aflatoxin production, but supernatant liquid of one isolat e was quite inhibitory to production of aflatoxins B-1 and G(1), witho ut affecting mold growth.