Control of Aspergillus flavus Link ex Fries and A. parasiticus Speare growth using bacterial chitinases
1996
Doyungan, S.M.M.
Bacillus circulans B1037 (5Bc), Arthrobacter luteus B1077 (6Al), B. circulans B1045 (7Bc), Streptomyces griseus BB1562 (9 Sg), and Serratia marcescens LPC19 B1748 (11 Sm) and S. marcescens LPM42 B1749 (14 Sm) when grown in chitin broth, excreted chitinase enzymes into the culture medium. The crude enzyme extract showed mycolytic activity as shown by the release of N-acetylglucosamine (GlcNAc) when live mycelia of A. flavus and A. parasiticus were used as substrates. The undiluted crude enzyme extracts and most of the 4:1 diluted-extracts were effective in reducing germination of fungal spores of Aspergillus flavus and A. parasiticus and in restricting mycelial growth. No evidence of hyphal tip dwelling was observed contrary to reports in many literatures. Growing the treated mycelial balls of A. flavus and A. parasiticus on PDA showed significant reduction in the diameter of colonies compared to the negative control 24 hours after plating but not 48 hours after plating. However, the crude chitinase extracts can control the growth of the two aflatoxigenic species of Aspergillus in corn kernels as indicated by the significant reduction in the number of infected kernels. Analysis of the cytotoxic potential of the crude enzyme extracts revealed that all extracts were toxic to the mouse fibroblasts at various dilutions. However, extract-treated corn kernels were non-toxic to the fibroblasts except those treated with A. luteus and S. griseus extracts
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