The role of trace metal ions in aflatoxin B1 degradation by Flavobacterium aurantiacum.
Flavobacterium aurantiacum NRRL B-184 possesses the ability to degrade aflatoxin B1 in solution and in several food items. Aflatoxin B1 is a potent carcinogen that causes significant economic losses to the agricultural and food industry. The role of trace metal ions (Cu2+, Mn2+, Zn2+, and Co2+) were studied in an effort to understand the enzymatic system involved in aflatoxin B1 degradation by F aurantiacum. The effect of divalent chelators (EDTA and 1,10-phenanthroline [OPT]) in the presence of the trace metal ions was studied as well. Aflatoxin B1 (10 microg/ml) was added to 72-h cultures of F aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). HPLC was used to determine aflatoxin B1 concentration in these cultures. Incubating cells at 30 degrees C with 1 and 10 mM Cu2+, Mn2+, and Zn2+ significantly decreased aflatoxin B degradation after 4 and 24 h (P < 0.05). Decreased degradation was also observed with 1 and 10 mM Cu2+ and Zn2+ after 48 h and with 0.1 mM Cu2+ after 24 and 48 h. Co2+ did not have a significant effect on aflatoxin B1 degradation. EDTA and OPT did not counter the inhibition in the presence of Cu2+. The addition of 1 mM EDTA countered the inhibition by 1 mM Mn2+ after 4 and 24 h, but 1 mM OPT did not counter the inhibition by 10 mM Mn2+ after 4 and 24 h. OPT countered the inhibition by 1 mM Zn2+ after 4 and 48 h. These trace elements inhibit aflatoxin B1 degradation by F aurantiacum. In addition, their presence necessitates higher concentrations (>1 mM) of EDTA and OPT for the removal of their inhibitory effect.
D'Souza
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Center for Food Safety and Quality Enhancement, Department of Food Science and Technology, The University of Georgia, Griffin 30223-1797, USA.
Brackett
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D016604:Aflatoxin B1 / Q000378:metabolism*; D001673:Biodegradation, Environmental / Q000187:drug effects; D002413:Cations, Divalent / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D004492:Edetic Acid / Q000494:pharmacology; D005417:Flavobacterium / Q000254:growth & development / Q000378:metabolism*; D014131:Trace Elements / Q000494:pharmacology*
D002413:Cations, Divalent; D014131:Trace Elements; D004492:Edetic Acid; D016604:Aflatoxin B1