Kinetics of aflatoxin biosynthesis by Aspergillus parasiticus in the presence of N(alpha)-palmitoyl-L-lysyl-L-lysine-ethyl ester dihydrochloride or dichlorvos.
N(alpha)-Palmitoyl-L-lysyl-L-lysine-ethyl ester dihydrochloride (PLL) has antimicrobial properties and may be useful as a food preservative. This study was conducted to see if PLL can inhibit growth and synthesis of aflatoxin by Aspergillus parasiticus. Growth of mold and accumulation of aflatoxins were monitored for up to 15 days. To compare these data with those of a known inhibitor of aflatoxin synthesis, dichlorvos was added to media, and mold growth and aflatoxin accumulation were monitored. The kinetic model of Brown and Vass that correlates growth and formation of secondary metabolites was applied to results of this study, and values for maturation time (t(m)) and aflatoxin accumulation rate constant (alpha) were calculated. Values of t(m) decreased when cultures contained PLL, whereas presence of dichlorvos resulted in a considerable increase. The lag phase of mold growth increased in the presence of PLL. The values of alpha increased with an increasing amount (up to 300 ppm) of PLL in media. Higher concentrations of PLL decreased the value of alpha. All levels of dichlorvos tested decreased the value of alpha. The aflatoxin accumulation rate constant (alpha) as a function of concentration of additive (C) followed the general equation: \documentclass{article}\pagestyle{empty}\begin{document}$$\alpha = \frac{{\alpha _m C\exp (- {C \mathord{\left/ {\vphantom {C {K_i }}} \right. \kern-\nulldelimiterspace} {K_i }})}}{{C + K_a }}$$\end{document} where alpha(m), K(a), and K(i) are constants.
Department of Food Science and the Food Research Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706.
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Yousef
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Marth