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Time course study of substrate utilization by Aspergillus flavus in medium simulating corn (Zea mays) kernels
Jay E Mellon1, Michael K Dowd, Peter J Cotty
1Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 19687, New Orleans, Louisiana 70179, USA. jmellon@srrc.ars.usda.gov
Journal of Agricultural and Food Chemistry
|January 24, 2002
Summary
Aspergillus flavus utilizes corn starch and triglycerides simultaneously, producing aflatoxin B(1) and metabolites like mannitol. This fungus shows less substrate discrimination than previously thought.
Area of Science:
- Microbiology
- Mycology
- Biochemistry
Background:
- Aspergillus flavus is a significant agricultural pathogen.
- Understanding its nutrient utilization is crucial for controlling its growth and mycotoxin production.
- Corn kernels contain starch, triglycerides, and zein as primary nutrient reserves.
Purpose of the Study:
- To investigate the in vitro utilization of major corn reserve materials by Aspergillus flavus.
- To correlate nutrient consumption with fungal growth, aflatoxin B(1) production, and metabolite formation.
- To assess substrate discrimination by A. flavus.
Main Methods:
- In vitro fermentation of A. flavus over 7 days.
- Monitoring of starch, triglyceride, and zein hydrolysis.
- Quantification of glucose, free fatty acids, aflatoxin B(1), and fungal biomass.
- Detection and quantification of fungal metabolites (arabitol, erythritol, mannitol, trehalose, kojic acid).
Main Results:
- Simultaneous hydrolysis of starch and triglycerides occurred, peaking on day 2.
- Aflatoxin B(1) production increased after 36 hours, peaking on day 4, paralleling fungal biomass.
- Mannitol was the most abundant metabolite, with production timing mirroring aflatoxin B(1).
- A. flavus showed less substrate discrimination compared to its known preference for simple carbohydrates.
Conclusions:
- A. flavus can efficiently utilize complex substrates like starch and triglycerides.
- Nutrient availability and metabolism are closely linked to aflatoxin B(1) biosynthesis.
- The findings challenge previous assumptions about A. flavus substrate selectivity.