2011 Annual Report
1a.Objectives (from AD-416)
To collaborate in the development of a real-time electronic sensor to detect the growth of Aspergillus flavus on corn.
1b.Approach (from AD-416)
ARS will perform microbiological experiments to obtain data on the volatile gases produced by Aspergillus flavus growing on corn in vitro under laboratory conditions. Sensor Development Corporation will utilize this data to develop a chip-based electronic sensor that detects the major volatiles as determined by ARS.
Aflatoxin (a potent carcinogen), produced by some isolates of Aspergillus (A.) flavus, is the most potent, natural hepatocarcinogen known and is banned by the Food & Drug Adminstration at, and above, 20 parts per million. This research identifies unique secondary metabolic volatiles produced by aflatoxin-producing isolates of A. flavus that separate them from the non-aflatoxin producing isolates. Our cooperator, Sensor Development Corporation, has used this data to develop and manufacture electronic sensors to detect these volatiles and potentially warn corn-processing personnel of the growth of aflatoxigenic A. flavus. Experiments performed in our lab during previous years identified volatiles unique for aflatoxigenic A. flavus isolates when grown on sterile, cracked corn. During the first half of FY 2011 we studied such volatiles when the toxigenic and non-toxigenic isolates were grown separately on a defined liquid medium. Beginning in February, 2011, we began the determination of A. flavus volatile production when grown on wet (20% moisture) non-sterile corn. This presented a new set of growth variables: (1) the non-sterile corn nutrients would differ from those presented by sterilized corn due to the steam/heat sterilizing process, and (2) competition for these nutrients by naturally occurring microorganisms on the corn. To date, we have studied the volatiles produced by two non-toxigenic and three toxigenic strains of this fungus. Each strain has been studied at least twice in separate experiments. The experiments are ten days in duration with samples examined on days 1-5, 8, and 10. The vast majority of volatiles are produced during the first five days after growth begins. Very few volatiles are detected after the first five days of growth. The amount of data obtained is huge and we are currently processing the volatile and aflatoxin data from both the liquid medium and non-sterile, cracked corn as nutrients experiments. Scientists from Sensor Development Corporation are expected to visit us sometime during the summer of 2011. Research progress was monitored through teleconferencing, frequent email communications and reports.