Variation with in vitro analysis of volatile profiles among Aspergillus flavus strains from Louisiana

Authors: Moore, Geromy; Lloyd, Steven

Submitted to: Separations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fungi produce many metabolites as gases or, in other words, volatile organic compounds (VOCs). In light of recent studies showing that VOCs produced by non-aflatoxigenic A. flavus strains have the potential to inhibit growth and toxin production, this lab wanted to determine if a non-aflatoxigenic strain, native to Louisiana with proven inhibitory properties against toxin producing strains, produced its own unique VOCs that might serve as potential biocontrol compounds. Similarly, we analyzed the VOC profiles of three toxin producing Aspergillus strains from Louisiana to see if they produced VOCs that could be used as biomarkers to identify the presence of toxin producing strains in a field of storage environment. This study resulted in 13 potential biocontrol compounds from the non-aflatoxigenic strain examined, as well as six compounds that have potential as biomarkers to detect the presence of toxin producing strains.

Technical Abstract: Using four Aspergillus strains (one non-aflatoxigenic and three aflatoxigenic) from the same geographic region (Louisiana), we devised experiments whereby each aflatoxigenic strain was grown on four different types of synthetic media and cracked kernels from two different genotypes of corn: one susceptible (VA35) and one resistant (MI82) to A. flavus infection. The headspaces of these fungi on each substrate were captured and and analyzed using GC-MS. For synthetic media, the cultures were incubated for one week before headspace collection, while the corn samples were subjected to three capture time points: 48 h, one week and two weeks. Ten VOCs were found with multiple replicates for each strain, multiple strains and multiple synthetic media types. Many more VOCs were found with only one replicate and grouped as singletons in each strain's headspace profile. Fewer VOCs (five) were found with multiple replicates, strains and corn types when profiles from corn kernels were assessed. However, the numbers of singleton VOCs far exceeded those found with synthetic media. Some VOCs were very common and contributed large percentages to headspace profiles. We found that VOC production is very much substrate-dependent. We also found that each strain produced at least one unique VOC that was not captured with any of the other strains examined. We have a pool of VOCs that were unique to our non-aflatoxigenic strain to test for potential biocontrol properties, as well as some that are found only with our aflatoxigenic strains to further examine as biomarkers for detecting the presence of aflatoxin producing strains.