Variation in fungal microbiome (mycobiome) and aflatoxins during simulated storage of in-shell peanuts and peanut kernels

Abstract

Internal transcribed spacer 2 (ITS2) sequencing was used to characterize the peanut mycobiome during 90 days storage at five conditions. The fungal diversity in in-shell peanuts was higher with 110 operational taxonomic units (OTUs) and 41 genera than peanut kernels (91 OTUs and 37 genera). This means that the micro-environment in shell is more suitable for maintaining fungal diversity. At 20–30 d, Rhizopus, Eurotium and Wallemia were predominant in in-shell peanuts. In peanut kernels, Rhizopus (>30%) and Eurotium (>20%) were predominant at 10–20 d and 30 d, respectively. The relative abundances of Rhizopus, Eurotium and Wallemia were higher than Aspergillus, because they were xerophilic and grew well on substrates with low water activity (aw). During growth, they released metabolic water, thereby favoring the growth of Aspergillus. Therefore, from 30 to 90 d, the relative abundance of Aspergillus increased while that of Rhizopus, Eurotium and Wallemia decreased. Principal Coordinate Analysis (PCoA) revealed that peanuts stored for 60–90 days and for 10–30 days clustered differently from each other. Due to low aw values (0.34–0.72) and low levels of A. flavus, nine of 51 samples were contaminated with aflatoxins.

The peanut pods-associated microbiota and their effects on aflatoxin contamination

“…Except for the potential antagonists, we found that more inthe-shell fungi (more than 86% of 45) were significantly positively correlated with A. flavus, which may play a beneficial role in the growth of A. flavus. Our previous experiments demonstrated the antagonism of Trichoderma and Bacillus with A. flavus[25][26][27], consistent with our correlation analysis. To further search for fungi and bacteria associated with these known antagonists, we also performed a correlation analysis between antagonists and other microorganisms associated with peanuts.…”

Antioxidant‐related catalase CTA1 regulates development, aflatoxin biosynthesis, and virulence in pathogenic fungus Aspergillus flavus

“…Aflatoxin B1 (AFB1) of all the mycotoxin holds the highest toxicity. It is widely distributed across agricultural products and acts as a potent carcinogen, mutagen and teratogen (Yang et al, 2015;Han et al, 2016;Xing et al, 2016). The protracted consumption of AFs in both humans and animals leads to immunosuppression, growth impairment and DNA damage (Khlangwiset et al, 2011;Zhang et al, 2015).…”

Transcriptome Sequencing Revealed an Inhibitory Mechanism of Aspergillus flavus Asexual Development and Aflatoxin Metabolism by Soy-Fermenting Non-Aflatoxigenic Aspergillus

“…This fungus is also an opportunistic pathogen for immunocompromised patients, which is the second most common cause of aspergillosis after A. fumigatus [ 3 ]. A. flavus is notorious for its production of one of the most carcinogenic mycotoxins, aflatoxin [ 4 ], which has an extensive relationship with liver cancer [ 5 ]. Therefore, it is important to develop effective and safe approaches to control this fungus and inhibit the production of aflatoxins for food safety and human health.…”