X-ray Irradiation of Aspergillus flavus and Aflatoxin B1 Contaminated Maize

Authors: GLESENER, HANNAH - Arizona State University; ABDOLLAZEDEH, DARYA - Arizona State University; MUSE, CHRISTOPHER - Arizona State University; KRAJMALNIK-BROWN, ROAS - Arizona State University; Weaver, Mark; VOTH-GAEDDERT, LEE - Arizona State University

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2024
Publication Date: 7/25/2024
Citation: Glesener, H., Abdollazedeh, D., Muse, C., Krajmalnik-Brown, R., Weaver, M.A., Voth-Gaeddert, L. 2024. X-ray Irradiation of Aspergillus flavus and Aflatoxin B1 Contaminated Maize . Toxins. https://doi.org/10.3390/toxins16080329.
DOI: https://doi.org/10.3390/toxins16080329

Interpretive Summary: Many agricultural commodities and food products can be contaminated with aflatoxin, a metabolite of the pathogen Aspergillus flavus, and this problem is particularly common in maize grown in low-yield, high-stress environments. We conducted experiments to see if the pathogen could be killed in research materials while preserving the physical qualities of the research materials. White maize was artificially inoculated with A. flavus, becoming contaminated with aflatoxin. This material was then subjected to a range of exposures to X-ray irradiation to determine the radiation dose-response for A. flavus and for the aflatoxin. No viable A. flavus was recovered after exposure = 2.5kGy, but there was no significant effect on the aflatoxin concentration at any dose up to 3kGy.

Technical Abstract: Food crops around the world are commonly contaminated with Aspergillus flavus, which can produce the carcinogenic mycotoxin Aflatoxin B1 (AFB1). The objective of this study is to establish a sterilization method for studying AFB1 in naturally contaminated food products in the laboratory. We aimed to achieve this objective by establishing a sufficient dose of X-ray irradiation–a non-radioactive, non-thermal, and non-chemical method of food sterilization–to destroy viability of A. flavus while maintaining AFB1 concentration in maize. A batch of ground maize was inoculated with an aflatoxigenic A. flavus strain to roughly 300 ppb. The maize was irradiated with a range of  X-ray irradiation doses: 0.0, 1.0, 1.5, 2.0, 2.5, and 3.0 kGy. A. flavus was quantified by dilution plating on potato dextrose agar and modified rose bengal media for viability and qPCR for gene presence. AFB1 was quantified in maize by HPLC and ELISA. A. flavus viability, but not gene copies, changed significantly with increasing doses of radiation. Dilution plating showed log CFU decreased 4.5 fold in a dose-response manner from 0.0 to 2.5kGy; the organism was not viable beyond a 2.5kGy radiation exposure. qPCR showed consistent A. flavus presence across doses with a mean of 7.04 ± 0.34 log gene copies. AFB1 concentration did not significantly change with increasing doses of radiation. HPLC data showed a mean AFB1 concentration of 240.22 ± 17.66ppb. ELISA data showed a mean AFB1 of 267.08 ± 53.59ppb. Our results imply that X-ray irradiation is an effective means of rendering A. flavus non-viable in maize materials without affecting AFB1 concentrations. This finding is important because pre-sterilizing maize for lab-based mycotoxin studies reduces the hazard of fungal spores spreading and possibly contaminating other experiments in indoor shared laboratory spaces.