Using microplasma-based lamps to fight PHL in cereal

Cereal crops are a main source of nutrition for humans and animals worldwide. However, they are hard-hit by postharvest losses (PHL). Filamentous fungi are a major cause of cereal PHL.

Doctoral student Zhenhui Jin and his advisor Dr. Yi-Cheng Wang are trying to address fungi-related cereal PHL issues using microplasma-based lamps that emit 222 nm far ultraviolet C (far-UVC) irradiation.

The researchers chose two fungi species, Aspergillus flavus and Fusarium graminearum, and two cereals, corn and wheat, to evaluate their lamps’ antifungal efficacy. The reasons for these choices were that 1) corn and wheat currently rank first and third in the world as staple foods, and 2) both are susceptible to fungi-related postharvest losses. Fusarium head blight is a notorious yet common disease in wheat, mainly caused by F. graminearum, which results in quality loss and mycotoxin accumulations, threatening human and animal health and costing more than $300 million per year in the United States alone. Corn, meanwhile, is the major target of A. flavus, and when infected can pose severe health threats to consumers as well as economic burdens to society as food quality diminishes.

Over the past two years, Mr. Jin has designed and optimized the above-mentioned far-UVC treatment systems and conducted experiments aimed at testing their antifungal efficacy against the two selected fungal strains. Specifically, he designed a 2D treatment frame and a 3D treatment chamber for the experiments, and used them to confirm that the microplasma-based lamps can effectively kill fungal conidia and inhibit mycelial growth in both A. flavus and F. graminearum. Mr. Jin’s study of the mechanisms of the lamps’ antifungal effect revealed that 222 nm far-UVC light primarily kills fungal conidia by damaging their cell walls and by causing accumulations of reactive oxygen species (ROS) inside them, though some DNA damage was also observed.

Mr. Jin first inoculated corn kernels with A. flavus and wheat grains with F. graminearum respectively, and found out that within 15 minutes of treatment in the chamber, the quantities of both fungi were reduced by more than 90%. These results are comparable to those achieved in previously published experiments that used 254 nm UVC for the same purpose. It is also worth noting that 222 nm far-UVC irradiation had limited negative effects on grains: for example, their moisture content was not significantly lower post-treatment (p > 0.05). Overall, the team’s results so far imply that microplasma-based far-UVC irradiation can be developed into a workable approach to reducing fungal-related cereal PHL.