Environmental Effects on the Efficacy and Microflora of Hermetically Stored Maize

Maize is a vital component in the diet of people in many countries in Sub-Saharan Africa, consisting of nearly a third of daily calorie consumption. However, improper drying, insect colonization and the growth of mycotoxigenic fungi often leads to spoilage of the grain, making it unfit for consumption. In recent decades, hermetic storage has been demonstrated to be an effective means for the safe storage of grain. Hermetic bags create an air-tight barrier to limit the exchange of oxygen, carbon dioxide, and moisture. This causes the death of insects and reduces fungal growth. However, results conflict on the efficacy of hermetic storage for the prevention of fungal growth and accumulation of mycotoxins under environmental conditions. To answer this question, an experiment was established in Indiana and Arkansas for the storage of grain under diverse environmental conditions. The objectives of this study were to provide evidence that hermetic storage prevents the quality and quantity loss of grain, and to characterize the microbial biome of stored maize through the use of high throughput sequencing. In this experiment, Hermetic Purdue Improved Crop Storage (PICS) bags and non-hermetic woven bags containing 40 kg of maize harvested the previous fall were stored through the months of July-September in 2015. The bags were exposed to daily fluctuations in temperature and relative humidity. Results indicate that hermetic bags prevent the ingress of moisture and rewetting of grain under environmental conditions. The warmer environment of Arkansas contributed to extensive colonization of the woven bags by insects and infiltration of the maize by storage fungi. Genera identified by plating included Gibberella, Aspergillus, Penicillium, and Alternaria. Results on the accumulation of aflatoxin in satchels of Aspergillus flavus remained unclear. The analysis of the microbial biome indicated that the genera identified through traditional plating were among the dominant genera in the high-throughput sequencing analysis. Our results indicated that thee microbial biome contained a large amount of fungal diversity. However the results suggest that the biome of the grain was fixed prior to commencement of the experiment and storage location or bag type had little impact on the diversity of the flora within the grain