Study On Fungal Diversity And Mycotoxins From Corn And Wheat During Storage

The species and abundance of fungi mycotoxins of grain influence quality and safety of cereal products directly. Thus, it’s significant to know enterotoxigenic fungal diversity and accumulation regularity of mycotoxins. In my paper, the raw materials were wheat and corn.The fungal diversity of the grain under different storage conditions were analyzed using Simulating storage environment, proportion of bacteria, PCR-DGGE, HPLC and so on.Abundance of fungi and accumulation regularity of mycotoxins also were studied. In order to research the changing pattern of total microbial abundance and the quality of the wheat during storage, the wheat was treated by combined antifungal agents and compound antimicrobial agents, and then we established a fast and efficient multiplex PCR detection system for three kinds of toxoggenic fungi. The results showed that:1. The corn with initial moisture content of 12.42%, 14.30%, 15.89%, 17.62% and19.88% was storaged at 30 ℃and 75%, 84% and 92% relative humidity for 35 days. The growth of aspergillus flavus and toxin-producing was inhibited by other microorganisms in the medium and high humidity condition. Corn was stored for 35 days at 30 ℃ and 75%relative moisture. the total number of aspergillus flavus and aspergillus Niger was very significant positive correlation with aflatoxin B1(P<0.001,k≥0.997). The total number of aspergillus Niger on the corn was significant positive correlation with aflatoxin B1 at 30 ℃and relative moisture 75%(P<0.05, k=0.921).2. The corns with initial moisture content of 12.42%, 14.30%, 15.89%, 17.62% and19.88% were stored at 30 ℃ for 28 day, and their relative humidity(RH) were 75%, 84%and 92% respectively. In the low humidity environment, the relationship that trichoderma viride suppress the zearalenone was affected by initial moisture content significantly, and it increased rapidly with the initial moisture increasing. The zearalenone was strongly inhabited by trichoderma viride rather than initial moisture at the medium and high humidity condition.Corn was stored at 30 ℃ and 75% relative moisture for 28 days. The number of fusariummoniliforme was negative correlation with the zearalenone, so it was with trichoderma viride and mould. For 92% relative humidity, the numbers of mould, trichoderma viride and fusarium moniliforme were positive correlation with the zearalenone, especially fusarium moniliforme(P<0.05). The trichoderma viride and water component was significant positive correlation with zearalenone(P<0.05) at relative humidity of 84%. The number of mould and fusarium moniliforme was negative correlation with the zearalenone, respectively. The result showed that zearalenone was strongly influenced by biological and environmental factors at the medium and low humidity condition. Moreover, the zearalenone was strongly influenced by fusarium moniliforme at high humidity condition.3. The wheat was dealt with potassium sorbate, sec-Butylamine and natamycin with different proportions at 30 ℃ and reality humidity(RH) for 35 days. The inhibition efficiency to Aspeigiulls and mould of combination of Natamycin and potassium sorbate increased 942 3 and 7 times than control group. We found the optimal mixed ration was 0.015 g natamycin and 1.00 g potassium sorbate per 1 kg wheat. The wheat viscosity indexes included peak viscosity,minium viscosity,final viscosity,pad value and setback, and they were positively correlated with fungal abundance. Meanwhile, the amount of fatty acids was significantly positively correlated with fungal abundance(P<0.05).4. The wheat was dealt with potassium sorbate, sec-Butylamine and Nisin with different proportions at 30 ℃ and relative humidity 75% for 35 days. We found the optimal mixed ration was 0.20 g Nisin, 1.00 g potassium sorbate and 2.00 g 2-aminobutane per 1 kg wheat.The counts of fungi, Aspeigiulls, Penicillium, Bacillus and bacterial were positively correlated with the amount of fatty acids and the total acidity values, and negatively correlated with the precipitation value.5. With specific primers for Aspergillus flavus, Aspergillus fumigates and Fusarium, a fast and efficient multiplex PCR detection system for three kinds of toxoggenic fungi was established. The limit of detection was about 6.00×10-6 μg/μL for Aspergillus flavus, 2.08×10-5μg/μL for Aspergillus fumigates and 1.10×10-5 μg/μL for Fusarium, respectively. This multiplex PCR detection system was high specific and stable. The detection time was less than 3 h.