Growth and aflatoxin production by Aspergillus flavus isolated from poultry feed: effects of physicochemical factors and storage conditions

Abstract Background Aspergillus flavus is an opportunistic pathogen and a common contaminant of poultry feed. Inappropriate storage of feed leads to the growth of A. flavus followed by the production of aflatoxins. One-fourth of the world’s population is affected by aflatoxins. The presence of these toxins in feed not only results in economic losses but also causes considerable health concerns. Despite established regulations, challenges remain in understanding the specific environmental and nutritional conditions that promote aflatoxin biosynthesis. Moreover, ensuring the stability of aflatoxin standards used in analysis critical for accurate quantification. Results In the present study, A. flavus was isolated from poultry feed via the plate dilution method and conventionally identified based on its macroscopic and microscopic characteristics. The aflatoxin production potential was determined via TLC and HPLC. Toxigenic A. flavus isolates were confirmed via PCR using species-specific primers. Optimization experiments for growth and aflatoxin production were conducted under different physicochemical conditions (Temperature; pH; 1, 3 and 5% of the substrates; and wheat, maize, and rice). Finally, the stability of the aflatoxin was evaluated under different storage conditions (storage solvents/solids and vials of different colors). Among the forty samples, thirty-nine were positive for the genus Aspergillus . Among these, twenty-two were identified as A. flavus with different aflatoxin’s profile. In the growth optimization experiments, the highest mean biomass (8.84 ± 0.02 g) was produced by A. flavus at pH 6 and an incubation temperature of 22℃. The highest value (11,622.24 ± 0.45ng/mL) of AFB 1 was produced in SD broth (pH: 6) at 28°C. Moreover, Maize proved to be an ideal supplement for aflatoxin production. The stability of AFB 1 was greater than that of AFB 2 . The ideal solvents for AFB 1 and AFB 2 are chloroform and methanol respectively. Notably, the least reduction in AFB 1 was recorded in the amber- colored vials, whereas AFB 2 remained more stable in the opaque vials after six months of storage at 4 °C. Conclusion In conclusion, maize based feed was more favorable for aflatoxin production, highlighting the importance of appropriate storage conditions to prevent fungal growth and aflatoxin accumulation in feed. Additionally, storage conditions including both types of solvents and vials affect long term aflatoxin stability. Therefore, aflatoxin standards should be stored under optimal conditions to reduce degradation.