Bacillus amyloliquefaciens UTB96, an effective biocontrol and aflatoxin- degrading bacterium

Aspergillus flavus grows on a wide range of agricultural and food products and causes contamination with aflatoxin. One of the suitable methods for controlling aflatoxin is the use of biological agents, which is possible by the application of effective bacterial antagonists. The objectives of the present study were to isolate and characterize a superior biocontrol agent against the above-mentioned fungus on pistachio, to develop an industrial culture medium and to optimize its growth conditions for enhancing maximum biomass production for Bacillus amyloliquefaciens UTB96. According to the results, this strain was capable of significant growth inhibition of A. flavus and reducing aflatoxin concentration in the pistachio up to 98.38%. Moreover, its VOCs showed growth inhibition as well. The most effective environmental factors were screened using the Bremenplacket design, in terms of their effects on the biomass production of the antagonistic bacterium and optimizing the production of bacterial biomass in culture medium designed using the screened factors. The results showed that sugarcane molasses and corn steep could be used as the industrial sources of carbon (C) and nitrogen (N) in production at 10 and 2 g/l respectively. Optimum conditions for maximum production of biomass in this culture medium included pH=7, 30°C and C/N ratio 1:23. Using the optimized culture medium and conditions in a semi-industrial method, the amount of biomass was reached up to 0.17 g/l, and the antagonistic effects increased by 8%. Bacillus species used in this work shows some similarities with B. velezensis that needs to be validated by further molecular analysis.