Investigation and application of Bacillus pumilus QBP344-3 in the control of Aspergillus carbonarius and ochratoxin A contamination

Abstract

This study was designed to investigate the antifungal activity of Bacillus pumilus 344-3 against toxigenic fungi. In vitro co-incubation assay revealed that A. carbonarius AC82, A. niger AN8 and P. digitatum PD43 are most sensitive fungi to bacterial antifungal compounds with zone of inhibition of 29.2 mm, 27.7 mm and 27.1 mm, respectively. The addition of Bacillus pumilus 344-3 culture supernatant at low concentration in the fungal growth medium stimulated A. carbonarius biomass, but inhibited ochratoxin A (OTA) synthesis significantly (p ≤ 0.05). Conidial germination of A. carbonarius was not affected in a medium containing 10% and 20% of the bacterial culture supernatant, while it was completely inhibited in 100% bacterial extract. Storage of bacterial culture supernatant at temperature ranging from −20 °C to 100 °C for 1 h, didn't affect its antifungal potential. In vivo application of bacterial extract on the maize kernels, showed 95% protection against A. carbonarius infection. Application of B. pumilus 344-3 culture supernatant on the surface of maize kernels provided 99% reduction in OTA production potential of A. carbonarius AC82. Because of its strong activities against the growth of A. carbonarius AC82 and OTA-synthesis, B. pumilus 344-3 can be considered as a very promising biocontrol agent.