Inhibition of Aspergillus carbonarius and fungal contamination in table grapes using Bacillus subtilis

•Bacillus subtilis had significant growth inhibition of Aspergillus carbonarius in vitro and in vivo.•B. subtilis had significant growth inhibition of fungal contamination in table grape.•Both B. subtilis liquid and cell-free culture supernatant have inhibitory effect.•The inhibition effect of B. subtilis was diversity among different grape cultivars.

Aspergillus carbonarius is a major producer of ochratoxin A in grapes, causing fungal decay and posing a significant threat to human health. Bacillus subtilis CCTCC M 207209 was used to inhibit the growth of A. carbonarius CCTCC AF 2011004, an ochratoxin A-producing strain previously isolated from grapes. The inhibition effect in vitro was tested in potato dextrose agar medium (PDA), while in vivo effects were examined in grape berries of three different grape cultivars: Thompson Seedless, Kyoho, and Red Earth. Inhibitory effects were evaluated according to colony size in PDA and rotten spots in grape berries when A. carbonarius and B. subtilis were inoculated simultaneously and cultivated at 0 °C, 25 °C, or 30 °C. B. subtilis liquid cultures with and without cells and volatile products were used in the analyses. Significant inhibition of A. carbonarius was observed in all samples treated with B. subtilis liquid cultures, especially those subjected to cell-free culture treatment. No inhibition was observed for A. carbonarius treated with the volatile products of B. subtilis. The inhibition was the most significant in Red Earth grapes, followed by the Kyoho then Thompson Seedless varieties, when the same fraction of B. subtilis culture was used. Significant inhibition was also observed for other fungal contaminants in grapes when B. subtilis liquid culture supernatant was used. This study reveals the potential of B. subtilis for inhibiting contamination of OTA-producing A. carbonarius and other fungi in table grapes.