Biocontrol products based on Bacillus amyloliquefaciens CPA-8 using fluid-bed spray-drying process to control postharvest brown rot in stone fruit

Two products based on the biocontrol agent Bacillus amyloliquefaciens CPA-8 have been developed as an effective alternative to chemical applications to control postharvest brown rot in stone fruit. As part of the production and formulation processes, the effects of three different nitrogen sources on growth media and the effects of different carrier materials and protectants on fluid-bed spray-drying were studied. CPA-8 populations achieved 109 CFU/mL after 72 h of culture. However, the protein PROSTAR 510A at 20 g/L provided better growth curves compared to the boiled extract from Defatted Soy Flour and protein PROSTAR 510A at 10 g/L. Furthermore, culture ages of 72 h were needed to obtain high endospore production and therefore, suitable heat tolerance of CPA-8. The use of the protectants 20% sucrose plus 10% skimmed milk resulted in the best formulations when either carrier material, maltodextrin or potato starch, was used. These two products were then selected for assays of shelf life and efficacy. CAP-8 viability was unchanged after 15 months of storage at 4 and 22 °C, maintaining concentrations between 7.8 × 109 and 1.2 × 1010 CFU/g. Finally, the efficacy of the CPA-8 products against Monilinia spp. was confirmed (>44.4% disease reduction) on peaches, nectarines, flat peaches, cherries, apricots and plums.

This research was supported by the European projectBIOCOMES FP7-612713 and by the Catalan government (Generalitat de Catalunya) for the PhD grant 2014-FI-B00367 (Amparo M. Gotor). The authors also thank CERCA Program (Generalitat de Catalunya) and the technical and logistical support provided by Cèlia Sánchez and Andrea Berge.