Optimization of packaging and storage conditions of a freeze-dried Pantoea agglomerans formulations for controlling postharvest diseases in fruit

AIMS: This study aimed to evaluate different packaging strategies to extend the shelf life of a freeze-dried formulation of the biocontrol agent Pantoea agglomerans strain CPA-2. METHODS AND RESULTS: Different materials and atmosphere packaging conditions (vacuum and air) were analysed on formulated P. agglomerans cells stored at 25, 5 and -20°C. Results showed the viability of CPA-2 cells stored at 5 or -20°C was significantly higher than when stored at 25°C. The highest viabilities were observed with the plastic material designated as Bottle 1, in nonvacuum packaging in all storage temperatures: 50% after 3 months at 25°C, 100% after 8 months at 5°C and 100 and 74% after 12 and 18 months, respectively, at -20°C; the final concentration was 10(12) CFU g(-1), a good concentration for a commercial product. The efficacy to control blue and green mould on apples and oranges, respectively, of these packed and stored cells was similar to fresh CPA-2 cells. CONCLUSIONS: This work showed a suitable packaging strategy for a freeze-dried formulation of the CPA-2, providing a good shelf life and efficacy against the major postharvest diseases of apples and citrus based on a plastic bottle stored at cold or frozen storage conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: The last phase of the commercial development process for biocontrol agents is presented in this work. A bacterium-based product that ensures the efficacy, stability and easy application of the antagonist to control postharvest fungal diseases on fruit was successfully obtained.

This research was supported by the national project RTA2009-00053 (Plan Nacional de I + D Ministerio de Ciencia e Innovación, Spanish Government) and by a ‘Ramon y Cajal’ contract (R.T.). Authors are also grateful with the company BIODURCAL S.L. for providing some of the plastic bags used in this work.