Formulation of the microbial agent Bacillus amyloliquefaciens NCPSJ7 and its application against Botrytis cinerea in tomato

Spray drying was used to prepare the bacterial powder of Bacillus amyloliquefaciens, which was then used for wettable reagent production. The biocontrol effects of the microbial agent B. amyloliquefaciens against Botrytis cinerea on tomatoes were studied for pre- and postharvest applications. Single-factor analysis was performed to optimize the factors that may affect the bacterial concentration during spray drying, including inlet temperature, feed rate, airflow rate, wall materials, and their concentrations. The parameters were established as follows: inlet temperature of 170 °C, feed flow rate of 360 mL/h, airflow rate of 30 m³/h, and 10% maltodextrin. The agent with a concentration of 11.30 log colony-forming units (cfu)/g was obtained. The prepared wettable bacterial powder showed significant inhibitory activities against the tested pathogenic fungi, including Fusarium oxysporum, Alternaria alternata, Aspergillus niger, and B. cinerea. After harvest, the tomatoes were sprayed with the prepared microbial agent. The bacterial spores colonized the surface of tomatoes, which prevented B. cinerea from infecting the tomatoes effectively by competition for space and parasitism. The preharvest tomatoes were sprayed with the prepared microbial agent at a dose of 8.1 × 10⁷ cfu/mL, which showed an equivalent biocontrol effect to procymidone. Preharvest spray could prolong the storage period and reduce the rotting rate of tomatoes during storage. In conclusion, an efficient and stable B. amyloliquefaciens agent can be prepared by spray drying, which then can be used to control B. cinerea disease pre- and postharvest.