Spray-drying process as a suitable tool for the formulation of Bacillus velezensis RC218, a proved biocontrol agent to reduce Fusarium Head Blight and deoxynivalenol accumulation in wheat

Abstract

ABSTRACTFusarium Head Blight is a worldwide disease affecting small grain cereals. Among the different management strategies, biocontrol is an environmentally-friendly approach to counteract this disease. Biocontrol effectiveness of Bacillus velezensis RC218 was demonstrated under greenhouse and field trials, but formulation conditions were not specified. Bacillus velezensis RC218 was grown on a sucrose and yeast extract basal medium (control) and in the same medium osmotically modified with NaCl to reach a 0.98 and 0.97 aW for physiological improvement. Before spray-drying process, MgSO4 (10% w/v) was added to the cells as a protective agent. Water, phosphate buffer and skimmed milk (10% w/v) were evaluated as rehydration agents. Shelf-life of the product was evaluated during 180 days at different storage temperatures (4°C and 25°C). The viability of control cells after the drying process decreased from 3.2 × 108 to 1.12 × 106 colony forming units per gram of dry weight (cfu/g dry w), meanwhile cells grown in stressed media retained a viability of 5 × 106 cfu/g dry w. Water and phosphate buffer resulted in the best rehydration agents. After 180 days, the best storing condition was observed for cells grown in NaCl at 0.97 aW and stored at 4°C, =4 × 106 cfu/g dry w, 80% of the initial viability. Spray drying was found to be a good method for conserving long term shelf-life of B. velezensis RC218 dried cells.