Survival of Pantoea agglomerans strain CPA-2 in a spray-drying process

Spray drying could be a suitable method for preserving microorganisms, as it allows large quantities of cultures to be dried at low cost. The aims of this paper were to evaluate the effects of spray-drying conditions on survival of the biocontrol agent Pantoea agglomerans CPA-2, which has shown antifungal activity against Penicillium expansum and Penicillium digitatum on citrus fruits. Various compounds cited in the bibliography as carriers were tested in our spray drying, and some salts (MgSO4, K2SO4. and Na2CO3) and dairy products (lactoserum or nonfat skimmed milk [NFSM]) showed the best results in terms of recovered powder. Outlet temperature had more influence on the death of bacteria than inlet temperature. P. agglomerans was heat sensitive, and the activation energy was around 6 kcal/mol K when MgSO4 (10%) or NFSM (10%) were used as carriers and only 3 kcal/mol K when the combination of MgSO4 (10%) and NFSM (10%) was used. The highest powder recovery was obtained when NFSM was used as the rehydration medium. Although the percentage of powder recovery was not high (around 50%) and viability was low, the results suggest that with bigger spray dryers, we could expect a lower outlet temperature and probably an increased viability. Further research into spray-dryer design is needed in order to demonstrate this.