Comparison of spray-drying and freeze-drying for inoculum production of the probiotic Bacillus amyloliquefaciens strain H57

Spray and freeze drying practices for production of the probiotic Bacillus amyloliquefaciens H57 as a power for feed applications were investigated. The importance of inlet temperature, feed rate, solid content, and limestone, a heating protectant, concentration was demonstrated. Spray drying outlet temperature appeared to be crucial for survivability of B. amyloliquefaciens H57. Studying inactivation kinetics at 80, 90, and 100 degrees C revealed the highest D-value at 260.7 +/- 47.3 min at 80 degrees C before gradually declining with increasing temperature. By considering the D-value, a high survival rate of 100%, which was far superior to freeze drying at 60 +/- 4%, was obtained when the spray drying outlet temperature was maintained at 80 degrees C with 175 +/- 2 degrees C inlet temperature, 20.9 +/- 0.4 mL min(-1) feed rate, 20% solid content, and 1:0.3 ratio of dry mass of the probiotic material to limestone. After 50-days of storage, significant differences in the viability of B. amyloliquefaciens H57 were observed between the powders obtained by the two drying methods. Storage temperature had a substantial impact on the probiotic stability. Best viability retention was spray dried powder stored at 4 degrees C. This work demonstrates that spray drying can be an effective method for producing a functional probiotic and highlights its potential for applications in feed supplement manufacturing. (C) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.