• freeze-drying;
  • protective agents;
  • rehydration media;
  • survival rates;
  • viability


Aims:  The effects of different freeze-drying protective agents on the viabilities of biocontrol strains Bacillus cereus AR156, Burkholderia vietnamiensis B418 and Pantoea agglomerans 2Re40 were investigated.

Method and Results:  Several concentrations of protective and rehydration media were tested to improve the survival of biocontrol agents after freeze-drying. The subsequent survival rates during storage and rehydration media of freeze-dried biocontrol strains were also examined.

Conclusions:  The results indicated that cellobiose (5%) and d-galactose (5%) gave maximum viability of strains Bu. vietnamiensis B418 and P. agglomerans 2Re40 (98 and 54·3% respectively) while the perfect one (100%) of strain B. cereus AR156 was obtained with sucrose (5%) during freeze-drying, and the highest survival of the three strains was reached when they were rehydrated with 10% nonfat skim milk. In the following storage, the survival rates showed that B. cereus AR156 could still reach 50% after 12 months.

Significance and Impact of the study:  This study showed that freeze-drying could be used to stabilize cells of these three biocontrol strains. Further studies should focus on the scale-up possibilities and formulation development.