Effect of protective agents, rehydration media and initial cell concentration on viability of Pantoea agglomerans strain CPA-2 subjected to freeze-drying
E. Costa et al., Effect of protective agents, rehydration media and initial cell concentration on viability of Pantoea agglomerans strain CPA-2 subjected to freeze-drying, J APPL MICR, 89(5), 2000, pp. 793-800
The effect of initial cell density, protective agents and rehydration media
on the viability of biocontrol agent Pantoea agglomerans CPA-2 when subjec
ted to freeze-drying was studied. Several additives were tested as protecti
ve agents against freeze-drying injury. Maximum viability of the bacterial
cells was obtained with disaccharides (survival levels > 60%). Freeze-dried
samples were rehydrated with several media; the highest percentage viabili
ty was obtained with 10% non-fat skim milk (100%+). The effect of initial b
acterial load on the final recovery was dependent on protectant but not on
rehydration media. Sucrose was an effective protectant when a high initial
concentration (10(10) cfu ml(-1)) was used; the opposite occurred with non-
fat skim milk. The use of 10(10) cfu ml(-1) as an initial concentration, su
crose as a protectant and non-fat skim milk as a rehydration medium enabled
100% of P. agglomerans viability to be conserved after freeze-drying. Resu
lts suggest the possibility of achieving a good formulation system for the
studied biocontrol agent with a high number of viable cells to be used towa
rd pathogens, which is desirable for the industrial development of the prod
uct.