Spray freeze-drying (SFD) is a comparatively new method of producing biopharmaceutical powder preparations.
In this study, Lactobacillus casei (IFO 15883) was spray freeze-dried to obtain a fine probiotic
powder. The survival rate of L. casei in the powder after the SFD process was measured using plate agar
counting. To improve the survival rate of L. casei during the SFD process, various experimental conditions
were carried out. Among five growth media compositions, in Lactobacilli MRS broth with 1% mannose and
0.1% CaCO3, the viability of the freeze-dried powder was not significantly different from that of the initial
powder (p > 0.05). The most effective air pressure and protective agent during SFD were 20 kPa and buffered
peptone water (BPW), respectively. Scanning electron microscopy (SEM) was applied to estimate
the physical structure and properties of the particles. SFD probiotic particles were of various shapes
and sizes with porous structures under different SFD conditions. The average diameter of optimized
probiotic powder particles with annealing was 24.8 lm. The survival rate of the final SFD probiotic
powder under conditions was 97.7%.