Enhancing spray-drying tolerance of Lactobacillus bulgaricus via non-sporeforming dormancy induction

Employing 0.64 mg/mL of rifampin (RFP) for dormancy induction of Lactobacillus bulgaricus sp 1.1, a 2.5-fold survival rate was achieved after spray drying, while the dried bacteria displayed delayed acidifications. Under the same condition for dormancy treatment, division analysis indicated that high proportions of cells would enter into a dormant state with around 90% of non-proliferating bacteria in the original population. Cells shrank with median diameters decreasing from 3.23 to 2.98 μm. The Raman spectrum revealed a lower ATP level, varied protein expression profiles and conformations and saccharides accumulation in bacteria. Protein aggregates formed in dormancy-induced cells may contribute to increased heat resistance which showed a 2 °C rise in the denaturing temperature in the 0.64 mg/mL group. Therefore, dormancy treatments may be developed as a protective strategy for spray-dried L. bulgaricus.