Effect of sugars and growth media on the dehydration of Lactobacillus delbrueckii ssp. bulgaricus

AIMS: The efficiency of trehalose, sucrose and maltose to protect Lactobacillus bulgaricus during drying has been evaluated in bacteria grown at low water activity. METHODS AND RESULTS: Bacteria were grown in MRS (control), and in MRS supplemented with sucrose (MRS-sucrose) or with polyethyleneglycol (PEG) (MRS-PEG) as low water activity media. The growth in low water activity media (MRS-sucrose and MRS-PEG) prior to drying enhanced the effectiveness of trehalose as thermoprotectant during drying. The efficiency of sucrose was improved when bacteria were grown in MRS-sucrose. On the other hand, the growth in both low water activity media did not affect the efficiency of maltose. The damage produced during dehydration has been evaluated by means of growth kinetics in milk. The preservation of bacteria dehydrated with sucrose, after growing them in MRS-sucrose, appears to be as efficient as the dehydration with trehalose. CONCLUSIONS: The growth of L. bulgaricus in low water activity media enhances the protective action of trehalose and sucrose. SIGNIFICANCE AND IMPACT OF THE THE STUDY: These results may aid the dairy industry to improve the recovery of the starters at low costs after preservation processes.