Résumé
The viability of freeze-dried cells of Streptococcus thermophilus and Lactobacillus plantarum by adding different stabilizer and protectants such as skim milk, sucrose and trehalose were investigated. When the bacteria were dried with 150mmol/L trehalose,75% of S. thermophilus and 33% of L. plantarum cells were survived, comparing with control of 19% and 1% respectively. When S. thermophilus was exposed at 90℃, the cells with trehalose increased tolerance to high temperature. When S. thermophilus freeze-thawing for 4 and 8 cycles, the survival was much higher than that of without trehalose protected. Scanning Electro-microscope pictures showed that the cells with trehalose, appeared as normal, but those without the sugar were broken or collapsed. The data confirmed that the disaccharide could protect bacteria against stress conditions.