Drying of Lactobacillus bulgaricus growing at high osmolarity in presence of disaccharides

EMMA TYMCZYSZYN AND ANÍBAL DISALVO

Water Properties of Food, Pharmaceutical, and Biological Materials

CRC Press

Lugar: Boca Raton, Florida.; Año: 2006; p. 463 - 470

Abstract: Lactobacillus bulgaricus is a probiotic bacterium widely used in the milk industry. The preservation of lactic acid bacteria by spray-drying is of technological interest, since it implies low costs of production and storage. In a previous work, (Gomez Zavaglia et. al. 2003), we showed the protective effect of trehalose on these bacteria, dried under vacuum at 70ºC, for 30 minutes. In the present work, we compare the protective effect, of different concentrations, of trehalose, sucrose and maltose, in bacteria grown at low water activities. For this purpose, cells were grown in MRS broth supplemented with Polyethylene glycol or sucrose at 33 mosm and harvested at the stationary state. Then, bacteria were dried under vacuum at 70ºC for 30 minutes, in the presence and absence of the different sugars. This study demonstrates that sucrose and maltose are less effective than trehalose at low concentrations, but at 400 mM the recovery rate after drying was within the same order for the three sugars. The growth in low water activity does not enhance the recovery after drying. However it helps to increase the number of survivors after drying in the presence of sugar. This suggests that these cells do not accumulate osmolytes during the growing at low water activities, or that the metabolic changes are not sufficient to prevent damage by drying. Nevertheless the presence of sugars is essential for the recovery, and the growth at low water activity favours the cell-disaccharides interaction.