Effect of disaccharides on the preservation by drying of lactobacillus bulgaricus grown at low water activities

TYMCZYSZYN, E.; DISALVO, A.

Mar del Plata– Buenos Aires – Argentina

Congreso; ISOPOW 2004 - IX International Symposium on the Properties of Water; 2004

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 previous works, (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 trehalose, sucrose and maltose, at different concentrations in bacteria grown at low water activity. 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 70º 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. The growth in low water activity does not enhance the recovery after drying, but helps to increase the number of survivors in the presence of sugar. This would indicate that these cells would not accumulate osmolytes during the growing at low water activities nor than the metabolic changes are sufficient to prevent damage by drying. Nevertheless the presence of sugars is vital for the recovery, and the growth at low water activity favors the cells-disaccharides interaction.