Induction of stress tolerance in Lactobacillus delbrueckii ssp. bulgaricus by the addition of sucrose to the growth medium

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The lactic acid bacteria (LAB) play an important role in the production of fermented foods. The development of concentrated cultures of LAB, for inoculating the production vat directly (bulk starters), has eliminated many problems traditionally involved in their preparation and maintenance by the food industry. For industrial use, LAB are often preserved in a frozen or dried form, the latter preparations having lower transport and storage costs (Kets et al. 1996). Dried cultures, however, lose viability/activity during storage, especially when kept at room temperature (Champagne et al. 1991; Teixeira et al. 1995a,b; Castro et al. 1996). Attempts to improve the survival of LAB during drying have already been tried (Linders et al. 1997b; Gardiner et al. 2000). Previous results indicated a direct relationship between the presence of compatible solutes in LAB and their ability to survive drying conditions. Such solutes include amino acids, amino acid derivatives, quaternary amines, sugars and tetrahydropyrimidines (Kets & De Bont, 1994; Kets et al. 1994, 1996).