CELLULAR DAMAGE AND STORAGE STABILITY OF LACTOBACILLUS RHAMNOSUS GG DRIED IN DISACCHARIDE MATRICES UNDER VACUUM
The survival of cell concentrates of Lactobacillus rhamnosus GG (LGG) in selected dissacharides after drying under vacuum was evaluated. Drying is a useful technique for preserving foods, agricultural products and pharmaceuticals. However, biological materials can be irreversibly damaged during this treatment resulting in substantial loss of viability and activity. In this paper, disaccharide systems (trehalose, sucrose and lactose) were used as protectants for L. rhamnosus GG. Among the solutes examined, trehalose improved the recovery of viable cells after drying as well as during storage at 4°C and 25°C. Stored vacuum-dried trehalose systems were found as viscous syrups which indicated that they were not glassy. Damage of cell membrane and reduction in colony sizes occurred as a result of dehydration inactivation. Comparison of the conventional techniques with flow cytometric viability assessment after drying revealed the occurrence of certain cell population which were stressed and lost their ability to grow on agar. The protecting ability of trehalose on bacterial cells was only against lysozyme and pepsin actions. These results could have some relevance, especially in underdeveloped and /or developing countries, for the production of functional confections.