Effect of Added Carbohydrates on Membrane Phase Behavior and Survival of DriedLactobacillus plantarum

Protective effect of sorbitol and monosodium glutamate during storage of freeze-dried lactic acid bacteria

“…Similar results were obtained by Fonseca et al [7], who have shown that there is no effect of glycerol during freezing of Streptococcus thermophilus, although a positive effect was observed during frozen storage. Substantial increases in residual activity and viability after drying, following addition of sorbitol to the drying medium, have been reported [1,17] for various organisms, although there is not a general consensus [8]. Damage to biological systems derived from freeze-drying has been attributed to two primary causes: (i) changes in the physical state of the membrane lipids, and (ii) changes in the structure of sensitive proteins in the cell [15].…”

“…Damage to biological systems derived from freeze-drying has been attributed to two primary causes: (i) changes in the physical state of the membrane lipids, and (ii) changes in the structure of sensitive proteins in the cell [15]. The mechanisms underlying sorbitol protection of dried cells would thus be: (i) prevention of damage to the membrane via interaction therewith [16], and prevention of lipid oxidation owing to its anti-oxidant properties [17]; (ii) stabilisation of protein structure, and hence preservation of functionality associated with the formation of sorbitol-protein complexes [25]; and (iii) maintenance of turgor, owing to the accumulation of said additive [24].…”

“…Damage to biological systems resulting from freeze-drying can be attributed mainly to changes in the physical state of membrane lipids and changes in the structure of sensitive proteins [15]. Consequently, a number of studies have examined the potential role of additives in suspensions of microorganisms, such as sugars, polyols, amino acids, peptides and proteins, in their survival throughout freezing and drying [1,7,8,[14][15][16][17]24]. However, even if survival is observed during freezing and/or drying, viability may be lost afterwards during the storage process, which thus hampers the final goal of those preservation technologies.…”

“…A good protectant should provide cryoprotection of cells during freezedrying, be easily dried, and provide a good matrix to allow stability and ease of rehydration [4]. Sorbitol and monosodium glutamate (MSG) have been reported as efficient protectants [1,11,17,22]. An increase in residual activity and viability during drying following the addition of sorbitol to the drying medium has been previously reported for various organisms [1,17].…”

“…Sorbitol and monosodium glutamate (MSG) have been reported as efficient protectants [1,11,17,22]. An increase in residual activity and viability during drying following the addition of sorbitol to the drying medium has been previously reported for various organisms [1,17]. Although the mechanism of protecting living cells by polyols is not fully understood, three hypotheses have been proposed so far that may be involved in cell protection [24]: (i) maintenance of turgor, resulting from the accumulation of mannitol at low water activity [13]; (ii) stabilisation of the structures of membrane lipids and proteins at low water activity [15,25]; and (iii) prevention of oxidative damage by scavenging of free reactive oxygen radicals [15].…”