Enhancing the Viability of Lactobacillus plantarum Inoculum by Immobilizing the Cells in Calcium-Alginate Beads Incorporating Cryoprotectants

Abstract

Many literature reports have cited the importance of the rehydration conditions of lyophilized cultures in determining viability. The rate of rehydration and the volume of fluid used have been identified as two important factors. One possible means of controlling these is by immobilizing the cells before lyophilization within a gel matrix in which the subsequent rehydration rate and fluid volume would be controlled by the properties of the gel. In this study Lactobacillus plantarum was immobilized and lyophilized in Ca-alginate beads in which 1 M glycerol or 0.75 M adonitol with skim milk were incorporated as a cryoprotectant. The properties of these Ca-alginate beads were examined before and after lyophilization and rehydration. The beads incorporating glycerol were smaller and stronger than those with adonitol. After lyophilization, size decreased and strength increased but to a greater extent in the beads with glycerol, indicating that the microenvironment within the two bead types was probably different. The protective effect of the bead microenvironment on immobilized L. plantarum was also examined. Lyophilization and rehydration within the alginate beads with either polyol yielded higher survival rates than that attained with free cell cultures during rehydration in optimal or suboptimal conditions. During rehydration under suboptimal conditions, the immobilized cell survival was greatest when 0.75 M adonitol was the incorporated cryoprotectant.

Growth characteristics of agrowaste‐immobilised lactobacilli in soymilk during refrigerated storage

“…Wheat grain, which is high in dietary fibres, was found to provide immobilisation support that enhanced the viability of lactic acid bacteria (Bosnea et al, 2009). Additionally, sugars such as glucose, fructose, lactose, mannose, sorbitol, inositol, sucrose and trehalose have been found to exert a protective effect on proteins and cell membranes (Kearney et al, 1990). Higher concentration of sugars in the media in conjunction with cell immobilisation had been suggested to synergistically contribute to the stability of lactic acid bacteria under extreme conditions (Zayed & Roos, 2004).…”

Effect of protective solutes on leakage from and survival of immobilized Lactobacillus subjected to drying, storage and rehydration

“…Adonitol, which cannot be metabolized by most lactobacilli, has shown a protective effect during freeze-drying by controlling the water content (Valdéz et al 1985a;Kearney et al 1990). This may be due to the steric conformations of its hydroxyl groups which may replace water molecules in protein structures (Valdéz et al 1983b).…”

“…Skim milk is expected to prevent cellular injury by stabilizing the cell membrane constituents (Valdéz et al 1983b;Kearney et al 1990;Castro et al 1995). Calcium in milk increases survival after either freezing or freeze-drying (King and Su 1993).…”

“…Among several others, adonitol, betaine, glycerol and skim milk have been reported as efficient suspending agents for freeze-drying or convective drying of bacterial cells (Sinha et al 1974;Valdéz et al 1983aValdéz et al , 1983bValdéz et al , 1985aBarbour and Priest 1986;Kearney et al 1990;Selmer-Olsen et al 1996).…”

Preservation of Chitinolytic Pantoae agglomerans in a Viable Form by Cellular Dried Alginate‐Based Carriers

“…Better recovery is generally achieved when the bacteria are immobilized and cryoprotective agents are added. Various groups of substances have been considered for their possible protective action, including glycerol and other polyols, polysaccharides, disaccharides, amino acids, proteins and their hydrolysates, minerals, salts of organic acids, and vitamin-complex media (7)(8)(9). In most cases, survival after freeze-drying does not exceed 86% and 3% for Gram-positive and Gram-negative bacteria, respectively (1,2,(8)(9)(10)(11)(12).…”