J. Gen. Appl. Microbiol., 50, 107–114 (2004)

industrial applications. Advantages of immobilized cell technology include continuous utilization, retention of plasmid-bearing cells, prevention of interfacial inactivation, stimulation of production and excretion of secondary metabolites, and protection against turbulent environment (Melzoch et al., 1994; Nath and Chand, 1996; Tramper, 1990). Potential applications of immobilized cell technology in the dairy industry have been widely examined (Champagne et al., 1994). Some novel processes with immobilized cell technology for the continuous inoculation of milk for yogurt or cheesemaking have been suggested which constitute modern improvements of traditional batch processes. Immobilization of cells will lead to effective enhancement of cell concentration and survival and increase of process efficiency (Groboillot et al., 1994). For fulfillment of that purpose the cell loading in immobilized preparations is one of the most important factors. Many immobilization techniques for lactic acid bacteria have been examined, but no cell loading above 5 10 cfu/g gels has been reported (Champagne et al., 1994; Lamboley et al., 2003). Cell immobilization has been examined extensively in the freeze-drying and storage thereafter of lactic acid bacteria, and significant improvement in survival could be obtained and cell concentration of dried samples could be raised (Champagne et al., 1996; Kornacki and Gabis, 1990; Maitrot et al., 1997; Tsen et al., 2002). Damage to cells caused by freezing might also be reduced by immobilization (Champagne et al., 1992). At the same time, cell immobilization of lactic acid bacteria by gel entrapment could effectively increase their tolerance to bile acid and gastric juice and promote their survival and activity in human intestinal tracts (Lee and Heo, 2000; Sun and Griffiths, 2000). The aim of the present research is to obtain immobilized preparations of thermophilic and mesophilic lactic acid bacteria and their symbiotic culture with high cell loading (concentration of living cells higher than 10 cfu/g) and to investigate the survival and cell concentration in freeze-drying preparations and subsequent storage. In the investigation the following strains of lactic acid bacteria (LAB) were used: Lactobacillus delbrueckii ssp. bulgaricus BTCC 3598, Lactobacillus casei BTCC 3364, Lactococcus lactis 1375/CHR (Hansen Laboratorium, Denmark) and Streptococcus thermophilus BTCC 3597. Liquid medium LAPT g 10 (Peral de Portillo et al., 1988) was used for both freely suspended and immobilized cells culture (g/dm): peptone—15.0, tryptone—10.0, yeast extract—10.0, Tween 80—1.0, glucose—10.0, pH 6.6. For solid medium 10 g/dm agar-agar was added. Immobilized lactic acid bacteria for application as dairy starters and probiotic preparations