J. Gen. Appl. Microbiol., 48, 237–241 (2002)

can settle in the intestinal tracts and constitute an important part of the indigenous microflora of man and higher animals (Gomes and Malcata, 1999). It exerts a protective role by suppression of pathogenic microorganisms in the intestines and acts as a probiotic (Bergey and Holt, 1994; Gilliland and Speck, 1977; Sandine, 1979). On account of the disturbance of the proliferation and growth of L. acidophilus caused by antibiotic intake, digestive disorders, and abnormal and abusive food habits, dietary supplement of live L. acidophilus to maintain or ameliorate intestinal health might be beneficial and has been recommended (Brennan et al., 1983; Gilliland et al., 1978). Since the number of active cells in dried products is low (Brennan et al., 1983), attemps to improve the viability of L. acidophilus in commercial dehydrated products are required. Immobilized cells have been suggested for many industrial applications (Norton and Voillemard, 1994). Advantages of immobilized cell technology include continuous utilization, prevention of interfacial inactivation, stimulation of production and excretion of secondary metabolites, retention of plasmid-bearing cells, protection against a turbulent environment, etc. (Anselmo and Navais, 1992; de Backer et al., 1992; Melzoch et al., 1994; Nath and Chand, 1996). On the other hand, cell concentration could be effectively enhanced, and the survival and process efficiency could also be increased by the application of immobilized cells during operation (Champagne et al., 1994; Groboillot et al., 1994). Culture dehydration was normally carried out by freeze-drying which might bring about impairment to cells due to the freezing and succeeding treatment (Castro et al., 1996; Champagne et al., 1991; Heckly, 1978). This might also result in a decrease in culture survival during the subsequent storage (Bozoglu et al., 1987; Brennan et al., 1986). 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., 1992, 1996a; Kim et al., 1988; Maitrot et al., 1997; Yoon et al., 1995). Damage to cells caused by low-temperature and freezing might also be reduced by the application of cell immobilization (Champagne et al., 1992; Kearney et al., 1990). On the other hand, 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 objective of this research was to increase the survival and cell concentration of L. acidophilus in freeze-drying by the use of k-carrageenan immobilization, and to study the protective effect of cell immobiSurvival of freeze-dried Lactobacillus acidophilus immobilized in k-carrageenan gel