the 2 l starter of streptococcus thermophilus cbt st was cultivated for 12 hours while maintaining a ph level of 6 0 with ammonia then the bacteria cultures and residual protein were precipitated and concentrated after the fermented solution was fed into a continuous centrifuge at a flow rate of 60 l hr separately 10 l of cryoprotectant aqueous solution containing 0 5 kg trehalose 0 5 kg mannitol and 0 5 kg malto dextrin and 1 5 kg skim milk was prepared and sterilized under pressure in addition 3 l of polysaccharide aqueous solution was prepared by dissolving 15 g xantan gum and 15 g cellulose followed by sterilization of the solution under pressure the concentrated bacteria cultures were introduced into a mixture of the cryoprotectant solution and the polysaccharide solution prepared as described above then fed into a stirrer to form a homogenized solution stirring at 5 000 rpm this homogenized solution was frozen rapidly to u2212 55 u00b0 c and lyophilized at a temperature ranging of 0 to 40 u00b0 c it was found that the double coated lactic acid bacteria produced by protein coating using skim milk and polysaccharide coating using xantan gum and cellulose showed improved stability in the acceleration test acid resistance and bile resistance as compared to the non coated lactic acid bacteria results of the above test are shown in table 2 for bifidobacterium longum cbt bg powders which are double coated the protein aqueous solution was prepared by suspending 2 kg of isolated soybean protein in 100 kg water and added was an enzyme solution which was prepared by dissolving 5 4 g of proteolytic enzyme.