Disclosed is a formulation for preserving the life of probiotic bacteria during passage through the stomach, while permitting their release in the intestine, and which has a low water activity and correspondingly long shelf life. These formulations are designed to retain potency up to the product expiration date. The formulation includes a substantially water-free mixture of probiotic bacteria with monovalent alginate salts, wherein the mixture has been formed and is maintained in a substantially water-free environment. The alginate salts include sodium-alginate and potassium alginate, but not divalent salts such as magnesium alginate or calcium alginate. Generally, an enteric coating (e.g., gelatin or cellulose encapsulation) for the formulation is provided.