Promotes Positive Probiotic Balance Supports Immune System NOW Acidophilus Three Billion is a real-time lab-tested acidophilus. Because some strains of acidophilus are more stable than others, scientists have developed a proprietary method that optimizes growth medium during fermentation. This method uses specific fermentation and drying techniques to ensure that each batch has the hardiest strains of this important probiotic. Natural color variation may occur in this product. The probiotic strain in this product has been identity-verified using DNA-fingerprinting technology.