Preparation of 1,4-dihydroxy-2-naphthoic acid

The Propionibacterium (Propionibacterium) genus, 1,4-dihydroxy-2-naphthoic acid out intracellularly raised, by collecting the, 1,4-dihydroxy-2-naphthoic acid in a high concentration obtaining a composition containing. The composition improves the intestinal flora, which is effective in preventing improvement and metabolic bone disease abdominal discomfort seen upon ingestion of milk.