After oral administration, LBL released 5‐ASA in the presence of colonic bacterial azo‐reductases, which significantly reduced the expression of IL‐6 and IL‐1β and TNF‐α and myeloperoxidase (MPO), effectively inhibited ulcerative colitis and enhanced the colonization of LGGs, thereby acting as a regulator of the intestinal microflora. The gene discussed is MPO; the disease is ulcerative colitis.