Park et al. [41] engineered E. coli MG1655 (MG1655-BCD-BUT) and EcN (EcN-BCD-BUT) to produce butyric acid and showed a significant amelioration of the DAI score and lower expression of IL-6 and MPO in the colonic tissue of DSS-induced colitis models. The gene discussed is MPO; the disease is colitis.