Design and pharmacodynamic study of live biotherapeutic products with efficient degradation of branched-chain amino acids.

The homeostasis of branched-chain amino acids (BCAAs) plays a crucial role in maintaining health, and the accumulation of BCAAs can lead to various diseases. Therefore, exogenous degradation or conversion of excessive BCAAs may help alleviate diseases caused by BCAA accumulation, such as maple syrup urine disease. This study utilized synthetic biology approaches to engineer two strains for efficient BCAA catabolism successfully-ECN-Deg and ECN-Tra-by integrating specific metabolic pathways into the chassis strain, Escherichia coli Nissle 1917 (ECN). ECN-Deg integrates a metabolic module for BCAA degradation, while ECN-Tra integrates a metabolic module for BCAA transformation. Both engineered strains demonstrate efficient BCAA catabolism in vitro and in vivo. In a high-BCAA mouse model, ECN-Deg and ECN-Tra alleviated liver and ileal damage caused by excessive BCAAs and reduced systemic inflammation levels. Furthermore, ECN-Deg and ECN-Tra were able to modulate the gut microbiota, increasing the richness of Akkermansia muciniphila and Mucispirillum schaedleri, which are associated with health benefits. Additionally, they reduced the richness of the pathogenic bacterium Streptococcus pasteurianus. Thus, this study lays the foundation for the development of probiotics for the treatment of BCAAs metabolic disorders and BCAAs-related chronic diseases.