Construction and Modification of an Efficient Whole-Cell Catalyst for 5-Aminolevulinic Acid Using Induced Protoporphyrin IX as a Marker

5-Aminolevulinic acid (5-ALA) is a high-value and high-demand functional amino acid. The exploration of engineering approaches for biosynthesis using whole-cell catalysts as a promising production strategy is often limited by the lack of high-throughput evaluation platforms. Therefore, this study explored the correlative relationship between the fluorescence properties of 5-ALA-induced protoporphyrin IX (PpIX) and 5-ALA production in Escherichia coli (E. coli). Then, as a high-throughput screening platform, the expression of key genes hemA^C5 and hemL was balanced, and the favorable mutation strategy of the key enzyme GluTR was explored. In addition, the efficiency of 5-ALA synthesis was improved by "transferring" and "throttling" of downstream metabolism. Finally, the engineered strain MGRΔB^GTG yielded 1.494 g/L in a 5 L fermenter. This work provided a new indirect evaluation method for constructing the 5-ALA whole-cell catalyst capacity and a mining model for engineering approaches.