High-level secretory production of leghemoglobin and myoglobin in Escherichia coli through inserting signal peptides

Leghemoglobin (LegH) and myoglobin (Mb) are both food additives that improve coloring and flavoring of meat analogs. With the rapid development of meat analog industry, the demand for LegH and Mb is increasing. However, the production of LegH and Mb is still limited. Here, high-level secretory production of LegH and Mb was achieved in E. coli through optimizing the expression conditions and introducing signal peptides. The strain containing Pel B signal peptide increased the LegH protein yield by 3.01-fold and the peroxidase activity was also improved. The LegH protein yield of strains containing signal peptides Pho A and Omp A was increased to 1.25 and 1.22 times, respectively. The secretion of SsMB fused with Pel B and Omp A was increased to 2.06 and 1.17 times, respectively. Moreover, the peroxidase activity of both proteins remained unaffected or even exhibited improvement. By optimizing the cultivation conditions for the engineered strain, there was a significant enhancement in the total protein content of LegH and SsMB, with an increase of 64% and 142%, respectively.