Signal Peptide Selection for the Efficient Periplasmic and Secretive Expression of Recombinant Brazzein in Escherichia Coli

Background: The high production cost and difficulty of functional expression of brazzein are the limiting factors, making the development of inexpensive, scalable technologies critical for their successful implementation in the market. Secretory expression allows functional expression of the S-S bond-rich proteins and facilitates the purification procedure, resulting in lower processing costs. However, extensive screening and optimization of multiple signal peptides are required to ensure the successful secretion of recombinant proteins. Objective: We studied the expression of the minor type of brazzein using 21 different signal peptides in Escherichia coli and investigated their ability to direct the target protein into periplasmic space and culture medium. Methods: The synthetic genes were cloned into the pSEVA234 vector under the inducible Trc promoter and initial micro-scale expression analysis was conducted at two distinct conditions followed by scale-up and purification of the selected signal peptides with secretive abilities. Results: Two signal peptides led to the secretion of the target protein. The yields of the target protein for MalE_Brazzein and HstI_Brazzein in the periplasm were 11.33 mg/L and 52.33 mg/L, and those in the culture media were 3.975 mg/L and 7.73 mg/L, respectively. Conclusion: This study will provide insights into the identification of optimal signal peptides for secretive brazzein expression in E.coli and demonstrate that the abovementioned two signal peptides can be used for successful extracellular production of the target protein in this host.