Engineered mini-tags boost liraglutide precursor expression to 133 mg/L in *E. coli*

Glucagon-like peptide-1 (GLP-1) agonists, like liraglutide, are crucial for managing type 2 diabetes mellitus due to their glucose-dependent insulinotropic activity. However, the small size of GLP-1 and its analogs, typically 31 amino acids, makes them highly susceptible to proteolytic degradation when expressed in microbial systems such as Escherichia coli. This susceptibility leads to low yields and increased production costs, posing a significant challenge for scalable and economical manufacturing of these therapeutic peptides.

Researchers investigated the use of engineered mini-tags to drive aggregation-driven expression of liraglutide precursors in Escherichia coli. They screened 11 different tags, evaluating their impact on fusion protein expression levels. The primary goal was to identify a tag that could maximize the yield of the liraglutide precursor. Expression levels were quantified, and the final liraglutide precursor was purified using RP-HPLC to determine the actual recovered yield.

Among the 11 mini-tags tested, the LP8 tag, a compact 4.0 kDa protein, demonstrated the highest expression efficiency. This tag achieved a fusion protein expression yield of 133 mg/L in Escherichia coli. Based on the mass fraction, the calculated liraglutide precursor yield from this fusion protein was 60 mg/L, representing 45% of the total fusion mass. After subsequent RP-HPLC purification, the actual recovered yield of the liraglutide precursor was 14.6 mg/L. This method effectively mitigated the proteolytic degradation typically observed with small peptide expression. > The LP8 mini-tag significantly improved liraglutide precursor expression, yielding 133 mg/L of fusion protein and 14.6 mg/L of purified liraglutide precursor.