Secretory expression and fermentation optimization of recombinant porcine epidermal growth factor in Saccharomyces cerevisiae

Porcine epidermal growth factor (PoEGF) promotes intestinal epithelial development and enhances immune function in weaned piglets, offering potential as an alternative to in-feed antibiotics. However, large-scale application of recombinant PoEGF (rPoEGF) is hindered by high production costs and complex purification requirements. In this study, we constructed a recombinant Saccharomyces cerevisiae INVSc1 strain capable of expressing and secreting rPoEGF through the integration of an α-factor signal peptide-PoEGF-6 × His expression cassette. Expression was confirmed by SDS-PAGE and Western blot analysis, and bioactivity was validated using a BALB/c 3T3 fibroblast proliferation assay, yielding a maximum mitogenic activity of 10,963 U/mL. To improve production efficiency, a two-stage fermentation strategy was developed and optimized in a 4-L bioreactor. The process consisted of a glucose-based fed-batch growth phase followed by galactose-induced expression under optimized conditions (25 °C, pH 5.0, DO 30 %). This approach enabled high-cell-density cultivation (OD₆₀₀ ≈ 71.5) and achieved a final secreted protein yield of 30.2 mg/L. Notably, the culture containing active rPoEGF could be directly applied as a functional feed additive without the need for downstream purification. These results provide a practical, scalable, and cost-effective approach for producing bioactive rPoEGF and support its future application in swine production as a safe, antibiotic-free growth promoter.