Efficient Expression of Small Molecule Bioactive Peptides in Bacillus licheniformis.

Stable expression of γ-Glutamyltranspeptidase (GGT)-BPC157 and mScarlet-BPC157 in Bacillus licheniformis strain 2709 by chromosomal integration. Fermentation conditions were optimized using single-factor and orthogonal experiments to maximize yield. Under optimal conditions (2% inoculum, 40 g/L soybean peptone, and 80 g/L glucose), reporter-based expression signals increased approximately threefold compared to the basal medium. The fusion proteins were purified by fractional ammonium sulfate precipitation; optimal saturations were 50% and 60%, respectively. Biological activity was assessed in a rat model of ethanol-induced acute gastric ulcer. Both proteins showed gastroprotective and therapeutic activity, with ulcer inhibition rates ranging from 75.3% to 82.9% protective regime and 80.4% to 84.6% therapeutic regime. Histological analysis showed that the treatment reduced mucosal inflammation and stimulated glandular repair. ELISA showed significant downregulation of proinflammatory cytokines TNF-α, IL-1β, and IL-6 in gastric tissue. These results suggest a biotechnological production strategy for BPC 157 and applications for gastric ulcer treatment.