Pilot-Scale Production of Hrp Proteins from Xanthomonas euvesicatoria and Their Evaluation on Disease Control Under Greenhouse Conditions and Agronomic Performance in the Field

Harpin (Hrp) proteins from Xanthomonas euvesicatoria represent a promising class of eco-friendly biocontrol inputs, yet their success depends on stable and scalable production systems. In this study, we evaluated the pilot-scale production of Hrp proteins (BioFensa) using the BV801 strain across two optimized platforms: solid-state fermentation (SSF; patent MX420963) and liquid-state fermentation (LSF, patent application MX/a/2025/002981). To optimize expression, Capsicum annuum tissue was integrated into both platforms as an eliciting substrate to simulate the natural plant–pathogen interface. Results demonstrated that SSF achieved a 3.28-fold higher biomass-normalized protein yield (Y p/x) and a 1.44-fold higher total protein yield than LSF. While both platforms produced functionally stable Hrp proteins, BioFensa derived from SSF reduced bacterial spot severity in C. annuum by approximately 60% at a low concentration of 0.01 μg mL−1 (p ≤ 0.05). Subsequent field trials confirmed safety and evaluated agronomic performance under natural conditions in the absence of disease pressure. These findings establish the technical feasibility of scaling Hrp protein production and underscore BioFensa as a promising, eco-friendly alternative for managing bacterial spot disease.