This invention relates to dual roles of the pepper esterase protein as a biocontrol agent that can elicit defense reactions in plant cells and as direct fungal inhibitor that can block fungal penetration into plant cells. The possible enzymatic actions of the PepEST protein were elucidated in both fungus and plant to gain insight into the molecular mechanisms involved in the fungal resistance. Exogenously treated PepEST protein on the unripe pepper fruits decomposed the cuticles of the fruits and released glycerol and 9-octadecenamide. The treatment resulted in the massive generation of hydrogen peroxide in the unripe pepper fruit and simultaneously elicited the expression of defense-related genes in both absence and presence of the fungus.