Food-protein enzymatic hydrolysates possess both antimicrobial and immunostimulatory activities: a "cause and effect" theory of bifunctionality.

The antimicrobial activity (the ability to activate the microbial autolytic system) and immunostimulatory activity (the ability to improve the phagocytic cell functioning) of 20 food-protein hydrolysates [five food proteins (casein, alpha-lactalbumin, beta-lactoglobulin, ovalbumin and serum albumin) hydrolyzed with four gastrointestinal proteinases (trypsin, alpha-chymotrypsin, pepsin and pancreatin)] were examined. All the food-protein hydrolysates acted antimicrobially in vitro towards all 24 microbial strains tested: autolysis of 20 naturally autolyzing strains was activated, with the autolysis activation index (K(A)) ranging from 1.04 to 22.0, while autolysis was induced to values of 2.81-56.7% in four naturally nonautolyzing strains. When given to mice per os, all the food-protein hydrolysates enhanced the phagocytosing capacity of peritoneal macrophages, with the enhancement index (K(I)) ranging from 1.02 to 1.41. A direct correlation between K(A) and K(I) was observed. We make the presumption that K(I) is a function of K(A).