Antioxidant properties of bioactive metabolites produced by lactic acid bacteria isolated from tropical fruits.

Lactic acid bacteria (LAB) have been widely used in the production of fermented foods since the early stages of civilization, playing a key role in the development of sensory characteristics and in food preservation. In recent years, scientific interest in these microorganisms has increased due to their potential health benefits, including their contribution to the balance of intestinal microbiota and the strengthening of the immune system. Moreover, the exploration of the potential of these microorganisms and their metabolites as antioxidant and antimicrobial agents in the food industry remains limited, particularly when they are isolated from tropical fruits. The present study aimed to identify and characterize LAB isolated from Brazilian fruits. The isolated strains were evaluated for safety through analyses of hemolytic activity, production of biogenic amines, mucin degradation, antibiotic susceptibility or resistance, and enzyme production. Genetic analyses were also performed to investigate the presence of virulence genes. Strains considered safe were further subjected to stability and survival assays under simulated conditions of the gastrointestinal tract and oral cavity, as well as to evaluations of cell surface hydrophobicity and extraction of exopolysaccharides (EPS), in order to identify compounds associated with antioxidant activity. A total of thirteen LAB isolates were obtained from tropical fruits, all of which demonstrated potential for application as natural antioxidants. These findings contribute to the selection of putative probiotic strains isolated from fruits of the Brazilian biome, such as blackberry, cashew, cherry of Rio Grande (cereja-do-Rio-Grande), guava, red lemon, and pitanga, with promising prospects for safe use related to their antioxidant properties.