CONICET | Buscador de Institutos y Recursos Humanos

Biopeptides are fragments encrypted in a precursor protein. They possess a particular amino acid sequence and specificbiofunctional attributes that can influence the main systems of an organism when released by proteolysis. Glycinin and βconglycinin are the main proteins in soybean (which in turn is the main protein source in poultry feeds), and many aminoacidic sequences with different features, such as antioxidant properties, are included in them. On the other hand, microorganisms are an important source of proteolytic enzymes. They could act on soybean proteins and release biofunctionalpeptides that may possess antioxidant properties. Therefore, the aim of this work was the study of the antioxidant activity ofthe biopeptides released from soybean protein isolate (SPI, which contains only glycinin and β-conglycinin) by three lacticacid bacteria (Enterococcus italicus LET 302, E. faecium LET 303 and Lactobacillus brevis LET 216) previously isolatedfrom soybean flour. To this end, each strain was incubated for 16 h in broth with SPI as the sole protein source. Then, thesupernatants were recovered by centrifugation and sterilized by filtration with 0.22 µm pore membranes. In order to obtaindifferent peptidic fractions, the supernatants were centrifuged with 10 kDa filters, and the filtrates were centrifuged again with3 kDa filters. This way, three fractions were obtained for each strain: M1 (peptides > 10 kDa), M2 (3 kDa < peptides < 10kDa), and M3 (peptides < 3 kDa). Protein concentration was assessed by Bradford, and the amount of protein on each fractionwas adjusted to 0.3 µg before the antioxidant activity was determined by DPPH assay. Antioxidant activity was observed onthe three fractions from all strains, and M3 presented the highest activity in all cases. Comparing the respective fractions fromdifferent strains, higher antioxidant activity was always showed by E. faecium LET 303, followed by E. italicus LET 302 andL. brevis LET 216. In conclusion, the proteolytic enzymes expressed by the strains of lactic acid bacteria studied could act onsoybean proteins, releasing peptides with antioxidant activity. The hydrolysis of these proteins, in a treatment before theirconsumption by poultry or in situ by these bacteria administered as feed additive, could improve their digestion as well ascollaborate with the oxidative metabolism of cells in the digestive system.