CONICET | Buscador de Institutos y Recursos Humanos

The currently intensive animal production requires the use of high protein diets. Many bacteria possess protease and peptidase actives that could act on some proteins and peptides present in wheat, soybeans and other grains. This could contribute to the production of amino acids and small peptides in the intestine of poultry fed with grains and seeds. In the formulation of probiotic supplements for both human and animal consumption, strains of the genera Lactobacillus and Enterococcus have been generally used as they are members of the normal intestinal microbiota and most of them considered GRAS microorganisms (generally regarded as safe).The aim of this work was to isolate Enterococcus sp. and Lactobacillus sp., present in the conventional poultry feed components and determine its proteolytic activity on a soybean protein extract.Soybean meal, meat flour and conventional poultry feed were the matrix for the isolation on different media (MRS, LAPTg and others). Gram stain, catalase and several biochemical tests were performed, in addition to verify absence of gelatin liquefaction and spore formation, and 12 strains were selected for further studies. A soybean protein isolate (SPI) was prepared to evaluate the proteolytic activity of the isolates and used as the only source of protein in a modified culture medium. This media was inoculated with each bacterial isolate and incubated for 8 h. Neutral pH was maintained with NaOH (1M) during incubation. The SPI hydrolysis by non-proliferating cell was also studied after 4h Incubation. The proteolytic activity was evaluated by Bradford for proteins (mg/mL) and o-ftaldialdehide (OPA) technique for the free amino acid determination (mM Glu/mL). The results were expressed as the difference (Δ) between the initial and final values obtained for each isolate after 8h of incubation.All isolated were able to grow in a culture medium with SPI instead of peptones. After 8h of incubation, some isolates reached 1 log unit above its initial values. Total protein showed decreased concentration in all isolates. However, from the twelve isolates only four presented positive differences by OPA suggesting that, in those where negative balances were observed, amino acid and small peptides released were consumed.Non-proliferating cells were able to degrade the SPI after 4h incubation, from 4mg/mL at the beginning to 1 mg/mL at the end of incubation, which indicates that proteolytic enzymes could be located in cellular wall of bacterium. The results indicated that isolated bacteria that evidenced the ability to hydrolyze SPI and release non-consumed amino acids could be used as probiotic supplements to collaborate in the proteins digestion and nutrient absorption of poultry.